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Engineering 
Library 



GAS ANALYSIS 



s> 

THE MACMILLAN COMPANY 

NEW YORK BOSTON CHICAGO DALLAS 
ATLANTA SAN FRANCISCO 

MACMILLAN & CO., LIMITED 

LONDON BOMBAY CALCUTTA 
MELBOURNE 

THE MACMILLAN CO. OF CANADA, LTD. 

TORONTO 



GAS ANALYSIS 



BY 
L. M. DENNIS 

M 

PROFESSOR OF INORGANIC CHEMISTRY 
IN CORNELL UNIVERSITY 



THE MACMILLAN COMPANY 

1913 

Att rights reserved 



Engineering 
Library 



COPYRIGHT, 1902, 1913, 
BY THE MACMILLAN COMPANY. 



Set up and electrotyped. Published March, 1902. Reprinted 
October, 1906; June, 1910; September, 1911; September, 1912. 

New edition, April, 1913. 



/v. 



Koriaooti 

J. 8. Cushing Co. Berwick & Smith Co. 
Norwood, Mass., U.S.A. 



PREFACE 

In general plan this book follows the last edition of the English 
translation of Hempel's Methods of Gas Analysis, It was indeed 
begun with the intention of having it serve as a new edition of 
that work, but the many advances in the field of gas analysis 
during the last fourteen years have necessitated the incorpora- 
tion of much new material and the modification or excision of 
many of the older methods. In view of this fact, a new book has 
been written. 

With the kind permission of Professor Hempel, full descrip- 
tions of his classic methods for both technical and exact gas 
analysis have been incorporated in the present work, although 
in some cases the apparatus and the manner of its manipulation 
have been modified. 

Procedures for the determination of most of the gases that 
will be met with in analytical work are given in considerable 
detail. Although no attempt has been made to include descrip- 
tions of all of the new methods that have recently appeared, 
references to original articles are given throughout the work 
in order to assist the reader in obtaining more complete informa- 
tion upon the various topics than could be included in a labora- 
tory manual. 

The separation of the gases of the argon group has not been 
discussed for the reason that rapid and simple analytical methods 
for the determination of these several gases have not as yet been 
perfected. 

Certain methods of exact analysis that are adapted to specific 
determinations have been described, but the greater part of the 
book is devoted to rapid methods of technical gas analysis be- 
cause it is in this division of the field that most of the work of the 
gas analyst will lie. 



vi PREFACE 

In gas analysis the accuracy of the determination is probably 
dependent to a greater degree upon the manipulatory skill with 
which the work is performed than in any other branch of chemi- 
cal analysis. It is for this reason that the manipulation of each 
of the more generally used types of apparatus is described at 
length. 

I desire here gratefully to acknowledge the assistance that has 
been given me by my colleague Dr. R. P. Anderson to whom I 
am indebted not only for the preparation of the greater portion 
of the chapter dealing with the combustion of gases, but also for 
many valuable suggestions and for a careful reading of the proof- 
sheets. I take pleasure also in expressing my indebtedness to 
Mr. F. H. Rhodes for his skillful assistance in the testing of 
several of the new methods of analysis that are here described. 

L. M. DENNIS. 

ITHACA, NEW YORK, 
February, 1913. 



CONTENTS 

CHAPTER I 

THE COLLECTION AND STORAGE OF GASES 

PAGE 

Drawing off the Sample I 

Sampling Tubes 3 

Aspirators 7 

The Mercury Pump 8 

The Topler Pump 9 

Method of Working the Topler Pump 12 

Collection of Gas from a Mercury Pump 13 

Collection of Gases from Springs. 15 

Collection of Gases Dissolved in Liquids 16 

Collection of Gases from Reactions in Sealed Tubes 21 

Extraction of Gases from Minerals 21 

Gasometers 23 

CHAPTER II 

THE MEASUREMENT OF LARGE SAMPLES OF GAS 

Gas Meter 28 

The Rotameter 32 

CHAPTER III 

THE MEASUREMENT OF GASES 

The Reduction of the Volume of a Gas to Standard Conditions 33 

The Law of Boyle 33 

The Law of Charles 33 

The Lunge Gas Volumeter 37 

The Bodlander Gas Baroscope 40 



viii CONTENTS 

CHAPTER IV 

THE DETERMINATION OF THE SPECIFIC GRAVITY OF A GAS 

PAGE 

The Determination of the Specific Gravity of a Gas 

with the Apparatus of Bunsen . 44 

with the Apparatus of Schilling 46 

with the apparatus of Pannertz 47 

CHAPTER V 

ARRANGEMENT AND FITTINGS OF THE LABORATORY 

Laboratory for Gas Analysis 49 

CHAPTER VI 

APPARATUS FOR GAS ANALYSIS WITH WATER AS THE CONFINING LIQUID 

The Hempel Simple Gas Burette 51 

The Hempel Simple Absorption Pipettes 53 

The Hempel Simple Absorption Pipette for Liquid Reagents. ........ 53 

The Hempel Simple Absorption Pipette for Solid and Liquid Reagents 55 

The Hempel Double Absorption Pipettes 56 

The Hempel Double Absorption Pipette for Liquid Reagents 56 

The Hempel Double Absorption Pipette for Solid and Liquid Reagents 58 

Manipulation of the Hempel Apparatus 59 

Saturation of Confining Water 59 

Filling Burette with Confining Liquid 59 

Measurement of 100 cc 59 

Absorption of a Gas 61 

Absorbing Power of a Reagent 65 

Accuracy of Analyses with the Hempel Apparatus 67 

Running Down of Confining Liquid 68 

Portable Hempel Apparatus 69 

The Modified Winkler Gas Burette 70 

Manipulation of the Winkler Burette 71 

The Honigmann Gas Burette 72 

Manipulation of the Honigmann Burette 73 

The Bunte Gas Burette 74 

Manipulation of the Bunte Burette 74 

The Orsat-Dennis Apparatus 78 

Manipulation of the Orsat-Dennis Apparatus 87 



CONTENTS ix 
CHAPTER VII 

THE HEMPEL APPARATUS FOR EXACT GAS ANALYSIS WITH MERCURY AS THE 

CONFINING LIQUID 

PAGE 

Apparatus with Rubber Connections and Glass Stopcocks 90 

Gas Burettes with Correction for Variations in Temperature and Bar- 
ometric Pressure 90 

The Absorption Pipettes 96 

The Simple Mercury Absorption Pipette 96 

The Simple Mercury Absorption Pipette for Solid and Liquid Reagents 97 

The Mercury Absorption Pipette with Absorption Bulb 97 

Apparatus for Exact Gas Analysis without Rubber Connections or 

Stopcocks 99 

The Measuring Apparatus 101 

The Measuring Bulb 103 

Gas Pipettes for Liquid Absorbents 105 

Gas Pipettes for Solid Absorbents 107 

The Absorption 109 

CHAPTER VIII 

THE CONSTRUCTION AND CONNECTION OF APPARATUS 

Glass Blowing 113 

Mounting of Apparatus 114 

Rubber Connections 114 

Lubrication of Stopcocks 115 

CHAPTER IX 

PURIFICATION OF MERCURY 

Purification of Mercury by Nitric Acid 118 

Purification of Mercury by Concentrated Sulphuric Acid and Mercurous 

Sulphate 119 

Purification of Mercury by Distillation 119 

CHAPTER X 

ABSORPTION APPARATUS FOR USE WITH LARGE VOLUMES OF GAS 

The Friedrichs Spiral Gas Washing Bottle 123 

The Winkler Absorption Apparatus . 124 



x CONTENTS 

CHAPTER XI 

THE COMBUSTION OF GASES 

PAGE 

Possibilities and Limitations of the Combustion Method 127 

Gaseous Hydrocarbons and Nitrogen 136 

Identification of Gaseous Hydrocarbons 138 

CHAPTER XII 

THE DETERMINATION OF GASES BY COMBUSTION 

Analysis by Explosion 141 

The Explosion Pipette for Technical Gas Analysis 141 

Proportion of Gases in Analysis by Explosion : 143 

Formation of Oxides of Nitrogen 144 

Induction Coil 144 

The Hydrogen Pipette 144 

Oxyhydrogen Gas Generator 145 

The Explosion Pipette for the Hempel Apparatus for Exact Analysis. . 146 

Analysis by Combustion 147 

Combustion with an Electrically Heated Platinum Spiral 147 

The Combustion Pipette 147 

Manipulation of the Combustion Pipette 149 

Formation of Oxides of Nitrogen in Combustion Pipette 152 

Combustion with a Platinum Capillary Tube 154 

CHAPTER XIII 

PROPERTIES OF THE VARIOUS GASES AND METHODS FOR THEIR DETERMINATION 

Oxygen 158 

Properties of Oxygen 158 

Determination of Oxygen 158 

Determination of Oxygen by Combustion 159 

Determination of Oxygen with Copper Eudiometer 159 

Determination of Oxygen by Absorption 160 

Alkaline Pyrogallol 160 

Solid Phosphorus 163 

Phosphorus in Solution 166 

Copper .' 166 

Solutions of Ferrous Salts. . .168 



CONTENTS xi 

PAGE 

Sodium Hyposulphite 168 

Chromous Chloride 169 

Ozone 170 

Properties of Ozone 170 

The Detection of Ozone 170 

Examination of the Gases Produced by Burning Hydrogen in Air .... 175 
Examination of the Gases Produced by the Silent Electric Discharge in 

Air and Oxygen 1 76 

Examination of Gases Produced by the Action of Concentrated Sul- 
phuric Acid upon Barium Dioxide 177 

Examination of the Gases Produced by the Slow Oxidation of Phos- 
phorus in Moist Air 178 

Examination of the Gases Produced by the Action of the Flaming 

Electric Arc upon Air 178 

Examination of Atmospheric Air 178 

Determination of Ozone 179 

Hydrogen 181 

Properties of Hydrogen 181 

Detection of Hydrogen 181 

Determination of Hydrogen by Absorption 182 

Determination of Hydrogen by Explosion 186 

Determination of Hydrogen with Combustion Pipette 187 

The Absorption of Hydrogen by Palladium-black 188 

The Fractional Combustion of Hydrogen 191 

Fractional Combustion of Hydrogen with Platinum or Palladium 

Asbestos 192 

Fractional Combustion of Hydrogen with Palladium Black 196 

Fractional Combustion of Hydrogen with Copper Oxide 198 

Nitrogen 206 

Properties of Nitrogen 206 

Absorption of Nitrogen 207 

Nitrous Oxide _ . . 213 

Properties of Nitrous Oxide < ! 213 

Detection of Nitrous Oxide 213 

Determination of Nitrous Oxide 214 

Nitric Oxide 217 

Properties of Nitric Oxide 217 

Detection of Nitric Oxide 218 

Determination of Nitric Oxide 219 

Determination of Nitrites in the Atmosphere 222 

Nitrogen Tetroxide 223 

Properties of Nitrogen Tetroxide 223 



xii CONTENTS 

PAGE 

Ammonia 224 

Properties of Ammonia 224 

Detection of Ammonia 224 

Determination of Ammonia 224 

Carbon Dioxide 225 

Properties of Carbon Dioxide 225 

Determination of Carbon Dioxide 225 

Carbon Monoxide 226 

Properties of Carbon Monoxide 226 

Detection of Carbon Monoxide by Blood Spectrum 226 

Detection of Carbon Monoxide by means of Iodine Pentoxide 231 

Determination of Carbon Monoxide by Absorption 231 

Determination of Carbon Monoxide by means of Iodine Pentoxide ... 235 

Colorimetric Determination of Carbon Monoxide 237 

Determination of Carbon Monoxide by Fractional Combustion 239 

Methane 240 

Properties of Methane 240 

Determination of Methane 241 

The Heavy Hydrocarbons 246 

Absorption of Heavy Hydrocarbons 246 

Ethylene 248 

Properties of Ethylene 248 

Determination of Ethylene by Absorption 249 

Determination of Ethylene in presence of Acetylene 249 

Separation of Ethylene from Benzene 250 

Separation of Ethylene from Butylene. 250 

Propylene 250 

Acetylene 250 

Properties of Acetylene 250 

Determination of Acetylene 251 

Benzene 253 

Determination of Benzene 253 

Absorption of Benzene by Alcohol 253 

Absorption of Benzene by Paraffin Oil 254 

Determination of Benzene as Dinitrobenzene 254 

Separation of Benzene from Ethylene 255 

Absorption of Benzene with Nickel Solution. 255 

Naphthalene 260 

Determination of Napthalene 260 

Cyanogen 262 

Properties of Cyanogen 262 

Detection of Cyanogen 262 



CONTENTS xiii 

PAGE 

Determination of Cyanogen 263 

Detection and Determination of Cyanogen in presence of Hydrogen 

Cyanide 265 

Hydrogen Cyanide 269 

Properties of Hydrogen Cyanide 269 

Detection of Hydrogen Cyanide 269 

Determination of Hydrogen Cyanide 269 

Hydrogen Sulphide 270 

Properties of Hydrogen Sulphide 270 

Detection of Hydrogen Sulphide 271 

Determination of Hydrogen Sulphide 272 

Sulphur Dioxide 273 

Properties of Sulphur Dioxide 273 

Determination of Sulphur Dioxide 274 

Determination of Sulphur Dioxide in presence of Nitrous Acid. 276 

Carbon Oxysulphide 277 

Properties of Carbon Oxysulphide 277 

Determination of Carbon Oxysulphide 279 

Fluorine 280 

Determination of Fluorine 280 

Chlorine 284 

Properties of Chlorine 284 

Determination of Chlorine 285 

Hydrogen Chloride 289 

Properties of Hydrogen Chloride 289 

Determination of Hydrogen Chloride 289 

Silicon Tetrafluoride 290 

Phosphine 290 

Properties of Phosphine 290 

Determination of Phosphine 291 

Arsine 291 

Properties of Arsine 291 

Detection of Arsine * 293 

Determination of Arsine . 293 

Stibine .* 293 

CHAPTER XIV 

FLUE GAS ANALYSIS 

Sampling of Flue Gas 296 

Analysis of Flue Gas 297 

Automatic Flue Gas Analysis 299 



xiv CONTENTS 

PAGE 

The Carbon Dioxide Recorder 299 

The Autolysator 302 

The Gas Refractometer 304 



CHAPTER XV 

ILLUMINATING GAS FUEL GAS 

Coal Gas Pintsch Gas Water Gas Producer Gas Blast-Furnace 
Gas Natural Gas 

Coal Gas 306 

The Determination of the Illuminating Power of Coal Gas 307 

The Determination of the Specific Gravity of Coal Gas . ...... 309 

The Gas- Volumetric Analysis of Coal Gas 309 

The Determination of the Absorbable Gases 310 

Carbon Dioxide 311 

Benzene 312 

Other Heavy Hydrocarbons 312 

Oxygen 313 

Carbon Monoxide 313 

Hydrogen, Methane (and Ethane), and Nitrogen 314 

Nitrogen 317 

The Determination of Naphthalene in Coal Gas 318 

The Determination of Total Sulphur in Coal Gas 319 

Determination of Sulphur by Drehschmidt-Hempel Method 320 

Determination of Sulphur by Referees' Method 324 

Young's Volumetric Method for Determination of Sulphur 327 

The Determination of Cyanogen in Coal Gas 328 

Pintsch Gas 328 

Producer Gas Blast-Furnace Gas 330 

CHAPTER XVI 

THE DETERMINATION OF THE HEATING VALUE OF FUEL 

The Determination of the Heating Value of Solid Fuels 331 

The Bomb 331 

Preparation of Sample of Coal 333 

The Calorimeter 335 

Preparation of the Bomb 337 

Combustion of the Sample , 339 



CONTENTS xv 

PAGE 

The Water Equivalent of the Calorimeter 340 

Standard Combustible Substances 341 

Example of the Determination of the Water Equivalent of a Calorimeter 342 

The Radiation Correction 343 

Example of the Determination of the Heating Value of a Sample of Coal 345 

The Determination of the Heating Value of Liquid and Gaseous Fuels 347 

The Junkers Gas Calorimeter 347 

Preparation of Calorimeter 349 

Determination of the Heating Value of a Gas 351 

Calculation of Results 352 

Gross and Net Heating Value 354 

Automatic Gas Calorimeter 354 

CHAPTER XVII 

ACETYLENE GAS 

Impurities in Commercial Acetylene 355 

Sampling of Calcium Carbide 356 

Determination of Hydrogen in Acetylene 356 

Determination of Ammonia in Acetylene 356 

Determination of Phosphine in Acetylene 357 

Determination of Volume of Acetylene evolved from Sample of Carbide 363 

Calculation of Results 364 

Determination of Sulphur in Acetylene 367 

Determination of Silicon Hydride in Acetylene 368 

Determination of Carbon Monoxide in Acetylene 369 

Determination of Methane in Acetylene 369 

Determination of Oxygen and Nitrogen in Acetylene 369 

CHAPTER XVIII 

EXAMINATION OF ATMOSPHERIC AIR 

Composition of Atmospheric Air 370 

Determination of Moisture in the Atmosphere 371 

Absolute and Relative Humidity 371 

Wet and Dry Bulb Thermometers 371 

The Whirling Psychrometer 372 

Manipulation of the Whirling Psychrometer 373 

Calculation of Results 374 

The August Psychrometer 375 

The Hygrodeik 375 



xvi CONTENTS 

PAGE 

Determination of Carbon Dioxide in the Atmosphere 376 

Methods employed in Determination of Carbon Dioxide in Air 377 

The Hesse Method 377 

Solutions used in the Hesse Method 378 

Collection of Samples of Air 379 

Manipulation 379 

Calculation of Results 381 

The Pettersson-Palmqvist Method 382 

Anderson's Modification of the Pettersson-Palmqvist Apparatus 387 



CHAPTER XIX 

THE ANALYSIS OF SALTPETER AND NITRIC ACID ESTERS (NITROGLYCERINE, 
GUN-COTTON) WITH THE NITROMETER 

The Nitrometer 393 



CHAPTER XX 

THE LUNGE NITROMETER 

The Lunge Nitrometer 397 

Manipulation of the Lunge Nitrometer 398 

The Standardization of Potassium Permanganate 400 

The Determination of Active Oxygen in Hydrogen Dioxide 401 

The Determination of the Available Chlorine in "Chloride of Lime". . 401 

The Evaluation of Pyrolusite 402 

The Determination of Carbon Dioxide in Sodium Carbonate. 403 



International Atomic Weights, 1913 405 

Theoretical Densities of Gases 406 

Reduction of a Gas Volume to o and 760 mm 407 

Tension of Aqueous Vapor from 2 + 34 411 



GAS ANALYSIS 

CHAPTER I 
THE COLLECTION AND STORAGE OF GASES 

Drawing off the Sample. The collection of a sample of gas 
from a pipe, conduit, or furnace is usually accomplished by 
inserting into the chamber a tube of suitable material and 
drawing off the gas either into a sampling tube or bottle, or 
directly into the apparatus in which the gas mixture is to be 
analyzed. If the gas is at a comparatively low temperature, 
it may be drawn off through a tube of glass, and this material 
or porcelain must of necessity be employed if the gases are of an 
acid character. At temperatures below 300 a small lead pipe 
will be found convenient because of its flexibility. At higher 
temperatures iron, porcelain, or quartz tubes may be used. If 
the gases are very hot, the tube should be surrounded by a 
second tube through which cold water is kept circulating. 

A satisfactory form of such a tube is that described by Wink- 
ler in 1885. 1 It consists of the tubes A, and C, Fig. i, and a 
third tube, lying between A and C, to which the side arm B 
is attached. The tubes are made of metal, either copper or 
iron being usually employed. 2 The tube A, through which the 
gas sample is drawn, is about 5 mm. internal diameter. The 
tubes are kept cool by running water which enters through B, 
flows through C and escapes through the outlet D. A tube of 
glass or lead carrying a short side tube is attached to A, and 

1 Lehrbuch der technischen Gasanalyse, ist ed., p. 9. 

2 Frazer and Hoffman, Bulletin 12, Bureau of Mines, suggest the use of an inner 
tube A of quartz. 

I 



2 GAS ANALYSIS 



its lurvtier end is' connected with an aspirator. The sample of 
gas to be analyzed is drawn off through this tube into the 
sampling tube or gas burette, as desired. 

Gas mixtures that are to be subjected to chemical analysis 
should never be passed through long pieces of rubber tubing. 
Rubber is not only porous, but it may also absorb certain con- 
stituents of the gas mixture. These absorbed gases or even the 
air that a fresh piece of rubber tubing contains will cling tena- 
ciously to the walls of the tube, and when a gas mixture of other 
composition is passed through the tube they will slowly but 
continuously mix with the entering gas. If for any reason the 
use of a long piece of rubber tubing cannot be avoided in the 
collection or transfer of a sample of gas, the rubber tube should 
be vigorously rolled between the palms of the hands while the 



B 
FIG. i 

sample is flowing through it, in order to detach the gas adhering 
to its walls. The gas that passes through the tube during this 
operation should of course be discarded. 

When short pieces of rubber tubing are used for connecting 
tubes of other material, the ends of the tubes should be brought 
together under the rubber connector. 

A sample of the gaseous products of combustion from a 
heating apparatus should be drawn from the back of the fire 
chamber: further up in the flue the gas will usually be found to 
contain a considerable quantity of air because of the porosity 
of the wall. 

A gas mixture flowing through a pipe is frequently of varying 
composition from the middle of the pipe toward its sides. For 



THE COLLECTION AND STORAGE OF GASES 3 

this reason the sample tube that is inserted into the gas main 
should extend across the pipe or channel from side to side and 
have a fine longitudinal slit or a series of small holes through- 
out nearly its entire length in the main so that the sample drawn 
off will show as nearly as possible the average composition of 
the gas. 1 

Sampling Tubes. If the place where the gases are to be 
collected is directly accessible, as, for example, in the examina- 
tion of mine gases, small sampling tubes made in the laboratory 
from easily fusible glass tubing may be employed. The form 
used by Hempel in his researches "upon the composition of the 
atmosphere at different parts of the earth" is shown in Fig. 2. 
d is about 4 mm. thick; a, 6, and c, only i mm. These tubes were 
heated in an air bath in the laboratory to 200, and were then 



FIG. 2 FIG. 3 

exhausted with a mercury air-pump and fused at c. By simply 
breaking the tube at &, it fills instantly and completely with the 
air in question. The tubes are then closed for a few moments 
with a rubber cap, and are sealed off at a over a candle. The 
exhausting with the air-pump has the advantage of rendering 
one less dependent upon the care of the person who fills the tubes. 
If, however, it is desired to avoid this exhausting, the tubes 
are given the following form (Fig. 3). To fill such a tube, the gas 
to be examined is drawn through it and the tube is then sealed at 
a and b by fusion in a candle flame. 

Such tubes can safely be shipped by packing them in saw- 
dust in boxes that have a separate compartment for each tube. 
The boxes themselves are placed in a larger box filled with hay. 

A somewhat more convenient tube for collecting gas samples 
and transporting them to the laboratory for analysis is that 

1 See Metallurgical and Chemical Engineering, 9 (1911), 303. 



4 GAS ANALYSIS 

shown in Fig. 4. The tubes used in the Cornell laboratory vary 
from 16 cm. x 3.5 cm. (capacity about no cc.) to 25 cm. x 4.5 cm., 
the stopcocks have a bore one mm. in diameter, and the tube 
ends beyond the stopcocks are capillary tubes of six mm. ex- 
ternal diameter, one mm. bore, and about four cm. long. If the 
stopcocks are well made and carefully lubricated, and are fast- 
ened securely in place after the tube is filled with the gas, a 
sample may be kept for a considerable length of time in such a 
tube without undergoing appreciable change, provided the gas 
mixture does not act upon the lubricant of the stopcocks. 

In equipping a laboratory it is also well to provide some of 
these sampling tubes with tailstoppers (Fig. 5). Such stop- 





FIG. 4 

cocks render easy the elimination 
of the dead space in the end capil- 
lary tubes when the sample is trans- 
ferred to the gas burette (see p. 59) FlG - 5 
but as they are more liable to leak than are the single bore 
stopcocks, tubes that are fitted with them, while more use- 
ful in the laboratory, are not so well suited to the transport of 
gas samples. 

These tubes are filled with the gas sample by drawing it 
through the tube until the air that was originally in the tube 
is entirely displaced. Naturally this presupposes that large 
amounts of gas are at one's disposal. If only a small quantity of 
gas is available, the tube is first filled with water or mercury 
and this is then displaced by the gas. Water can be used only 
when it is first saturated with the gas mixture that is being 
sampled and if any of the constituents of the gas mixture are 



THE COLLECTION AND STORAGE OF GASES 




H 



fairly soluble in water, as, for example, ammonia or carbon 
dioxide, mercury must be employed even if only approximately 
accurate results are desired. 

It is frequently the case that an average sample of the gases 
passing through a flue or pipe during a period of several hours is 
desired. Since carbon dioxide is always present in flue gases, 
mercury must be used as the confining liquid in the sample 
tube. The weight and costliness of mercury make 
it necessary that the sample tube be small, and this 
in turn renders it imperative that the dead space 
between the sample tube and main tube be elim- 
inated and that it be impossible for the gas in B 
the sampling tube to diffuse back into the main 
tube or to be drawn back into the main by a sud- 
den drop in the pressure. These conditions are 
fulfilled by the clever device of Huntly l which is 
shown in Fig. 6. The tube 2 is first filled with mer- 
cury up to the top of the bore of the upper stop- 
cock, and both stopcocks are closed. The capil- 
lary A is then connected with the branch from 
the main tube, and the stopcock turned so that 
A communicates with B. The air in A is thus 
driven out through B. If the pressure in the main 
is less than that of the atmosphere, suction must 
be applied at B. The upper stopcock is then 
turned through 180 to connect A with C, and the 
lower stopcock is carefully opened to such an 
extent as will give the desired speed of flow. 
Huntly states that "it has been found by trial that the rate 
at which the gas is drawn in is constant throughout within one 
per cent." 

1 /. Soc. Chem. Ind., 29 (1910), 312. 

2 Huntly does not give the dimensions of the tube. If the wide part of the tube 
were about 18 cm. long and 3.5 cm. diameter, it would contain quite a little more 
than 100 cc., an amount sufficient for the analysis. 




FIG. 6 




FIG. 7 



THE COLLECTION AND STORAGE OF GASES 7 

If the tube is to be shipped to the laboratory after the sample 
has been taken, some mercury should be left in the capillary 
tube above the stopcock K, and the tube should be placed in a 
frame that will support it in an upright position. 1 

Aspirators. If the gases to be collected have a pressure less 
than the prevailing atmospheric pressure, an aspirator must be 
employed to draw them over into the sampling apparatus. The 
simplest form of aspirator consists of two interchangeable bottles 
of equal size and of the same width of neck. If it is desired to 
draw off a sample of gas for analysis while the mixture is being 
aspirated the arrangement shown in Fig. 7 may be employed. 
The water flows from the bottle A through the siphon tube G 
into the lower bottle C, and by so doing draws the gas through 
the tube F. When the bottle A is empty C, which is now full, 
may be put in its place and the aspirating of the gas continued. 
The gas burette is connected to a T-tube in the manner shown, 




FIG. 8 

is filled to the horizontal tube at c by opening the pinchcocks 
d and /and raising the level-tube, and is then filled with a sample 
by lowering the level-tube to the position shown in the figure. 
The pinchcocks d and / are then closed and the rubber tube 
attached to the burette is slipped off from' the small glass tube e 
which joins the two short pieces of rubber tubing. 

Small rubber suction bulbs, Fig. 8, may at times be found 
useful for drawing a gas mixture into the sampling tube, which 

1 In Bulletin No. 12 of the Bureau of Mines (IQII) Frazer and Hoffman describe a 
sampling tube that is patterned after that of Huntly, but is inferior to the latter in 
that it does not carry the double stopcocks which facilitate the elimination of the 
dead space in the capillary tubes. 



8 



GAS ANALYSIS 



should be placed before the bulb to avoid contact of the rubber 
with the gas. If running water is available, a water suction 
pump of glass (Fig. 9) or the more compact and durable Chap- 
man pump of brass, may be used for this purpose. 

If running water is not at hand a suction 

pump and rubber pressure bulb may be used 

for drawing the gas 

through the appara- 
i tus. Fig. 10 shows 

such an arrange- 
ment, 1 the rubber 

pressure bulb being 

here attached to 

a Finkener suction 

pump. The rubber 

tube on the side 

arm of the pump 

is joined to the 

apparatus through 

which the gas is to 

be drawn. This de- 
FIG. 9 vice is superior to 

the rubber suction 
pump in that stronger suction is 
obtained and the bulb does not 
come in contact with the gases 
which, if of corrosive nature, would 
soon destroy it. 

With such an apparatus as that constructed by Korting, 2 
steam also may be used for aspirating. 

The Mercury Pump. A mercury pump is at times needed 
for the exhaustion of sample tubes like those described on p. 3, 
and for the removal and collection of gases in certain operations 

1 Ojferhaus, J.f. Gasbeleuchtung, 53 (1910), 806. 
2 Gebr. Korting Akt.-Ges., Kortingsdorf near Hanover. 




FIG. 10 



THE COLLECTION AND STORAGE OF GASES 



such as that described on p. 22. 
Of the many forms of mercury 
pumps that have been designed, 
that of Topler is one of the most 
satisfactory. The construction and 
operation of the pump have been 
clearly described by Travers, from 
whose book on the "Experimental 
Study of Gases" the following de- 
scription is quoted: 

" The Topler Pump. The 
pump-chamber A (Fig. n) is 
made of stout glass, and should be 
about 200 mm. long and 50 mm. 
in diameter; the ends, and partic- 
ularly the upper end, should be 
tapered considerably to meet tubes 
of about 13 mm. in diameter. If 
the upper end of the pump- 
chamber presents a surface ap- 
proaching to the horizontal to the 
mercury as it rises to the pump- 
head, films or even bubbles of air 
may be entrapped between the 
mercury and the glass, and ex- 
haustion will be slow. The side- 
tube which joins the vertical tubes 
at F and H should also be of 
about 13 mm., diameter; the in- 
ternal angle between the two tubes 
at the upper junction should, for 
the reasons given above, be very 
acute. The tube C, through which 
the gas enters the pump, should 
be much narrower than the side- 




FIG. ii 



io GAS ANALYSIS 

tube, 4 mm. is a convenient diameter; if it is not made so 
the gas which enters the pump while the mercury is still fall- 
ing, may carry the whole of the mercury in the side-tube into 
the upper part of the pump, and cause a serious fracture. If 
the pump is properly constructed, the gas will rise in bubbles 
between the mercury and the glass. 

"The vertical tube F at the top of the pump-chamber, should 
be tapered to meet the capillary tube (7, which should be bent 
on itself in a continuous curve of about 3 cm. in diameter imme- 
diately above this point. The length of the capillary tube should 
be about 800 mm., and its internal diameter should not much 
exceed one mm. ; it should be turned up at its lower end so as to 
admit of collecting gases through the pump. The capillary tube 
may easily be replaced when broken if a sufficient length of tube 
is left above the junction at F. A piece of tube, of the same diam- 
eter as the vertical tube of the pump, is first sealed to a straight 
piece of capillary tube of sufficient length. The tube is worked 
in the blowpipe flame till a perfectly even tapered junction is 
obtained; it is then bent, cut to the right length, and sealed to 
the pump-head with the aid of a small blowpipe. The efficiency 
of the pump will depend to a great extent on the care which is 
expended on this part of it. 

"The lower vertical tube should be so long, about 800 mm., 
that when there is a vacuum in the pump and the mercury 
stands below the level of the joint H, the lower end of it lies 
below the level of the mercury in the reservoir, or air may slowly 
leak into the pump through the junction with the rubber tube. 
The rubber tube should not be longer than is necessary to allow 
of the reservoir being raised to the level of the pump-head, 
and its internal diameter should be nearly as large as that 
of the glass tube to which it is attached so as to allow of the 
free flow of the mercury. In order to obviate any chance of the 
rubber tube bursting, it should be sewn into a strip of leather 
or inclosed in a piece of hollow cotton lamp- wick. 1 

1 These precautions are quite unnecessary if enamelled rubber tubing is employed. 



THE COLLECTION AND STORAGE OF GASES n 

"In order to prevent the mercury from passing into the tube 
D, containing pentoxide of phosphorus, when the reservoir is 
raised, the tube C may be carried vertically upwards to a height 
of about 900 mm. and then bent on itself. It is more convenient, 
however, to employ a glass valve V as in the figure, and it is 
probable that the rate of exhaustion of a piece of apparatus 
attached to the pump would be considerably decreased by the 
interposition of the long glass tube. The valve should be ground 
so that its upper surface fits sufficiently accurately into the inner 
surface of the tube containing it to hinder the passage of the 
mercury; the angle between the two surfaces should be very 
obtuse, or the valve may tend to remain closed after the mercury 
has fallen. The top of the valve should be on a level with the 
junction F (Fig. n), so that the mercury closes it before it 
reaches the capillary tube. 

"The tube D containing the pentoxide of phosphorus 1 is 
usually connected with a large two-way stopcock T, so that the 
pump may be used in connection with more than one piece of 
apparatus. 

"The pump may be fixed to a stout board as in the figure. 
The block K is cut so that the bottom of the pump-chamber 
rests on it, and is kept in place by means of a strip of brass 
and a couple of screws. 

" The fall-tube passes through a hole in the bottom of the 
tray; a cork fitting closely to the fall- tube serves to keep it 
firmly in place, and to prevent the escape of mercury through 
the hole. The tray supports the basin into which the end of 
the capillary tube dips. The board to which the pump is 

1 This reagent is almost universally used as a dehydrating reagent in working 
with gases, but it is somewhat difficult to obtain pure. The oxide should be per- 
fectly white and quite free from discolored nodules and sticky masses of meta- 
phosphoric acid. When exposed to the air it should deliquesce without turning red 
or giving off any odor. The principal impurities consist of the lower oxides of 
phosphorus, some of which are in themselves volatile and react with gases, such as 
chlorine and ozone, and with water vapor to yield phosphoretted hydrogen. The 
pentoxide can be obtained absolutely free from the lower oxides by throwing it into 
a red-hot porcelain basin, and stirring it in a current of oxygen. 



12 GAS ANALYSIS 

attached may be screwed to the wall at a convenient height, 
or fixed to a stand. 

" The reservoir may be placed in a bracket, or supported in a 
retort ring with a piece cut out of it to allow of the passage of the 
rubber tube. The retort ring may be fixed to an iron rod passing 
through holes in the tray and stand. A pulley and cord may be 
found convenient in working large pumps. 

" Method of Working the Topler Pump. The pump is first 
carefully cleaned with chromic and sulphuric acids, washed with 
distilled water and alcohol and dried. It is then set up on the 
stand, the tube C is sealed to the tube D, containing pentoxide 
of phosphorus, and the rubber tube and reservoir B are attached. 
When sufficient mercury has been poured into the reservoir and 
trough the pump is ready for use. 

"The reservoir is raised so as to expel about two-thirds of the 
air in the pump-chamber through the capillary tube, and is 
then lowered. As the mercury falls the air in the tube containing 
the pentoxide forces its way through the mercury in the side 
tube, and enters the pump. The operation is then repeated, but 
during the first few strokes the air should not be completely 
expelled from the pump-chamber. If this precaution is not 
taken the air will begin to enter the side-tube, while it still 
contains a long column of mercury; it will not then break up 
into bubbles, but will probably carry the whole of the mercury 
upwards against the junction F causing a serious fracture. On 
no account should the tap T be opened while the mercury is 
falling in the pump-chamber, or a similar accident may result. 
In any case the gas should only be allowed to enter the pump 
slowly. A rapid current of gas may impact the pentoxide 
of phosphorus into the end of the tube containing it, and render 
subsequent exhaustion very slow. 

" During the last stages of the process of exhaustion care must 
be taken that the mercury does not come into violent contact 
with the top of the pump, or a fracture may result. The mer- 
cury may be allowed to rise rapidly to the junction F; it may then 



THE COLLECTION AND STORAGE OF GASES 




R 



be checked either by pinching the rubber tube or by lowering the 
reservoir. With practice the action becomes automatic. 

"When a pump is first set up it should be allowed to remain 
exhausted for a sufficient time 
for the complete absorption of 
water in the apparatus by the 
pentoxide of phosphorus. Fur- 
ther, since gases like carbon 
dioxide condense in considerable 
quantity on glass surfaces, the 
maximum efficiency will not be 
reached till the pump has been 
filled with air, and exhausted 
two or three times." 

Collection of Gas from the 
Mercury Pump. The method 
described by Travers for collect- 
ing the gases that are drawn by 
the pump from a container con- 
sists in filling a tube with mer- 
cury and inverting this over the 
end of the capillary tube G. 
According to Keyes l this pro- 
cedure is open to objection be- 
cause there is always present 
between the mercury and the 
walls of the connecting tube, a 
film of air that cannot, in the 
Travers' method of manipula- 
tion, be removed from the tube 
before the gas sample is driven 
into it. To remedy this diffi- 
culty Keyes fuses the sampling tube S, Fig. 12, to the upturned 
end of the capillary tube G, Fig. n. A small trap / is fused to 

1 /. Am. Chem. Soe., 31 (1909), 1271. 




FiG. 12 



14 GAS ANALYSIS 

the lower end of 5 and this is connected to the level-bulb M . 
At the upper end of ,5" is a double-bore stopcock N. If the mer- 
cury pump is to be used simply to exhaust a container, stop- 
cock N is left open to the air with the mercury standing at the 
level shown in the figure during the first few strokes. When the 
exhaustion of the apparatus is nearly complete, the level bulb M 
may be raised to expel the air from the tube S. The stopcock N 
is then closed and upon lowering the level bulb a fair vacuum 
will result in S which will facilitate the escape into this tube 
of the bubbles of gas passing downward through the capillary 
tube of the pump. 

To collect the gas that is discharged from the pump the tube 
5 is connected to a gas burette R by a bent capillary tube and 
short connectors of rubber tubing in the manner shown in the 
figure. Mercury is used as the confining liquid in R as well as 
in S. The level tube of the burette R is raised and the air in 
the burette is driven over into the collecting tube ,5. The stop- 
cock W of the burette is then closed and the air adhering to the 
walls of the burette is caused to collect at the top of the tube by 
lowering the level tube of the burette and thus bringing the 
tube under diminished pressure. The air thus released is ex- 
pelled from the burette by raising the level tube and opening 
the stopcock W. The air in the collecting tube 6* is driven out 
by first raising the level bulb M and driving out most of the air 
in the tube through the bore of the stopcock N that communi- 
cates with the open air. N is then closed, the level bulb is 
lowered, and the air thus liberated from the walls of the tube 5 
is driven out through the stopcock by raising M. Upon re- 
peating these operations several times the collecting tube and 
the gas burette may be rendered practically free from gas (air). 
The mercury pump is now started and the gas to be collected 
is driven over directly into the tube S. At the conclusion of the 
pumping this gas is passed over into the burette R by raising 
the level bulb M and turning the two stopcocks to the proper 
positions. Any minute gas bubbles that may have lodged 



THE COLLECTION AND STORAGE OF GASES 15 



between the mercury and the glass walls can easily be set free 
and recovered by the manipulation above described. 

Collection of Gases from Springs. To collect gas from 
springs that are directly accessible, the small apparatus pro- 
posed by Bunsen 1 may be used (Fig. 13). 

This consists of a test-tube c of from 
40 to 60 cc. capacity, drawn out at a be- 
fore the blast-lamp to the size of a fine 
straw, and connected air-tight with the 
funnel b by means of a well-fitting cork 
or a piece of rubber tubing. The ap- 
paratus is then filled with the water of 
the spring. This cannot be done without 
access of air, which would change the 
composition of the gases dissolved in the 
spring water in the tube. Hence the in- 
verted apparatus, with the mouth of the 
funnel upward, is lowered below the level 
of the spring, and, with a narrow tube 
reaching to the bottom of the test-tube, 
the water that in the first filling had 
come in contact with the air is sucked out 




FIG. 13 



until one is satisfied that it has been entirely replaced by other 
water from the spring. If now the gas of the spring is allowed to 
rise through the funnel into the test-tube thus filled, the purity 
of the sample is assured. If the rising bubbles stop in the neck 
of the funnel or at the contraction a, they can easily be made to 
ascend by tapping the edge of the funnel upon some hard sub- 
stance. The apparatus is then placed in a small dish and re- 
moved from the spring, and the tube is sealed by fusion at a. 
This can easily be done with the blow-pipe, the moisture at the 
point a having first been driven away by warming. 
W. Ramsay and M. W. Travers 2 have proposed the apparatus 

1 Bunsen, Gasometrische Methoden, 2d ed., p. 2. 

2 Proc. Royal Soc., London, 60 (1896). 442. 



i6 



GAS ANALYSIS 



shown in Fig. 14 for collecting large quantities of gases from 
mineral waters. The cylinder A is filled with the water of 
the spring, and the rising bubbles of gas pass into the cylinder 
through the funnel D and the tube C. 

Collection of Gases dis- 
solved in Liquids. For the 
determination of the volume and 
composition of the dissolved 
gases in liquids, the Tiemann 
and Preusse modification of 
Reichardt's apparatus 1 can be 
recommended (Fig. 15). 

This consists of two flasks A 
and B, each of about i liter 
capacity, and connected by 
tubes with the gas-collector C. 
The flask A is fitted with a per- 
forated rubber stopper in which 
is inserted the glass tube a bent 
at a right angle and ending flush 
with the lower surface of the 
stopper, a is joined by a piece 
of rubber tubing to the tube be, 
jjl which in turn connects with the 
gas-collector C. C is held by 
a clamp, has a diameter of 35 
mm., is about 300 mm. long, 
and at the upper end is drawn 
out to a short, narrow, and 




FIG. 14 



narrow, 

slightly bent tube that can be closed with the rubber tube and 
pinchcock g. In the lower end of C is a rubber stopper with 
two holes through one of which the tube be, projecting about 
80 mm. into C, is inserted. Though the other opening passes 
the tube d which extends only slightly beyond the stopper 

1 Berichte der deutschen chemischen Gesellschaft, 12 (1879), 1768. 



THE COLLECTION AND STORAGE OF GASES 17 

and connects C with the flask B. B has a double-bore rubber 
stopper carrying the tubes e and /. e ends about 10 mm. 
above the bottom of the flask, and above the stopper it is 
bent at a right angle and is connected with d. The tube /, 
which need not project below the stopper, carries a thin rubber 
tube x about i m. in length and provided with a mouthpiece. 
A pinchcock for closing the rubber tube between a and b is also 
needed. 




FIG. 15 

The apparatus thus arranged is made ready for a determina- 
tion by filling the flask B somewhat more than half full of boiled 
water and removing the flask A by slipping the tube a out of the 
rubber connection; then, by blowing into the rubber tube x, 
water is driven over from the flask B into the gas-collector 
C and the adjoining tubes, until the air is wholly displaced. 
The rubber tubes at b and g are now closed with pinchcocks. 
The flask A is then filled to the brim with distilled water, the 
stopper is inserted, water being thereby driven into the tube a, 
and the flask is again connected with b, the pinchcock being 
opened. 



1 8 GAS ANALYSIS 

The water in B is now heated to gentle boiling, and that in A 
is allowed to boil somewhat more rapidly. The absorbed air 
is thus driven out, and the gases which are dissolved in the water 
in A and C collect in the upper part of C, from which they are 
removed by occasionally opening the pinchcock at g and blowing 
into the rubber tube x. 

When, upon cooling the apparatus, the gases that have col- 
lected disappear, the heating of the flask A is discontinued, the 
pinchcock between a and b is closed, and A is disconnected and 
emptied. The water in C and B is now entirely free from ab- 
sorbed gases, and air cannot enter from without because the 
liquid in B is kept continually boiling. The apparatus is now 
ready for a determination, which is made as follows: 

The cooled flask A, whose capacity has previously been 
determined, is filled with the water to be examined, and the 
stopper is pressed in so far that the air in the tube a is completely 
driven out. a is then connected with b, care being taken that 
in so doing no air-bubbles are inclosed. The pinchcock between 
a and b is opened, and the water in A is heated to gentle boiling. 
The dissolved gases are hereby driven over into the gas-collector 
C. Steam is formed at the same time. The heating of the flask 
A must now be so regulated that the gas and steam evolved 
never drive out more than half the liquid in C: otherwise there 
is danger of gas-bubbles entering the tubes d and e and thus 
escaping. 

After heating for about twenty minutes, the flame under A 
is removed. In a few minutes the steam in A and C condenses, 
and water passes from B toward C and A. If a gas-bubble 
is observed in A , the flask A must again be heated and cooled in 
the manner just described. The operation is ended when the hot 
liquid flows back and completely fills A. The rubber tube g 
is then connected with a small tube which is filled with water 
or mercury, and the gas standing over the hot liquid in C is 
driven over into a eudiometer, gas burette, or gasometer by 
blowing into the tube x and opening the pinchcock g. 



THE COLLECTION AND STORAGE OF GASES 19 

F. Hoppe-Seyler 1 has devised a somewhat more complicated 
apparatus for extracting the dissolved gases from the waters of 
springs and rivers. It is a modification of the method proposed 
by Bunsen and Dittmar. The apparatus shown in Fig. 16 
varies slightly from that suggested by Hoppe-Seyler in that a 
gas burette D (see page 91) is used as the collecting vessel and 
air-pump. Any other burette with a two-way stopcock may, 




FIG. 16 

of course, be employed in place of the burette here figured. The 
apparatus consists of the gas burette D filled with mercury, 
the glass tubes, A, B, and C, and the level-bulb F. The tubes 
A, B, and C are joined together with pieces of rubber tubing. 
Screw pinchcocks are placed at a and b. To extract the dissolved 
gases from a sample of water, a bent glass tube is inserted at b 
and the tubes A and C are filled with mercury by raising the 

1 Zeitschr.f. analyt. Chem., 31 (1892), 367. 



20 GAS ANALYSIS 

level-bulb F, the mercury being allowed to rise until it reaches 
the tube which has been inserted at b. The glass tube is then 
introduced into the vessel that contains the water to be ex- 
amined, and by lowering the level-bulb F water is drawn into 
the apparatus until the tube A is completely filled with it. The 
bent tube is then removed from b, B is inserted in its place, and 
the pinchcock at b is closed. The two-way stopcock of the 
burette is now turned so that the burette communicates with 
the exit tube /. The air in the burette is driven out by raising 
the level-bulb E, and the stopcock g is then turned so that the 
burette communicates with the tube B. Upon lowering the 
level-bulb as far as possible the burette may now be made to 
function as a mercury air-pump and the air which is in B can be 
drawn over into D. Upon closing the stopcock g, raising the 
bulb E, and then turning G so that the burette communicates 
with /, the air which has been drawn out of B may be expelled 
from the burette. This operation is then repeated until no more 
bubbles of gas appear. When the tube B has thus been ex- 
hausted of air, the cocks a, b, and c are opened, and the water 
in the apparatus is brought to boiling by heating the tubes 
A and C directly with the Bunsen burner. The escape of the 
gas into the vacuum of B begins at once. After about five min- 
utes, the water in A is brought nearly to the height of the pinch- 
cock b by raising or lowering the level-bulb F. b is then closed 
and the gas in B is pumped out by raising and lowering the 
level-bulb E in the manner above described. / is connected 
by means of a bent capillary tube with a second gas burette or 
gas pipette, and the gas which has been drawn over into D 
from B is transferred to the second gas holder by turning g so 
that D communicates with /. The pinchcock b is then opened, 
the water in A is again brought to boiling, and the gas set free 
by this second treatment is added to the portion first obtained. 
By repeating the process three times it is easily possible to com- 
pletely extract all of the absorbed gases with the exception 
of carbon dioxide. This latter gas is so persistently retained 



THE COLLECTION AND STORAGE OF GASES 21 



by the water that according to the experiments of Jacobsen it 
is impossible to entirely remove it. Pettersson has shown that 
even after strongly acidifying the water with sulphuric acid 
the carbon dioxide cannot completely be driven out by 
boiling. 

Collection of Gases from Reactions in Sealed Tubes. - 
Gases are set free in many chemical reactions that take place in 
sealed tubes. If one 
wishes to examine these 
gases, Bunsen directs 1 
that when the tube is 
fused together, it be 
drawn out to a fine tip 
about 2 mm. wide and 
50 mm. long. To collect 
the gases given off, a 
mark is made at a 
(Fig. 17), with a sharp 
file, and the tip is con- 
nected with a capillary 
glass tube by means of 
a short piece of rubber 
tubing. 

For safety's sake wire 
ligatures are put on at b 
and c. On breaking the tube inside the rubber at a, the gas 
passes through the delivery tube and can be collected in any de- 
sired receiver. If very strong pressure in the tube is to be ex- 
pected, the rubber connection is surrounded with a strip of linen, 
and the tube itself is wrapped in a cloth. A third ligature put 
on at d makes it possible to stop the escape of gas at any time, 
the rubber forming with the broken-off glass tube a Bunsen 
rubber valve. 

Extraction of Gases from Minerals. To extract the gases 

1 Bunsen, Gasometrische Methoden, 2d ed., p. 10. 




FIG. 17 



22 



GAS ANALYSIS 



that may be present in minerals or rocks, Ramsay and Travers 1 
recommend that the mineral first be reduced to a fine powder 
and be then mixed with double its weight of primary potassium 
sulphate. The mixture is placed in a hard-glass tube which is 
connected with an air-pump. After the tube has been exhausted 
it is heated to redness with a large Bunsen burner. The es- 
caping gases are pumped out and are collected in a small tube 




FIG. 1 8 

that contains a small amount of a solution of 
potassium hydroxide. In order to exclude the 
possibility of leakage, the tube is joined to the air- 
pump in the manner shown in Fig. 18. As may 
be seen from the drawing, the large tube is drawn 
out at A , a piece of rubber tubing is placed over 
the end of the small tube B, and after it has been 

inserted in the contraction at A, the joint is cov- 
FIG. 19 

ered with mercury standing in the wide portion C. 

In most cases the gases that are present in the mineral are driven 
out by heating the substance alone without the addition of 
primary potassium sulphate. 

To collect the gases that are set free when minerals are heated 
in sealed tubes with sulphuric acid Travers 2 uses the tube shown 

1 Proc. Royal Soc., London, 60 (1896), 442. 
*Proc. Royal Soc., 64 (1898), 132. 



THE COLLECTION AND STORAGE OF GASES 23 

in Fig. 19. Sulphuric acid is first poured into the tube and the 
weighed sample of the finely powdered mineral is placed in a 
short tube that has a rod fused to the bottom of it to hold this 
sample tube above the surface of the acid. This tube is slipped 
into the large tube in the position shown in the figure, and the 
upper end of the outer tube is then drawn out, is connected with 
a mercury air-pump by means of a rubber tube, and is exhausted 




FIG. 20 

and sealed by fusion at C. After the contents of the tube has 
been heated for a length of time sufficient to completely decom- 
pose the mineral the tip of the tube is marked with a file at D, 
and the tube is again attached to the pump by a piece of rubber 
tubing. After the air in the connecting tube has been pumped 
out, the tip C is broken off inside the rubber tube and the gas 
is drawn out by means of a mercury pump and is collected for 
analysis. 

Gasometers. If a sample of gas is to be collected and kept 
for analysis for a considerable length of time, the portions of 



24 GAS ANALYSIS 

the gas taken for analysis must be displaced with mercury. 
Water may not be used for this purpose because its solvent 
power for gases would cause change in the composition of the 
gas mixture. A small gasometer that is suitable for prolonged 
storage of a gas sample is shown in Fig. 20. The large glass 
bulb A serves to hold the gas. At the top it carries the bent 




FIG. 21 



FIG, 22 



capillary tube a, and at the bottom it is joined to the level-bulb 
B by a rubber tube. The capillary is closed by a rubber tube and 
pinchcock. The apparatus is first filled with mercury. By 
lowering or raising the level-bulb, gas can be drawn in or driven 
out as desired. If gases are to be kept for some time, the capil- 
lary tube a is filled with mercury by means of a little pipette 
inserted at c. This closes the bulb perfectly. 



THE COLLECTION AND STORAGE OF GASES 25 

A convenient gasometer may easily be constructed from a 
round-bottomed flask fitted with a two-hole rubber stopper 
and bent glass tubes in the manner shown in Fig. 21. The 
thistle tube may be replaced by a level-bulb and rubber tube 
(see Fig. 20). 





For the collection and storage of large samples of gas, gasom- 
eters made of sheet zinc, of sheet iron or galvanized iron, 
or of glass may be employed. The form shown in Fig. 22 may 
also be used to aspirate the gas into the container. The large 



26 



GAS ANALYSIS 



gasometers that ordinarily are used in laboratories are not well 
adapted to the storage of gas samples for analysis because of 
the solvent action of water upon the constituents of the gas mix- 
ture. This defect may partially be remedied by using a concen- 
trated solution of sodium chlo- 
ride or of magnesium chloride as 
confining liquid or by bringing 
a layer of paraffin oil upon the 
surface of the water. 1 The 
solvent action of the confining 
liquid may also be lessened by 
using a gasometer of such form 
as will give small surface of 
contact between the gas mix- 
ture and confining liquid. An 
instrument of this type is 
shown in Fig. 23. 

The gasometer consists of the 
bell A which dips into the cylin- 
drical ring-shaped space B, this 
latter being filled with a solution 
of magnesium chloride. The 
shaded part D is a hollow cyl- 
inder closed at both the top 
and bottom. The iron tube a 
serves as a guide for the bell 

and should therefore be made quite wide. The gasometer is 
filled by introducing the gas in question through /. A branch 
tube at e extends downward into a glass cylinder filled with 
water and serves the double purpose of enabling the op- 
erator to observe the pressure of the gas and to drive out any 
air in the tubes through this branch. The weights E and F 
make it possible to regulate at will the pressure in the gasometer. 

1 See Voigt, Chemiker-Zeitung, 32 (1908), 1082, and Reinhardt, Chemiker-Zeitung, 
33 (1909). 206. 




FIG. 24 



THE COLLECTION AND STORAGE OF GASES 27 

When the gasometer has been filled, the rubber tube d is removed 
from c. The gas can then be drawn off through either the stop- 
cock b or c. 

A glass gasometer constructed on the same principle as the 
foregoing is shown in Fig. 24. 



CHAPTER II 
THE MEASUREMENT OF LARGE SAMPLES OF GAS 

When a gas is present in a gas mixture in only very small 
amounts, it is usually determined by drawing or forcing a large 
sample of the gas mixture through a suitable absorption appara- 
tus, and ascertaining the amount of the absorbed constituent 
by gravimetric or volumetric means. It is evident that under 
such circumstances the large size of the gas sample obviates 
the necessity of very accurately determining its volume (see 
page 122). 

An arrangement of apparatus that is suitable for the approxi- 
mate measurement of large gas volumes, and that can easily 
be put together from stock apparatus in the laboratory, is shown 
in Fig. 25. The large bottle B is filled with water, and the stop- 
per carrying the inlet tube and the siphon tube D is then in- 
serted in the neck of the bottle. D is filled with water by blow- 
ing into the inlet tube, and the screw pinchcock E is then closed. 
B is now connected with the absorption apparatus A through 
which the sample is to be drawn, and the pinchcock E is opened. 
When the first bubble of gas passes through the absorbent, a 
measuring cylinder C is placed under the end of the siphon tube, 
and the water drawn over from the bottle B is thus measured. 
After the operation is complete, the volume of gas represented 
by the water that has been measured off in the cylinder C is 
reduced to standard conditions and the percentage of the ab- 
sorbed constituent in the original gas volume is then calculated. 

Gas Meter. A more convenient but more expensive appara- 
tus for measuring large gas volumes is an Experimental Gas 
Meter 1 of the type shown in Fig. 26. 

1 These meters may be obtained from S. Elster, Berlin. 

28 



MEASUREMENT OF LARGE SAMPLES OF GAS 29 




FIG. 25 



30 GAS ANALYSIS 

meter and is filled by removing the cap M and pouring water 
into the opening until it flows out of the opening C in the lower 
part of the meter. The caps of both openings are then screwed 
firmly into place. The gas enters the meter at F, passes through 




FIG. 26 



the measuring drums, and escapes through the tube L. Its 
speed of flow may be delicately adjusted by a micrometer screw 
that turns the dial H. The manometer K shows the pressure 
of the gas. The dial of the meter is provided with two hands. 



MEASUREMENT OF LARGE SAMPLES OF GAS 31 




FIG. 27 



32 GAS ANALYSIS 

The shorter one A records the liters of gas that pass through 
the meter. The longer hand B makes one complete revolution 
for every three liters and is of use in the measurement of small 
gas volumes and also in the measurement of the amount of gas 
passing through the meter in a relatively short period of time. 

The Rotameter. A unique and useful device for measuring 
the volume of gas per hour that is flowing through a tube is the 
rotameter l shown in Fig. 27. It consists of a glass tube A through 
which the gas passes from below upward. The speed of flow of 
the gas current can be regulated by turning the stopcock B. 
Inside the glass tube there is a little float F which is carried 
upward by the flowing gas, and at the same time set in rapid 
rotation about its vertical axis. The float will rise or sink in 
the glass tube according to the amount of gas t'lat is passing 
through the tube, and the height of the float, which is measured 
by a scale attached to the tube, shows the number of liters of 
gas flowing through the tube per hour. The scale on the tube 
is an arbitrary one, and the instrument is calibrated for one 
particular gas. The rotameter is made in different sizes, the 
maximum flow of gas through the smallest size being about 
200 liters per hour, and through the largest size about 30,000 
liters per hour. 

1 This instrument may be obtained from the Rotawerke, Aachen, Germany. 



CHAPTER III 
THE MEASUREMENT OF GASES 

The quantity of a gas may be determined either by measuring 
its volume, or by ascertaining its weight, or by causing it to enter 
into chemical reactions that render possible its determination 
by indirect gravimetric or volumetric methods. Because of the 
comparatively low densities of gases, the first method is usually 
most accurate as well as most convenient. In fact in gas ana- 
lytic work the determination of the amount of a gas by direct 
measurement of its weight is but rarely employed. 

THE REDUCTION OF THE VOLUME OF A GAS TO STANDARD 
CONDITIONS 

The volume of a gas is affected by changes of pressure and of 
temperature. 

The Law of Boyle. The effect of change of pressure is ex- 
pressed in the Law of Boyle: Provided the temperature remains 
constant, the volume of a gas is inversely proportional to the pres- 
sure. 

VQ:V = p:pQ, or 

VQpo = Vp. (l) 

The Law of Charles. If a gas at o C. be warmed to i C. 
(the pressure remaining constant) it will expand ^TT f the vol- 
ume that it occupied at o. If the temperature of the gas be 
raised from o to 273, its volume will double. Similarly, if a 
gas be cooled below o, its volume will decrease ^-- of its vol- 
ume at o for each degree of fall of temperature below o. 
These facts are briefly stated in the Law of Charles: Provided 

33 



34' GAS ANALYSIS 

the pressure remains constant, the volume of a gas will change 
-g-y-g- or 0.00367 of its volume at o for each degree of change of 
temperature. If z> represent the volume of the gas at o and v 
the volume at a temperature t and a = YTS> 



v = v Q (i + a/), or 

|I|ii 1 * = rr^ " (2) 

Similarly, the volume v\ of the gas at a temperature t\ would 
from (2) be 

> or 
Consequently, 



+ o/i 

Vi 






Furthermore, if the volume of a^gas remains constant, its pres- 
sure will change ^\^ or 0.00367 of its pressure at o for each degree 
of change in temperature. 

p = po (i + at) 

or 



pi = po (i + d/i) or 

po ' 

i -t- "*i 

v>, 

(4) 

Since the effect of change of temperature is represented by 
the same formula whether pressure or volume is under con- 




THE MEASUREMENT OF GASES 35 

sideration, by combining (3) and (4) there is obtained the ex- 
pression 

( } 



i + at i + o/i 

In stating the volume of a gas it is agreed among scientists 
to express it in terms of the volume that the gas would occupy 
under certain arbitrary conditions (standard conditions) namely 
at a temperature of o C. and under a pressure of 760 mm. of 
mercury. To reduce an observed gas volume to the volume 
that it would occupy under standard conditions we may employ 
the formula (5). Since 



it must also be true that 
. If now po = 760 and to = O C. 



i + at i+ at 
then since a = 0.00367 

vp 

VQ 760 = or 

i + 0.00367^ 

VQ = v ; r (6) in which V Q 

760(1 +0.003670 

is the volume under standard conditions, z> the observed volume, 
p the observed pressure expressed in millimeters of mercury 
and t the observed temperature. 

By means of the above formula (6) a gas volume may 
correctly be reduced to standard conditions provided the gas, 
when measured, contains no water vapor. If, however, water 
vapor is present, a correction must be introduced. Every 
liquid tends to change to the gaseous state and the vapor of the 
liquid exerts a gas pressure which is termed the vapor pressure 
of the liquid. This vapor pressure is dependent upon the temper- 



36 GAS ANALYSIS 

ature and upon the nature of the liquid, but it is not affected by 
the pressure of other gases, nor by the amount of the liquid 
that is present. If a closed space is filled with a mixture of gases, 
each gas will exert a definite pressure which is the same whether 
it exists alone in the space or whether other gases are present. 
The total pressure of the gas mixture is the sum of the partial 
pressures of the various gases. If now a gas volume that con- 
tains water vapor is measured at atmospheric pressure, the 
partial pressure of the dry gas will equal the barometric pressure 
less the pressure of the water vapor in the gas. If the gas is not 
" saturated" with water vapor, the partial pressure of the latter 
is difficult to determine. But when a gas is measured over water, 
or over mercury upon which stands a small amount of water, the 
space is saturated with water vapor, and since the maximum 
pressure of water vapor at various temperatures is known (see 
table on p. 411) the pressure of the dry gas can easily be ascer- 
tained by noting the temperature of the gas and subtracting 
from the observed barometric pressure the pressure of water 
vapor at the observed temperature. Representing the pressure 
of the water vapor by m, and inserting this correction in formula 
(6), we obtain 

p / , 

760 ( i + 0.00367/ ) 

Inasmuch as the vapor pressures of liquids vary with the na- 
ture of the liquids, it is apparent that if a gas is measured over 
a liquid other than pure water the correction to be introduced 
for the vapor pressure of the liquid will not be the same as for 
that of pure water. For this reason those forms of apparatus in 
which gas volumes are measured over concentrated solutions of 
various absorbents will not yield accurate results unless the vapor 
pressure of each solution is known and taken into account. To 
avoid error from this source it is now customary, in the better 
types of apparatus, to pass the gas mixture from a measuring 
burette into a separate apparatus containing the absorbent, 



THE MEASUREMENT OF GASES 



37 



and to then draw the gas back into the burette where it comes 
into contact with water before being again measured. In this 
manner the space occupied by the gas is always saturated with 
water vapor when the volume 
of the gas is measured. 

When a gas is measured 
over dry mercury, the vapor 
pressure of the mercury is so 
small as to be negligible un- 
less the gas is measured at 
a temperature considerably 
above 40. 

THE LUNGE GAS VOLUMETER 

To facilitate work with the 
nitrometer (p. 397) Lunge has 
devised an instrument, the 
gas volumeter, with the aid 
of which a volume of gas in 
the measuring tube of the 
apparatus may quickly be 
brought to the volume that 
it would occupy under stand- 
ard conditions. This does 
away with the usual calcula- 
tions and effects a consider- 
able saving of time. 

The instrument, Fig. 28, 
consists of a gas burette A, 
a reduction tube B, and a 
level-tube C, which are con- 
nected at the lower ends by 
pieces of enamelled rubber 
tubing and the T tube D. 

The gas burette A has a 




3 8 GAS ANALYSIS 

capacity of somewhat more than 100 cc. and is calibrated from 
the stopcock downward in 100 cc. divided into f cc. At its 
upper end is a two-way stopcock S. The upper tubes of the 
stopcock are capillary and one of them is bent over and down- 
ward as shown in the figure. 

The reduction tube B is provided with a single bore stopcock 
at the upper end. Below the stopcock it is widened into a 
bulb. From the stopcock to a mark on the tube somewhat be- 
low the bulb the tube holds exactly 100 cc. From the 100 cc. 
mark downward the tube is calibrated to about 140 cc. in ^ cc. 

The level-tube C is a plain tube open at the top. The three 
tubes are fastened in clamps that are attached to the iron 
stand H. 

To prepare the apparatus for use it is first necessary to inclose 
in the reduction tube a volume of moist air that, under standard 
conditions and in the dry state, would have a volume of exactly 
100 cc. This is accomplished as follows: 

The apparatus is filled with clean mercury and somewhat 
more than 100 cc. of air is then drawn into the reduction tube 
B by opening the stopcock of the tube and lowering the level- 
tube C. A drop of water is next drawn into the bulb of B through 
the stopcock to insure that the space above the mercury in the 
reduction tube is saturated with water vapor. A thermometer 
is hung close to the apparatus, and after the apparatus has 
come to the temperature of the room, the thermometer and 
barometer are carefully read. 

The volume that 100 cc. of air, under standard conditions, 
would occupy under the observed temperature and pressure 
is now calculated from the formula 

760(1 +.003670 

V = VQ 

p m 
which is derived directly from (7) on p. 36, and in which 

VQ = 100 CC. 

The stopcock of the reduction tube is now opened, and the 



THE MEASUREMENT OF GASES 39 

level-tube is raised or lowered until the mercury in B stands 
exactly at the volume calculated for v. The stopcock of B is 
then closed. There is thus inclosed in the reduction tube a 
volume of air that will occupy exactly 100 cc. when measured 
under standard conditions. 

If now a gas is brought into the burette A, the volume that 
it would occupy under standard conditions may rapidly be 
ascertained in the following manner. 

The level-tube C is raised or lowered until the mercury in 
the reduction tube B stands close to the 100 cc. mark, and 
C is then clamped firmly in that position. The burette A is 
now raised or lowered until the mercury in it stands at the same 
height as that in the reduction tube and it is then clamped in 
position. This adjustment will usually cause the mercury to 
move up or down from the 100 cc. mark in B. It is brought 
back to the mark by again changing the height of the level-tube 
and the burette is again raised or lowered until the mercury 
in it and in B are at the same level. These adjustments are 
repeated until, with the mercury in A and B at the same height, 
the mercury in the reduction tube B stands exactly at the 100 cc. 
mark. 

Since the pressure upon the air in B suffices to bring it, at 
the now prevailing temperature, to the volume that it would 
occupy under standard conditions, it follows that the gas in the 
burette A *, if at the same temperature as the air in B, will also 
be brought to the volume that it would occupy under standard 
conditions, and consequently its corrected volume may be 
directly read off. 

The Lunge gas volumeter is open to criticism because the 
burette and the reduction tube stand free in the air and for 
that reason are subject to sudden and different changes of tem- 
perature. This may cause appreciable error since a difference 
of only i C. would mean a variation of 0.3 per cent in the gas 

1 The space above the mercury in A must be course of saturated with water vapor 
as is the space in B. 



40 GAS ANALYSIS 

volume. For this reason the apparatus will give dependable 
results only when it stands in a room of uniform temperature 
and free from drafts, and when in the manipulation great care 
is exercised to avoid the uneven warming of the tubes by heat 
from the hands or from the body of the operator. 

THE BODLANDER GAS BAROSCOPE 

Bodlander has devised 1 an ingenious instrument with the 
aid of which the weight of the gas in the measuring burette may 
be calculated in very simple manner from its pressure. 

A volume of gas v that is measured at f and under a pressure 
of p mm. may be reduced to the volume that it would occupy 
under standard conditions v according to the equation 

VX p X 273 



760 (273 + /) 

Since the weight of a cubic centimeter of a gas of the molecu- 
lar weight M is equal to 0.0446725 X M mg., the weight G of 
i) cc. of the gas 

v X p X 273 X 0.0446725 X M 
G = - - - - - mg. (i) 

760 (273 + /) 

If in all of the measurements the volume is adjusted so that 

760 (273 + /) 

v = -- - - cc. (2) 

273 x 0.0446725 x 100 

then equation (i) may be reduced to the simple form 

pxM 

G = - -mg (3) 

100 

If now an apparatus is so constructed and calibrated that the 
volume of a gas corresponding to equation (2) at a prevailing 
temperature of / may easily be ascertained, then the w r eight 
1 Z.f. angew. Chem., 1894, 425. 



THE MEASUREMENT OF GASES 



of the gas in milligrams may be 
determined by bringing the gas to 
this volume, ascertaining the pres- 
sure exerted by the gas, and multi- 
plying this pressure, expressed in 
decimeters, by the molecular 
weight of the gas. 

The instrument that Bodlander 
devised for this style of analysis 
is termed by him a gas baroscope. 
The essential parts of the appara- 
tus are shown in Fig. 29. The 
measuring tube consists of the 
bulb A which is about 7 cm. in 
diameter, and a tube B on which 
is marked a scale running from 
zero at the top to 30 near the bot- 
tom, each division being divided 
into fifths. A and B are sur- 
rounded by a water mantle. The 
upper end of the tube is closed by 
the two-way stopcock S that ends 
in the capillaries C and D. The 
capacity of the measuring tube 
from the lower side of the stopcock 
to the mark zero on the tube B is 
the volume at o calculated from 
equation (2) when / = o. The vol- 
ume down to division one is that 
at i calculated for / = i, and so on. 

The lower end of the measuring 
tube B is connected by a 
piece of enamelled rubber 

tubing with the level-bulb 

L which is provided with 



G- 





FIG. 



2Q 



42 GAS ANALYSIS 

a stopcock F and a bent tube G that is about 12 mm. internal 
diameter and projects about 27 cm. above the bulb. The con- 
tents of L is somewhat greater than that of the bulb A. The 
measuring tube and the level-bulb are fastened by clamps to 
an iron stand M that is about 1.2 meter high. The level-bulb 
L and the clamp that carries it may be slid up and down 
upon the rod in such manner that the tube G of the bulb lies 
close to the front of a -meter scale K that is divided into milli- 
meters and hangs in a perpendicular position from a clamp at- 
tached near the upper end of the rod. 

The measurements with the gas baroscope are made*in the 
following manner. The instrument is filled with clean mercury. 
The air in the bulb A is completely driven out through the capil- 
lary tube C by opening the stopcock S and raising the level-bulb. 
The capillary tube D is then connected with the evolution ap- 
paratus or the container that holds the gas that is to be measured 
and the gas is drawn into the bulb A by turning the stopcock 5" 
to proper position and lowering the level-bulb L. S is then closed 
and the level-bulb L is lowered until the gas in A and B is ex- 
panded to such a volume that the mercury in B stands at the 
mark on the scale that corresponds to the prevailing tempera- 
ture. The sharp adjustment of the mercury to this mark is ac- 
complished by lowering L until the mercury in B stands some- 
what below the mark, and then turning down the clamp H 
upon the rubber tube until the mercury is brought exactly to 
the proper height. The apparatus must contain such an amount 
of mercury that this will now stand in the tube G above the 
level-bulb. G itself stands close to the scale K, but should not 
be allowed to touch the scale and thus push it out of its per- 
pendicular position. The height of the mercury in G is now 
carefully read off on the scale K with the naked eye. This 
reading can be made to an accuracy of about one-tenth mm. 
but the readings are of course more accurate if made with a 
cathetometer. 

To ascertain the pressure exerted by the gas in A a second 



THE MEASUREMENT OF GASES 43 

reading is necessary. The gas is first driven out of A through 
the capillary tube C by opening S and raising the level-bulb. 
S is then closed and L is lowered until the mercury in the tube B 
stands at exactly the same position as before. The height of the 
mercury in G is then read off upon the scale, and the difference 
between this reading and the first reading on the scale expressed 
in decimeters and multiplied by the molecular weight of the gas 
gives the weight of the gas in milligrams. 

If a mixture of gases has first been introduced into the measur- 
ing tube and the weight of a constituent gas is desired, the 
pressure of the gas mixture is first ascertained in the manner 
above described, the capillary tube C is then connected with a 
suitable absorption pipette for the removal of the constituent 
in question, the gas mixture is driven over into this pipette and 
is then drawn back into A. The mercury in B is now again 
brought to the original mark, the pressure is read, and from 
the difference in pressure, the weight of the absorbed constituent 
is calculated. 

If the gas that is being measured is saturated with moisture, 
a drop or two of water should be introduced into A upon the 
mercury before the final measurement of the pressure, after 
the removal of the gas, is made. No correction for the tension 
of water vapor is then necessary. 



CHAPTER IV 

THE DETERMINATION OF THE SPECIFIC GRAVITY OF 

A GAS 

The determination of the specific gravity of a gas may con- 
veniently be made by Bunsen's method l of measuring the time 
of escape of the gas. 

This method is based upon the fact that the specific gravities 
of two gases- escaping through small openings in thin plates bear 
nearly the same ratio to each other as the squares of their times 
of escape. If a gas of the specific gravity s has a time of flow /, 
and another gas 'of a specific gravity si has a time of flow /i, 
the relation between the time of escape and the specific gravity 
is given by the equation 

si_ t 

s " t 2 ' 

If s or the specific gravity of one of the gases be regarded as i , 
the specific gravity of the other gas is found by the formula 



51 " 



Figure 30 shows the apparatus used for this determination. 
A glass tube of about 70 cc. capacity is luted into the iron 
cap A . This cap is fitted with a three-way stopcock by means of 
which the inside of the glass tube can be brought into communi- 
catiqn with either the tube B through which the gases are in- 
troduced, or the small opening in C. This opening is made in a 
platinum plate, which is about as thick as tin foil, and is luted 
in position. To obtain an opening as small as needed, the 

1 Bunsen, Gasometrische Methoden, 2d ed., p. 184. 
44 



DETERMINATION OF SPECIFIC GRAVITY OF GAS 45 



platinum foil is pierced with a fine sewing needle, and is 
hammered with a polished hammer upon a polished anvil 
until the opening can no longer be seen with the naked eye, 
and is visible only when the plate is held between the eye 
and a bright flame. The plate thus perforated is cut out in 
the form of a small circular disk, the 
opening being at the center. 

In order that the gases to be ex- 
amined may always escape through 
the opening C under the same con- 
ditions as regards pressure, there is 
placed in A a float bb. This float 
should be as light as possible, and for 
this reason it is best made from a very 
thin-walled glass tube. The float has 
at /3 a little button of black glass 
from which projects a small, white 
glass point. 

Two fine threads of black glass, fii 
and y8-2, are fused around the lower 
part of the stem of the float. These 
two threads, together with the black 
glass button at the top, serve as 
marks. 

If the tube containing the gas be 
pushed down so far into the mercury 
that a mark on the glass is tangent to 




FIG. 30 



the outer mercury surface, then the float which is inside the tube 
is no longer visible through the telescope. 

If now the stopcock be opened and the gas allowed to escape 
through the opening in the platinum plate, the float rises, being 
carried up upon the surface of the mercury in the tube. If the 
level of the external mercury be observed through the telescope, 
the white glass tip of the float soon comes into the field, and in- 
forms the observer that the black button {$ will shortly appear. 



4 6 



GAS ANALYSIS 



When this comes in sight the time is taken, the end of the timing 
being at that moment at which the mark ^82 comes into the field 
of the telescope; the near approach of ^82 is here shown by the 
appearance of j8i. 

From these observations is obtained the time of escape of a 
column of gas which, measured from /3, has the length shown 

by the marks $82 on the float; 
moreover, the gases escape under 
the same differences of pressure in 
all of the experiments. The times 
taken by the different gases to 
escape through the fine opening in 
C give, when squared, the ratios of 
the specific gravities of the gases. 

The gases must be dried, and the 
mercury must be pure and dry. 
An advantage of the Bunsen ap- 
paratus is that a determination can 
be made with a very small quantity 
of the gas. 

Schilling has given the apparatus 
a very practical form for the ex- 
amination of illuminating gas, 
where large amounts of the gas 
are usually available. 

A (Fig. 31) is a glass tube of 40 
mm. internal diameter and about 

450 mm. long. The upper end is 

luted into a brass cover C into 
which is inserted the tube B 

through which the gas is led in. The gas escapes through a per- 
forated platinum disk in the upper end of the tube D. A ther- 
mometer T is immersed in the water of the cylinder K. The 
inner cylinder has two marks, M and N. The apparatus is 
filled with water. 




FIG. 31 



DETERMINATION OF SPECIFIC GRAVITY OF GAS 47 



To determine the specific gravity of an illuminating gas with 
this apparatus, the tube is first filled with air, and the time of 
escape of the air, under the prevailing temperature and pressure, 
is noted. The last trace of air is then removed by repeatedly 
drawing in and driving out the 
gas to be examined, and the time 
of escape of the illuminating gas 
is then observed. The squares 
of the values are directly pro- 
portional to the specific grav- 
ities of the gases. Since the 
specific gravity of air is usually 
taken as i, the calculation is 
very simple. 

The Schilling apparatus is 
open to objection because of the 
inconvenience in filling the inner 
cylinder with the gas under 
examination. Moreover, the 
marks are so far apart as to ren- 
der the reading of them some- 
what awkward. These draw- 
backs are avoided in the mod- 
ification of the apparatus 
devised by Pannertz, 1 who uses 
two glass bulbs that are con- 
nected by a piece of rubber 
tubing (Fig. 32). The measure- 
ments are made with the flask at the right which has an iron 
cap C of the same general construction as that used with the 
Bunsen apparatus. The two marks A and B are placed upon 
the narrow necks of the bulb. The flask is filled with air or 
with the gas mixture by first raising the level bulb and filling 
the measuring bulb with water and then placing the measuring 

1 /./. Gasbeleuchtung, 48 (1905), 901. 




FIG. 32 



48 GAS ANALYSIS 

bulb on the stand D and drawing in the air or gas through the 
side arm of the iron cap. In measuring the time of escape of 
the air or gas, the measuring vessel is placed upon the stand E 
and the level bulb is placed upon the stand D as shown in the 
figure. When the apparatus is charged with the right amount 
of water, the water will rise above the upper mark B nearly 
to the iron cap. 



CHAPTER V 

ARRANGEMENT AND FITTINGS OF THE 
LABORATORY 

The room for gas analysis should have a northern exposure 
and should have wide windows. The working-table should 
run along the outer wall so that the operator may face the win- 
dow and be able to make his readings without being obliged to 
turn around toward the source of light. The floor should be 
of cement, and should slope slightly toward the middle in order 
that any mercury that may be spilled may easily be brought 
together and taken up. If the floor is of wood, it may 
be made mercury-tight by covering it with linoleum. The 
room should further be provided with gas and with running 
water and with a large sink. The sink should have an iron 
"S" trap, and the lower bend of this trap should be bored, 
threaded, and provided with a screw plug to permit of the easy 
removal of any mercury that may collect in the trap. 

There should also be an ample supply of water of the tempera- 
ture of the room. It is convenient to have this water piped to 
every working-place. This is cheaply accomplished by plac- 
ing near the top of the room and above the sink a galvanized 
iron tank containing 100 liters or more, and running from 
the lower part of this tank an iron pipe that passes along 
the tables. The tank is easily filled through a small iron pipe 
which hooks over its top and reaches down into the sink, 
where it may be connected with the faucet by a piece of rubber 
tubing. 

The laboratory should also contain a mercury air-pump, a 
barometer, accurate thermometers, and water suction-pumps 
at the working-tables. An electric current is necessary, and 

49 



50 GAS ANALYSIS 

this may be supplied either by a battery or storage cells, or 
the direct current from a dynamo may be utilized. A small 
induction coil is needed for analysis of gas mixtures by explo- 
sion. It is desirable to have narrow shelves fastened to the 
wall upon which to place the Hempel pipettes. 



CHAPTER VI 

APPARATUS FOR GAS ANALYSIS WITH WATER AS THE 
CONFINING LIQUID 

THE HEMPEL SIMPLE GAS BURETTE (Fig. 33) 1 

This consists of two glass tubes, A and B, which are set in 
iron feet, F and D, and are connected by a rubber tube of 7 mm. 
internal diameter, 12 mm. external diameter, and about 120 cm. 
long. To facilitate the cleaning of the burette the rubber tube 
may be divided in the middle and the two ends joined by a 
piece of glass tubing. 

Inside the feet the tubes A and B are bent at right angles 
and conically drawn out. The end projecting from the iron 
is of about 4 mm. external diameter and is somewhat corrugated, 
so that a rubber tube may be tightly fastened to it by wire 
ligatures. 

The measuring tube A ends at the top in a capillary tube C 
of i mm. internal diameter, 6 mm. external diameter, and about 
3 cm. long. Over this a short piece of soft rubber tubing, 
3 mm. internal diameter, and 6.5 mm. external diameter, is 
wired on. The rubber tube is closed by a Mohr pinchcock E 
which is put on close to the end of the capillary. Originally 
the burette terminated in a glass stopcock, but this renders 
the apparatus fragile and costly. If the apparatus is properly 
manipulated during the analysis the rubber tube does not come 
in contact with more than traces of the absorbent and will re- 
main in good condition for a considerable length of time. It 
should, however, be tested from time to time to see that it is 
tight. The pinchcock should always be taken off from the 

1 The Hempel apparatus for technical gas analysis is excellently constructed by 
Greiner and Friedrichs of Stiitzerbach in Thiiringen, Germany. 

51 



GAS ANALYSIS 



rubber tube after using as this helps much to keep the latter 
in good condition. Notwithstanding the fact that readings 
cannot be made under the rubber tube, no measurable error re- 



B 






FIG. 33 



GAS ANALYSIS OVER WATER 53 

suits therefrom, since the internal diameter of the glass tube C 
is very small. The differences in volume are much less than a 
tenth of a cubic centimeter, a variation which, in determina- 
tions not made over mercury, may be entirely disregarded. The 
graduated measuring tube A contains 100 cc., the lowest mark 
being slightly above the iron foot. The cubic centimeters are 
divided into fifths, and the numbers run both up and down. 
The level-tube B is somewhat widened at the upper end to 
facilitate the pouring in of the confining liquid. 

In the Hempel method of gas analysis the absorbable constit- 
uents of a gas mixture are successively removed by passing 
the gas into a series of gas pipettes containing suitable reagents. 
The construction of these pipettes is such as to render it possible 
to bring the gases into intimate contact with the absorbents. 
The pipette may even be disconnected from the burette and 
vigorously shaken. There must be at least as many pipettes as 
there are absorbable constituents in the gas mixture. 

The following forms, varied to suit the nature of the different 
reagents, are used: 

THE HEMPEL SIMPLE ABSORPTION PIPETTES 

These are modifications of the Ettling gas pipette, first used 
by Doyere for the absorption of gases, and they are filled with 
such absorbing liquids as are not affected by the air. 

The Hempel Simple Absorption Pipette for Liquid Reagents 

It consists of two large bulbs, a and b (Fig. 34), joined by the 
tube d, and of a capillary glass tube c of i mm. internal diameter, 
and 6 mm. external diameter and bent as shown in the figure. 
The distance h must be greater than g to render it possible to 
inclose a gas between two columns of liquid in the pipette. 

The bulb a holds about 100 cc., and b about 150 cc., so that 
when 100 cc. of gas is brought into b, sufficient space for the 
absorbing liquid will remain. To protect the pipette from 



54 



GAS ANALYSIS 



being broken and to facilitate its manipulation, it is fastened 
to a wooden or iron stand. 

An iron stand is preferable to wood because its greater weight 
renders it more stable and because it cannot warp out of shape. 
An iron stand with a four-sided base is superior to one with legs 
only at the ends because with the latter form of base there is 
danger that one leg of the pipette may be pushed over the 

edge of the stand (see 
Fig. 38) and the appara- 
tus fall and be broken. 

The pipette is fastened 
in the iron standard at the 
three points shown in Fig. 
34. The capillary tube 
and the tube above a are 
slipped through openings 
in the upper bar of the 
frame and the tube below 
b is set back against the 
lower cross-bar. The small 
plate that closes this lower 
opening is then fastened 
in place by screws, and 
the spaces between the 
three tubes and their iron 



& 




FIG. 34 



collars are filled with Plaster of Paris. It is well to bring the 
Plaster of Paris up around the lower part of b for the purpose 
of giving the bulb additional support. If the pipette is broken, 
the plate is unscrewed, the glass parts and the Plaster of 
Paris are broken out and a new pipette is slipped into place 
and fastened as above described. With the style of mount- 
ing here recommended, the breakage of the Hempel pipettes is 
very slight, and the life of the apparatus is much greater than 
when the pipettes are mounted on light wooden frames, or are 
held in place by clamps and corks as some writers have advised. 



GAS ANALYSIS OVER WATER 



55 



The capillary tube should project from two to three cm. above 
the frame. A short piece of rubber tubing is wired on the 
free end of the capillary. 

The Hempel Simple Absorption Pipette for Solid and 
Liquid Reagents 

The only difference between this and the simple pipette is 
that in place of the bulb b there is inserted the cylindrical part 




FIG. 35 

A (Fig. 35), which can be filled with solid substances through 
the neck N. This neck is closed by a cork or rubber stopper 
which is held in place by a wire. 

A glass tube closed at the top, and over which a rubber ring, 
cut from a rubber tube, is drawn, also makes a good stopper. 
By this arrangement only a narrow strip of rubber is exposed 
to the action of the reagent. 



56 GAS ANALYSIS 

Pipettes of this form are used for the determination of oxygen 
by means of phosphorus (see p. 163). In such case it is neces- 
sary to protect the reagent from the action of the light when 
the pipette is not in use, which is done either by covering the 
pipette with a light box, or by making the cylinder A of brown 
glass. 1 

THE HEMPEL DOUBLE ABSORPTION PIPETTES 

Reagents that are acted upon by oxygen, i.e. alkaline pyro- 
gallol, cuprous chloride, ferrous salts, etc., cannot of course be 
kept in the above forms of pipette, since the reagent would 
become inactive in a short time through contact with the air. 
Hempel first sought to avoid this difficulty by protecting the 
reagent with a layer of high-boiling petroleum, after first con- 
vincing himself that the tension of the petroleum, resulting 
from its solubility in the reagent, did not cause a perceptible 
error. It was soon found, however, that although such hydro- 
carbons lessen decidedly the access of air, they do not by any 
means form a perfect protection. Further experiment on this 
subject led to the construction of 

The Hempel Double Absorption Pipette for 
Liquid Reagents (Fig. 36) 

This pipette permits the use of the reagents in question under 
an easily movable atmosphere that is free from oxygen, and 
the reagent may be kept completely saturated with those con- 
stituents of the gas that it does not strongly absorb, which is 
a great advantage. The pipette consists of the large glass bulb 
A, of about 150 cc. capacity, and three smaller bulbs, B, C, 
and Z>, each containing only 100 cc. They are connected by the 
bent tubes E, F and G, and end in the bent capillary tube K. 

The pipette is fastened to an iron stand in the manner already 
described (see p. 54). 

1 Fritz Friedrichs, /. Am. Chem. Soc., 34 (1912), 1513; Z. f. angew. Chem., 25 
(1912), 1905. 



GAS ANALYSIS OVER WATER 



57 



The pipette is prepared for use by slipping into the rubber 
tubing at S the tip of a burette containing the absorbing solution 
and allowing this to flow into the bulb A through the capillary 
K. The flow of the liquid through K may be hastened by ap- 
plying gentle suction with the mouth upon a rubber tube at- 
tached to M. When the contents of the burette has been drawn 
into A, air is blown by the mouth through the rubber tubing 
attached to M. The r-, 

air in A is forced out x* - r\ 

through the capillary 
and the burette until 
the liquid in B falls to 
the point E. The stop- 
cock of the burette is 
then closed, the burette 
is again filled with the 
absorbent and the op- 
eration is repeated un- 
til the bulb A and the 
tube E are full. If the 
operation has properly 
been performed the ab- 
sorbing liquid should 
fill the capillary K, the 
bulb A, and the con- 
necting tube E up to the bulb B, and B should be empty. The 
burette is now disconnected from S, and suction is applied 
at M until the absorbent is drawn up to the top of the bulb B, 
if the reagent does not absorb oxygen. 5 is then closed with 
a pinchcock, and water is poured into M until the bulb D 
is full. Upon opening S and gently blowing into M water will 
rise in C and the reagent in A , and if the filling has properly been 
performed the reagent will stand at the top of the capillary K 
when the water in the bulb C reaches to the top of that bulb. 

If the reagent absorbs oxygen the solution should, after A 




FIG. 36 



5 8 GAS ANALYSIS 

has been filled with it, be drawn up in B before the introduction 
of the water only to about two-thirds of the height of B, and 
the bulb D filled with water in the manner already described. 
Upon the absorption of the oxygen from the air by the reagent in 
the bulb C there will remain between the liquids in the bulbs 
B and C the desired volume of gas, about 100 cc. 



The Hempel Double Absorption Pipette for Solid and 
Liquid Reagents (Fig. 37) 

The construction may easily be understood from the figure. 
To prepare this double pipette for use, turn it upside down, in- 
troduce through the neck N of the bulb A the solid substance 
to be employed, close the 
neck with the stopper, and 
wire the stopper in place. 
Bring the pipette into an 
upright position and fill it 
with liquid in the manner 
described above. 

While the reagent in the 
simple pipette may be con- 
sidered to be saturated with 
gas only when it is kept in 
continual use, that in the 
double pipette, on the con- 
trary, remains saturated for 
an exceptionally long time, 
since the diffusion must 
take place through the con- 
fining 100 cc. of water and through the narrow tube that con- 
nects the bulbs C and D. The error caused by this theoretical 
possibility may be wholly disregarded in using the pipette. 

When the pipettes are not in use the rubber tubing on the 
capillary should be closed by the insertion of a short piece of 




FIG. 37 



GAS ANALYSIS OVER WATER 59 

glass rod. A pinchcock should not be left on this rubber tubing, 
since it causes rapid deterioration of the rubber. The open end 
of the single pipettes may be closed by the insertion of a small 
cork. 

MANIPULATION OF THE HEMPEL APPARATUS 

If the burette has been in use clean it thoroughly, and rinse 
it well with water. Examine the rubber tubing attached to 
the capillary of the burette to see that it is intact and that the 
wire ligature is in good condition. Make sure that the pinch- 
cock closes the rubber tubing completely. Open the pinchcock 
E, Fig. 38, and slip it down over the capillary tube. Pour into 
the open end of B water that has been saturated with the gas 
mixture that is to be analyzed until A and B are rather more 
than half full. 

Saturation of Confining Water. A simple method of satu- 
rating the water with the gas is to place the water in a washing 
flask and run the gas through the flask until the air has been 
displaced, and to then close the exit tube and shake the con- 
tents of the flask vigorously. 

Filling Burette with Confining Liquid. Drive out all air 
from the large rubber tubing connecting A and B by raising 
and lowering the tubes alternately, keeping the rubber tubing 
taut during this operation. Grasp the iron base D in the left 
hand and raise it until the water begins to flow out of the top 
of the burette. Then close the rubber tube of the burette with 
the pinchcock, setting the pinchcock up close to the end of the 
capillary. Compress the rubber tubing at D between the thumb 
and fingers of the left hand and pour out the excess of water 
that is in B. 

Measurement of 100 cc. To measure off exactly 100 cc. of 
the gas sample, insert into the rubber tube at the top of the 
burette a capillary tube connected with the gasometer or pipe 
from which the sample is to be taken, after first displacing the 
air in this connecting capillary by the gas to be examined. 



6o 



GAS ANALYSIS 



M 




FIG. 38 

Grasp the upper part of the level-tube B in the left hand. Lower 
it below A and open the pinchcock E with the right hand. 
Draw somewhat more than 100 cc. of gas into the burette. Close 



GAS ANALYSIS OVER WATER 6 1 

the pinchcock E, place the level- tube on the table and allow the 
water in the burette to run down for one minute. 1 Disconnect 
the capillary tube from the gasometer, raise the level-tube with 
the right hand until the gas in the burette is compressed to a 
volume less than 100 cc. and then close the rubber tubing at G 
tightly by squeezing it close up to the lower end of the burette 
between the thumb and first finger of the left hand. Place the 
level-tube on the table, grasp the iron base of the burette with 
the right hand and keeping the rubber tubing at G still tightly 
compressed raise the burette until the meniscus of the water 
in it is on a level with the eye. Then gradually release the pres- 
sure on the rubber tubing until the water in the burette falls 
exactly to the 100 cc. mark. Keeping the tubing still compressed, 
place the burette on the table and open the stopcock E for a 
moment to permit the excess of gas to escape. The burette 
should now contain 100 cc. of the gas under atmospheric pres- 
sure. To ascertain whether this is the case, grasp the base of 
the burette in the right hand and of the level-tube in the left 
hand and holding the burette perpendicularly lay the level- 
tube at an angle across it, and bring the water in the two tubes 
to the same level. If the measurement of the sample has prop- 
erly been made the water in the burette will stand exactly at 
the 100 cc. mark. 

Absorption of a Gas. To remove an absorbable constit- 
uent of the gas the burette and proper absorption pipette are 
connected in the manner shown in Fig. 38. Place the burette 
and level-tube on the table, the level-tube B at the left, bring 
up near the side of the burette the wooden stand S, and place 
on the stand a pipette containing the proper absorbent. Insert 
in H the bent glass capillary tube F. These connecting capillary 
tubes are of the same dimensions as the capillary tubes of the 
burette and pipette, namely, 6 mm. external diameter and one 
mm. bore. The horizontal portion is about 6 cm. 'long and the 
legs each about 2.5 cm. long. Slip a piece of rubber tubing about 

1 See p. 68. 



62 GAS ANALYSIS 

30 cm. long over the tube M of the pipette. Grasp F between the 
thumb and fingers of the right hand, squeeze the rubber tube E 
on the capillary of the burette between the thumb and fingers 
of the left hand, blow gently through M until the liquid in the 
pipette is driven to the farther end of the connecting capillary 
tube F and then insert the end of F into the rubber tube on the 
burette. If the connection is properly made there will be prac- 
tically no movement of the reagent in the connecting capillary 
tube. 

Even if a linear centimeter of air should appear in the capil- 
lary, the error arising therefrom may be disregarded, since 
capillary tubing with a bore of about one mm. contains only 
about .01 cc. in one linear cm. If, however, after F has been 
inserted in E, more than a linear centimeter of air appears in F, 
it shows that the connection was carelessly made, and F should 
be slipped out of E and the operation repeated. 

Certain reagents should never be allowed to come into con- 
tact with the rubber tube at H. In such case the liquid is forced 
upward in the capillary of the pipette until it stands just below 
the iron of the frame. If quite accurate results are desired, al- 
lowance should be made for the very small amount of air thus 
left in the connecting capillary tubes. This may easily be done 
by measuring the length of the capillary tube that is empty of 
liquid. Every ten centimeters of length corresponds to o.i cc. 
of air. This correction is not necessary in ordinary technical 
analysis. 

When the pipette and burette have been connected in the 
manner above described the pinchcock on E is opened, the 
level- tube B is slowly raised and the gas is driven over into the 
pipette. Water is allowed to flow into the capillary F until 
it reaches the point in the bend of that tube to which the reagent 
had been driven over. The pinchcock at E is then closed. This 
manipulation leaves the capillary tube of the pipette and the 
greater part of the bent connecting capillary tube filled with 
the gas mixture under examination together with such portion 



GAS ANALYSIS OVER WATER 63 

of the reagent as adheres to the walls of these capillary tubes. 
This adhering reagent suffices to remove the greater part of 
the absorbable constituent in the gas mixture because a slender 
column of the gas stands in contact with a comparatively large 
surface of the reagent, but even if the absorbable constituent 
should constitute 40 per cent of the gas mixture, and only half 
of this gas in the capillary tubes should be absorbed by the re- 
agent on the walls, the error thus caused would be negligible 
in technical analysis. This is apparent when we consider that 
the total length of the two capillary tubes is about 40 cm. and 
that the volume of gas in these tubes is, consequently, about 
0.4 cc. The volume of the absorbable constituent would then 
amount to 0.16 cc. and if only half of this were absorbed the 
error would be 0.08 cc. These figures illustrate an extreme case. 
If the absorbable constituent amounted to not more than 20 per 
cent of the gas mixture and if, as may usually be expected, 
80 per cent of it were absorbed, the error due to incomplete 
removal of this constituent in the capillary tubes would be less 
than 0.02 cc. After the constituent that is to be removed has 
been entirely absorbed, the gas is drawn back into the burette. 
This is done by grasping the level-tube with the left hand and 
bringing it into such position that the confining liquid in it 
stands slightly lower than that in the burette. The pinchcock 
E is opened, the level-tube is slowly lowered and the gas is 
drawn back into the burette until the liquid from the pipette 
reaches the same point in F at which it originally stood. The 
pinchcock E is now closed, the water in the burette is allowed 
to run down for one minute, and the gas volume in the burette 
is then read in the manner above described. 

It frequently happens that complete absorption of the gas 
can be accomplished only by shaking the pipette after the gas 
has been driven over into it. In such case a second pinchcock 
is placed on the rubber tube H, and after the gas has been trans- 
ferred to the pipette, both E and H are closed. The frame of 
the pipette is now grasped in the right hand, the burette is 



64 GAS ANALYSIS 

steadied with the left hand, and the absorbent is brought into 
intimate contact with the gas by gently rocking the stand back- 
ward and forward on the front edge of its base. 

If the reagent has no appreciable effect upon rubber, much 
time may be saved in making the connection between pipette 
and burette by preparing the pipette in such manner that it 
will stand ready at all times for connection with the gas burette. 
This is done by placing a pinchcock upon the rubber tube of the 
pipette, inserting into this tube the bent connecting capillary 
tube, and then, holding the pinchcock open, driving the reagent 
over nearly to the further bend of this connecting capillary by 
blowing into the large rubber tube attached to M. The pinch- 
cock is then closed. If the operation has been correctly per- 
formed, the reagent should now stand close to the bend in the 
connecting capillary tube that is nearest the burette. The 
capillary tube is next inserted in the rubber tube of the burette 
and the absorption is made in the manner above described. 
After the absorption of the gas, the reagent is drawn over nearly 
to the further bend of the connecting capillary tube, and the 
pinchcock on the pipette is then closed. This should drive the 
reagent to about the same point in the connecting capillary 
as that at which it first stood. The capillary tube is now with- 
drawn from the rubber tube that is attached to the top of the 
burette, and the pipette is removed. The pipette, with the bent 
capillary tube attached to it, now stands filled with the reagent 
to the further bend of the connecting capillary and is ready for 
immediate connection with the burette when another determina- 
tion of the same constituent gas is to be made. 

The manipulation of the pipettes filled with solid absorbents 
is still simpler, for in this case no shaking is necessary because 
of the large surface of contact between the solid and the gas. 
On this account also the apparatus need not be disconnected. 

The Hempel apparatus for technical gas analysis possesses 
many points of superiority over other forms of apparatus. It 
is not fragile and if a part is broken it is easily replaced. It 



GAS ANALYSIS OVER WATER 65 

contains no stopcocks. It is easily cleaned. Either water or 
mercury may be used as the confining liquid. When water is 
employed, it is easily saturated with the gas mixture under analy- 
sis. The pipettes avoid waste of reagent and protect the reagents 
from the air. The removal of absorbable constituents of a gas 
mixture may rapidly and completely be effected. 

Absorbing Power of a Reagent. If the absorbing power 
of the reagent is known, waste may be avoided, and with one 
filling of the pipette several hundred analyses (the number 
depending upon the nature of the gases examined) may be 
made, with certainty throughout as to the efficiency of the ab- 
sorbent. 

To determine the absorbing power of a reagent, Hempel 
uses a pipette of the form shown in Fig. 39. The pipette is 
filled with mercury, and then one cc. of the solution of the re- 
agent is drawn in through the capillary d. Mercury is allowed 
to follow the solution so that the reagent is inclosed between 
the mercury in the pipette and the mercury standing in the 
capillary. The pipette is connected by means of rubber tubing 
and a bent capillary tube with a Hempel burette containing 
the gas under consideration. The gas is drawn into the pipette 
and shaken with the reagent as long as rapid absorption takes 
place. It is then passed back into the burette and measured. 
The absorbing power of the reagent thus experimentally de- 
termined is much higher than could safely be relied upon in 
actual gas analysis, and consequently under the assumption that 
only a fourth of the active reagent should be used up if there 
is to be no doubt as to its absorbing power, the result in each 
case is divided by four and the figure thus obtained is termed 
the analytical absorbing power of the reagent. This figure, of 
course, refers to the absorbing power of one cc. of the reagent. 
To illustrate, one cc. of a 33 per cent solution of potassium 
hydroxide was found to absorb readily 160 cc. of carbon dioxide. 
The analytical absorbing power of a solution of potassium 
hydroxide of the above strength is consequently stated to be 



66 



GAS ANALYSIS 



40, which means that one cc. of the reagent may be relied upon 
to absorb 40 cc. of carbon dioxide in gas analytic work. 

If an accurate account is kept of the amount of gas that the 

i 




FIG. 39 

reagent in a pipette has absorbed, the efficiency of the reagent 
still remaining in a pipette is always known, and the absorbent 
can be used to the full extent of its analytical absorbing power 
without uncertainty as to the accuracy of the analysis. 



GAS ANALYSIS OVER WATER 67 

Accuracy of Analyses with the Hempel Apparatus. The 

criticism has been urged against the Hempel apparatus that it 
is cumbersome, and that as a consequence rapid analytical work 
cannot be performed with it. Those who are familiar with the 
manipulation of the various standard forms of apparatus for 
technical gas analysis will, however, probably concur in the 
statement that an analysis of any of the usual gas mixtures 
can be performed with the Hempel apparatus with as great 
or even greater speed than that attainable with almost any other 
device, and with an accuracy far surpassing that of most other 
technical methods and approximating that obtained over mer- 
cury. This is shown by two partial analyses of illuminating 
gas: 

I. Technical II. Technical Exact Analysis over 

Analysis Analysis Mercury 

i . 6 per cent i . 5 per cent i . 5 per cent carbon dioxide 

3.1 " 2.9 " 3.0 " heavy hydrocarbons 

1.4 " 1.6 " 1.4 " oxygen 

It should be borne in mind, however, that with the Hempel 
apparatus for technical gas analysis, as with any other form of 
apparatus, errors so large that they may entirely destroy the 
value of the analysis will result when the reagents and the 
confining water do not have the temperature of the laboratory 
or when there is appreciable change in temperature during the 
brief time necessary for the analysis. A rise of temperature 
of only one degree would cause an error of 0.3 % in a total 
volume of 100 cc., which makes it evident that the analysis 
should be made in a laboratory that is of nearly constant tem- 
perature, or, if the work must be done outside of the laboratory 
under fluctuating temperature, the burette should be surrounded 
with a water jacket. The jacketing of the Hempel burette may 
easily be effected by slipping down over the burette an inverted 
single bore rubber stopper about 4 cm. in diameter, and slip- 
ping over the burette and upon the stopper a large glass tube 
somewhat shorter than the burette, holding the upper end in 



68 GAS ANALYSIS 

place by means of a split cork. The larger tube is then filled 
with water. 

Running Down of Confining Liquid. It is also of import- 
ance, if accurate results are desired, that the confining liquid 
over which the gas is measured be allowed to flow down the 
walls of the burette in exactly the same manner and for the 
same length of time after each absorption. If the tube of the 
Hempel burette is clean, the running down of water is practically 
complete in three minutes. If the burette is allowed to stand 
two minutes longer and the water given five minutes in all 
to run down, the meniscus will stand from .02 to .03 cc. 
higher than after three minutes, a difference that is negligible in 
technical gas analysis with water as the confining liquid. In 
the description of the manipulation of the apparatus on page 61 
it was stated that the water should be allowed to run down for 
one minute. The results will naturally be more accurate if the 
three minute interval is employed, but for technical analyses 
where speed is a desideratum and great accuracy is not neces- 
sary, much time may be saved by making the readings only 
one minute after the gas has been passed back into the burette. 
The following analyses made by Dr. R. P. Anderson in the 
Cornell Laboratory show the variation in the results when the 
water in the burette is allowed to run down one, two, three and 
five minutes. 

Determination of Oxygen with the Phosphorus Pipette 
August 8, 1911 

i Minute 2 Minutes 3 Minutes 5 Minutes 

I 20 . 6 20 . 7 20 . 8 20 . 8 

II 20 . 6 20 . 7 20 . 8 20 . 8 

III 20.6 20.7 20.8 20.8 

In apparatus in which gas volumes are read over liquids other 
than water or mercury, such as solutions of fixed alkalies, 
cuprous chloride, alkaline pyrogallol, and the like, the running 
down of the liquid takes place slowly, and an error in measure- 



GAS ANALYSIS OVER WATER 



69 



merit of one cubic centimeter or more may result if the reading 
is not made under exactly the same conditions in all cases. 
While distilled water will run down completely in a Hempel 
burette in five minutes, a five per cent solution of sodium hy- 
droxide requires ten minutes and concentrated sulphuric acid 




FIG. 40 

from fifteen to twenty minutes. If in an analysis of a gas 
mixture the residual gas volumes are read first over one liquid 
and then over another, it is apparent that rapid and at the same 
time accurate work is almost if not quite impossible. 

Portable Hempel Apparatus. It must be conceded that the 
Hempel apparatus is not easy to carry about, but for the analysis 



yd GAS ANALYSIS 

of rather simple gas mixtures this objection is obviated by the 
portable Hempel apparatus devised by the present writer and 
shown in Fig. 40. The burette A has a capacity of 50 cc. and 
is calibrated in one-fifth cc. It is set in a square iron base that 
is grooved on two sides and slips over the wooden guides shown 
in the drawing. The level-tube B is similarly mounted and 
lies on the bottom of the case opposite the burette. The case 
contains three Hempel gas pipettes, one, E, a simple pi- 
pette for solid reagents, and two, C and D, double pipettes 
for liquid reagents. These pipettes are mounted on wooden 
frames to lessen the weight of the apparatus. The ap- 
paratus may be obtained with pipettes of different forms than 
those here given if the analyst should so desire. The 
drawer F contains small accessories such as rubber tubing 
for connections, and the bent capillary tubes for joining the 
burette with the pipettes. The front and the back of the case 
are fitted with sliding covers, and the top is provided with a 
metal handle. The apparatus is quite compact, the dimensions 
of the outer case being 20.5 cm. long, n cm. high, and 8 cm. 
wide. The total weight of the apparatus when the pipettes 
are not filled is 6.8 kilograms. 

It was formerly necessary to analyze gas mixtures containing 
carbon dioxide at the place where the sample is taken, because 
of the difficulty of obtaining a proper average sample of a gas 
mixture containing this ingredient and of transporting it to the 
laboratory without change in its composition. The Huntly 
sample tube described on p. 5 appears to remove this diffi- 
culty. 

THE MODIFIED WINKLER GAS BURETTE (Fig. 41) 

This gas burette is of use in the determination, directly in 
the burette, of gases that are readily soluble in water, such as 
ammonia or hydrogen chloride. Yet when a gas mixture con- 
tains gases that are easily soluble in water, it is generally 
preferable to pass a large volume of the gas mixture through a 



GAS ANALYSIS OVER WATER 



suitable absorbent, and to then 
determine the absorbed gas by 
titration. 

The Winkler burette consists 
of the level-tube a and the 
measuring tube b connected by 
a rubber tube about 120 cm. 
long and fastened into iron feet. 
b is a glass tube of about 100 cc. 
capacity, provided with the 
three-way cock c and the sim- 
ple glass stopcock d. The space 
between the two stopcocks is 
divided into exactly 100 equal 
parts, and each part into fifths. 
The capillary e has the same di- 
mensions as that on the Hempel 
burette. Instead of the glass 
stopcock d a rubber tube and 
pinchcock may be used as with 
the simple burette. 

Manipulation of the Wink- 
ler Burette. Before filling the 
burette with the easily soluble 
gases, the tube b is first dried by 
rinsing it out with a few cubic 
centimeters of absolute alcohol 
and then with ether, the latter 
being driven out by aspirating 
through the tube the gas to be 
analyzed. To do this, join the 
end e of the burette by means 
of a rubber tube, or better a 
glass tube, to the vessel contain- 
ing the gas and bring the three- 




FIG. 41 



72 GAS ANALYSIS 

way cock into such a position that its longitudinal opening 
communicates with the inside of the burette. Connect the cock 
with the aspirator. After the gas has been drawn through for 
a time, close the upper stopcock and turn the lower stopcock 
through an angle of 180. Place upon the tail of the lower 
(three-way) stopcock a short piece of rubber tubing and close 
this with a pinchcock. The gas, if under pressure, is brought 
to atmospheric pressure by momentarily opening the upper 
stopcock. The remainder of the apparatus is now filled with 
water run in through the three-way cock, which is so turned 
that it communicates with the rubber tube. The water must 
previously be saturated with those constituents of the gas 
mixture which are slightly soluble in water. The easily soluble 
gas in the mixture is then absorbed by turning c into such 
position that a and b are connecting, allowing some water 
from a to rise in , closing c and, with b held in a horizontal 
position, running water backward and forward to promote 
the absorption of the gas. b is then placed in an upright 
position, c is opened and the residual gas volume is read. 
c is then closed and the gas in b is shaken again with the 
water, and after opening c the volume is again read. This is 
continued until no further diminution of the gas volume in b 
takes place. The constituents that are only slightly soluble 
in water are determined by absorption in the Hempel pipette 
in the usual manner. 

THE HONIGMANN GAS BURETTE 

The Honigmann gas burette is suited only to the rapid and 
approximate determination of carbon dioxide in gas mixtures 
that contain fairly high percentages of this constituent. 

The burette A (Fig. 42) contains 100 cc. divided into f cc., 
the zero point being at the lower end of the burette. At the 
top it is closed by a glass stopcock and the lower end below 
the graduation is drawn out to smaller diameter to permit 
of a piece of rubber tubing being easily slipped over it. The 



GAS ANALYSIS OVER WATER 



73 



absorbing liquid, potassium hydroxide, is placed in a glass cylin- 
der c, which should be tall enough to allow the burette to be 
lowered to any desired point into the liquid. 
Manipulation of the Honigmann 
Burette. In making a determination, 
the burette is first thoroughly cleaned 
with water, and the gas to be analyzed is 
then passed through it until all air in the 
burette has been displaced. Stopcock a 
is now closed and the rubber tube is im- 
mersed in a solution of potassium hy- 
droxide in the manner shown in the fig- 
ure. The solution of potassium hydroxide 
contains one part of commercial potas- 
sium hydroxide dissolved in two parts of 
w r ater. The burette is lowered into this 
solution until the liquid stands exactly at 
the zero point. The stopcock a is then 
carefully opened until the liquid inside the 
burette rises to the same mark, and it is 
then closed. The tube now contains 100 
cc. of the gas at atmospheric pressure. 
The absorption of the carbon dioxide is 
effected by grasping the burette between 
the thumb and fingers in the manner 
shown in the figure, and turning it down- 
ward so that the caustic potash will flow 
along the walls of the burette. During 
this operation the open end of the rubber 
tube must, of course, remain below the 
surface of the solution in the cylinder. 
After all the carbon dioxide has been absorbed, the burette is 
again brought to a perpendicular position and is lowered into the 
liquid in the cylinder until the liquid surfaces on the inside and 
outside of the burette stand at the same height. The reading 




FIG. 42 



74 GAS ANALYSIS 

is now taken, and the result gives directly the percentage amount 
of carbon dioxide present in the original gas mixture. 



THE BUNTE GAS BURETTE 

The Bunte burette may be used for the approximate determi- 
nation of carbon dioxide and oxygen. 

The burette A (Fig. 43) is closed at the top by the three-way 
stopcock C, and above this there is the tube Z>, which is pro- 
vided with a mark about 5 cm. above the stopcock. The lower 
end of the burette is closed by a simple glass stopcock, and is 
connected with the level-bottle B by a long piece of rubber 
tubing. A pinchcock is placed upon this rubber tube a short 
distance below the end of the burette. Inasmuch as all of the 
readings with this burette will probably lie between the zero 
point and the 50 cc. mark, the instrument is made shorter, and 
consequently easier to handle, by widening the upper portion. 
The horizontal opening of the stopcock C is closed by a piece of 
rubber tubing and a pinchcock. The burette and level-bottle 
are supported on an iron stand of the form shown in the figure, 
the burette being held in a spring clamp which permits of its 
easy removal. The calibration of the burette runs from the 
zero point, which is near the lower end, up to 100 cc. at the 
upper stopcock. The calibration is carried on below the zero 
point for 10 cc. There must also be provided a thick walled 
glass bottle 5* supplied with a one-hole rubber stopper carrying 
a short piece of glass tubing which is closed by a piece of rubber 
tubing and a screw pinchcock. A piece of glass tubing bent 
in the shape is also necessary for running water into D. 

Manipulation of the Bunte Burette. Fill the level-bottle 
B with water, connect the rubber tube with the burette in 
the manner shown in the figure, open the pinchcock H and 
the two stopcocks of the burette, and allow water to rise 
in the burette until D is partially filled. Close G and H. Now 
turn the stopcock C until D communicates with F, and open 



GAS ANALYSIS OVER WATER 



75 



the pinchcock on F until the bore of the stopcock and the rub- 
ber tube are filled with water. Then close the pinchcock. Slip 
the pinchcock H up to the lower end of the burette. Close it, 
and remove the long rub- 
ber tube from the bu- D 

rette. Place under the 
burette a beaker to catch 
the water which runs out. 
Connect F with the res- 
ervoir containing the 
gas to be analyzed, and 
open the pinchcock on F 
and the lower glass stop- 
cock of the burette. The 
water in the burette will 
now flow out, and the gas 
will be drawn over into 
the tube. Draw into the 
burette rather more than 
100 cc. of gas. 

The gas in the burette 
is always read at the 
pressure of the atmos- 
phere plus the pressure 
of the column of water 
standing in D up to the 
mark. For convenience 
in calculating results it 
is desirable that the orig- 
inal volume be exactly 
100 cc. at this pressure. 
To measure off this exact 
volume close the stop- 
cock C, open the pinch- 
cock H until the long 




FIG. 43 



76 GAS ANALYSIS 

rubber tube is filled with water, and then slip this carefully 
over the lower end of the burette, after first making sure 
that there are no bubbles of gas in the tip of the burette 
below the stopcock. Now open H and G, and allow water to 
rise nearly to the zero point. Close G, and then turn C, so that 
A communicates with D. Since the gas in the burette is under 
slight pressure, bubbles will escape upward through the water in 
D. Bring the water in D exactly to the mark, and then by 
carefully opening G allow the water in the burette to rise 
until it stands exactly at zero. There is now in the burette 
100 cc. of gas under the pressure of the atmosphere plus 
the column of water in D. Close C, and proceed to the ab- 
sorption of the constituent of the gas mixture that is to be 
determined. 

This absorption is brought about by introducing a liquid ab- 
sorbent into the burette through the lower end. Since these 
absorbents for the various gases are usually concentrated solu- 
tions, it is undesirable to allow the absorbent to be diluted by 
the water still remaining in the burette between G and the 
zero point. This water is therefore first removed with aid of 
the suction bottle S. This bottle is connected by means of the 
rubber 'tube at its top with a water suction pump, and is ex- 
hausted of air. The screw pinchcock is then closed, the long 
rubber tube is slipped off from the lower end of the burette, 
and the rubber tube of S is slipped over the burette tip. The 
screw pinchcock on S is now opened, G is then carefully turned, 
and the water in the burette is slowly drawn off until it has 
fallen to a point just above G. G is then closed, the pinchcock 
of 5 is closed, and the suction bottle is detached. This operation 
serves also to bring the pressure of the gas in the burette below 
that of the atmosphere, and thus renders it possible to intro- 
duce the reagent through the lower end of the burette. The re- 
agent to be introduced into the burette is now poured into a 
small evaporating dish, and this dish is brought up under the tip 
of the burette; G is carefully opened, and the liquid at once rises 



GAS ANALYSIS OVER WATER 77 

in the burette. When no more will enter, close G, remove the 
dish, grasp the burette with the thumb and the first two fingers 
of the left hand at the stopcock C, and open the spring clamp 
with the right hand. Place the first and second fingers of the 
right hand below the stopcock G, pour out the water in Z>, and 
tip the burette backwards and forwards so that the absorbing 
liquid will flow along its entire length. Place it again in the 
clamp, bring the dish of the absorbent under the tip, and allow 
more liquid to enter if it will, repeating the tilting of the burette 
in the manner just described. When the absorbent will rise 
no farther in the burette, that is, when the absorption of the 
gas is completed, place the burette in the clamp in such a posi- 
tion that its upper end is below the level-bottle B, put a beaker 
under G, and insert in the end of the rubber tube of B the 
fl -shaped glass tube already mentioned. Hook this tube over 
the edge of D. Open the pinchcock H so that water will flow into 
D, then open C, and lastly open G. Water will now flow through 
the burette and wash out the absorbent, and yet no gas will 
escape during the operation. When the absorbent has been 
removed in this manner, close G, shut off the supply of water 
from B, and then carefully open G until the water in D falls 
just to the mark. Read the volume of gas now 'remaining in 
the burette. The difference between this volume and the origi- 
nal volume of 100 cc. will give the per cent of gas which has 
been absorbed. The same procedure is followed in the determi- 
nation of a second constituent in the same sample. 

Throughout the entire operation be sure not to touch with 
the hand any part of the burette except the two stopcocks, 
since otherwise the heat of the hand would expand the gas in 
the burette and cause some of it to escape through the open 
stopcock C. 

Determinations with the Bunte burette cannot be accurate, 
since the gas in the burette is brought into contact with large 
volumes of water that is unsaturated with the gas mixture, 
and which will therefore absorb some of the gas of the sam- 



78 GAS ANALYSIS 

pie. 1 The method is also wasteful of reagent, since the reagent 
which has once been employed cannot be used over again be- 
cause of its dilution by the wash water. 

THE ORSAT APPARATUS 

In the analysis of commercial grades of sodium carbonate 
there early arose a demand for a rapid and convenient method 
for the determination of carbon dioxide, which was met in 1868 
by the apparatus designed by Schlosing and Rolland. 2 In 1874 
Orsat patented a device 3 that was based directly upon the 
principle of the apparatus of Schlosing and Rolland, and that 
attracted considerable attention at the time and rapidly came 
into general use. Because of its compactness and ease of manip- 
ulation the Orsat apparatus has been and still is very generally 
employed by gas analysts. In its original form, however, and 
even in some of the later modifications it possesses certain 
inherent faults, and the unsatisfactory character of the analyti- 
cal results that are obtainable with the various forms is evi- 
denced by the large number of changes in its construction 
that are constantly being brought forward in chemical journals. 
The chief objection to the apparatus is the incompleteness of 
the absorption of such gases as oxygen and carbon monoxide. 
The researches of Gautier and Clausmann, Bendemann, Hankus, 
Hempel, Nowicki, Hahn, Dennis and Edgar and others have 
demonstrated that the complete removal of oxygen by alkaline 
pyrogallol and of carbon monoxide by cuprous chloride can be 
effected only when the absorbent and the gas are shaken to- 
gether, or when the gas is, in some manner, brought into pro- 
longed and intimate contact with the absorbent. With most 

1 The manner of manipulation of the Bunte burette described by Haber in the 
Journal fur Gasbeleuchtung, 39 (1896), 802, lessens the errors due to the absorption 
of the gases by the wash water, but is probably too inconvenient to be generally 
followed. If the burette is used in the customary manner, it does not give accurate 
results. 

2 Annales de chimie et de physique, 4 serie, 14 (1868), 55, 

3 Chem. News, 29 (1874), 177. 



GAS ANALYSIS OVER WATER 79 

of the suggested forms of the Orsat absorption pipette, the 
removal of oxygen and carbon monoxide is quite incomplete 
unless the gas is allowed to stand in contact with the absorbent 
for a very considerable length of time, or is passed back and 
forth many times between the burette and pipette. Failure to 
recognize this inadequacy of the apparatus frequently results 
in the incomplete removal of oxygen, and, as a consequence, a 
decrease in volume is observed when the gas mixture is next 
passed into the cuprous chloride pipette. In very many cases 
the analyst has in this manner been led into reporting carbon 
monoxide in a gas mixture, such as flue gas, when in fact no 
carbon monoxide is present, the decrease in volume being due 
solely to the absorption, by cuprous chloride, of oxygen that 
still remains in the gas mixture. 

In recent years several interesting and some valuable sug- 
gestions for increasing the completeness and rapidity of ab- 
sorption in the Orsat apparatus have appeared in chemical 
journals. Bendemann proposes * that two pipettes be used for 
the absorption of oxygen by alkaline pyrogallol and two for the 
removal of carbon monoxide by cuprous chloride. This would 
undoubtedly lessen the errors of the determinations but would 
hardly remove them entirely. More worthy of consideration 
are the proposed modifications of the form of the absorption 
pipette to bring gas and liquid into intimate contact. Most 
of these are based upon the construction described in 1899 by 
E. Hankus 2 and shown in Fig. 44. The gas enters the pipette 
through A, passes downward through the capillary and, by 
impinging on the plate , is broken up into minute bubbles 
which then pass upward through the absorbing liquid. The 
gas is brought back into the burette by turning the stopcock 
through an angle of 180 and lowering the level-bottle of the 
burette. 

In 1911 the Chemists' Committee of the United States Steel 

1 Jour.f. Gasbeleuchtung, 49 (1906), 853. 

2 0sterr. Chem. Ztg., 47 (1899), 81; /. Gasbeleuchtung, 49 (1906), 367. 



So 



GAS ANALYSIS 



Corporation described 1 an absorption pipette (Fig. 45) that 
is quite similar to the form proposed twelve years earlier by 
Hankus, but is slightly less efficient than the Hankus pipette 
(see results below) since it permits the gas to escape freely in 
large bubbles from the lower end of the capillary tube. 

The pipette devised by Nowicki 2 and improved by Heinz 3 
(Fig. 46) yields more complete absorption than that of Hankus. 

A 



\ 







FIG. 44 



FIG. 45 



FIG. 46 



The gas passes downward through the straight capillary tube A 
and then rises in small bubbles through the spiral tube 5 which 
insures long and thorough contact between the gas and absor- 
bent. A short tube D is attached to the lower end of the spiral, 
and fresh absorbing liquid is drawn upward through this open- 

1 Met. and Ghent. Eng., 9 (191 1), 303. 

2 Osterr. Zeit. f. Berg.-Hiitt., 53 (1905), 337. 

3 /. Gasbeletichtung, 49 (1906), 367. 



GAS ANALYSIS OVER WATER 



81 





ing when the gas bubbles rise through the spiral. Experience 
has shown, however, that when this form of absorption pipette 
is used for the determination of oxygen with alkaline pyrogallol 
the gas is frequently trapped in the spiral. Moreover, the 
pipette is so fragile that it is often broken in transportation, 
which renders it unsuitable for use in a portable apparatus. 

The very rapid and complete absorption of gases that upon 
experiment was found to be obtainable with the Friedrichs 
gas washing bottle 1 led the 
author to employ the same prin- 
ciple in the construction of an 
absorption pipette for the Orsat 
apparatus, the form of pipette 
that was finally adopted being 
that shown in Fig. 47. The 
gas mixture enters the pipette 
through the capillary A (the 
stopcock being in position I), 
and, passing downward through 
the capillary, escapes at B. 
It then rises and in so doing 
follows the spiral S. The rising 
gas carries some of the absorb- 
ing liquid with it, and this liquid 
then flows down on the inside of 
the cylinder C and mixes with 
the main body of the absorbent 
again at D. After the gas has 
risen through the spiral and has 

collected in the space F, the stopcock is turned through 180 
to position II and the gas is then drawn back into the burette. 

An experimental comparison of the different forms of Orsat 
pipette here illustrated has been made by Mr. F. H. Rhodes. 
In the first series of comparative determinations oxygen in 

1 Z. anal. Chem., 50 (1911), 175. 



s 



FIG. 47 



82 



GAS ANALYSIS 



atmospheric air was absorbed by means of an alkaline solution 
of pyrogallol. (See p. 160). One hundred cc. of air was measured 
off in a Hempel burette, and this was then connected with the 
pipette under examination, and the gas sample was passed back 
and forth between the absorption pipette and the burette until 
all of the oxygen in the sample had been absorbed. The air 
was passed into the several pipettes at a uniform speed. The 
absorption pipettes that were tested were 

(a) the usual form of Orsat pipette, which is filled with glass 
tubes to increase the absorbing surface; 

(b) the Hankus pipette (Fig. 44) ; 

(c) the absorption pipette recommended by the Chemists' 
Committee of the United States Steel Corporation (Fig. 45) ; 

(d) the Nowicki-Heinz spiral absorption pipette (Fig. 46) ; and 

(e) the new form of pipette here described (Fig. 47). 



TABLE I 

The sample of air was passed over into each absorption pi- 
pette in one minute. It was then immediately drawn back into 
the burette and again passed into the absorption pipette at 
the same speed as before. This was continued until all of the 
oxygen was absorbed. The results given in the tables are the 
averages of numerous determinations. 



Time 
(Minutes) 


(a) Orsat 
Usual 
Form 


(b) Hankus 
Pipette 


(c) U. S. 
Steel 
Committee 


(d) Nowicki- 
Heinz 
Pipette 


(e) Pipette 
New 
Form 


I 


8.0 


II . 2 


9.0 


20. 6 


18.6 


2 


13-3 


I6. S 


14.2 


20.8 


20.4 


3 


16.7 


19. 1 


17.2 


20.9 


20.9 


4 


18.7 


20. 1 


18.8 






5 


19-5 


20.5 


19.8 






6 


20.2 


20.7 


2O. 2 






7 


2O.4 


20.8 


20.6 






8 


20.8 


20.9 


2O.9 






9 


2O-9 











GAS ANALYSIS OVER WATER 



TABLE II 

In the analyses here tabulated, the sample of air was first 
passed into each pipette in two minutes, that is, at half the 
earlier speed. It was then immediately drawn back into the 
burette and passed a second time into the pipette in one 
minute. 



Time 
(Minutes) 


(a) Orsat 
Usual 
Form 


(b) Hankus 
Pipette 


(c) U. S. 
Steel 
Committee 


(d) Nowicki- 
Heinz 
Pipette 


(e) Pipette 
New 
Form 


2 


10.3 


15-6 


12.3 


20.7 


20. 6 


i minute more 


17.2 


18.3 


17.2 


20.Q 


20.Q 



The above results render it evident that the complete ab- 
sorption of oxygen from air can be effected with the first three 
forms of pipette only by repeated passage of the gas sample 
into the pipette and back into the burette. The Nowicki- 
Heinz pipette and the spiral pipette here proposed seem to be 
of nearly equal efficiency, but the former is open to the objec- 
tions already noted. 

To ascertain the efficiency of the new spiral pipette in the 
absorption of carbon monoxide, mixtures of this gas with known 
amounts of air were prepared; oxygen was determined in one 
spiral pipette by absorption with an alkaline solution of pyrogal- 
lol and carbon monoxide in a second spiral pipette by absorption 
with an ammoniacal solution of cuprous chloride. In the ab- 
sorption of oxygen the gas mixture was passed into the pipette 
in two minutes, was drawn back and then passed in a second 
time in one minute. In the absorption of carbon monoxide the 
same time intervals were found to give complete absorption 
of the gas unless the amount of carbon monoxide exceeded 
25 per cent. In such case it was found necessary to pass the 
gas mixture three times into the pipette, the first time in two 
minutes, and the second and third times in one minute each. 
The results were as follows: 



84 GAS ANALYSIS 



II in 



(Taken 17.7 16.2 13.2 

I Found 17.8 16.3 13.2 

., (Taken 15.8 22.9 37.3 

Carbonmonox.de ^ _ g 



It thus appears that with this form of absorption pipette 
both oxygen and carbon monoxide can be removed as com- 
pletely and as rapidly as is possible with the Hempel absorp- 
tion pipette in which the gas and absorbent are shaken together. 

A further error in analyses made with the usual forms of 
the Orsat apparatus results from the incorrect positions of 
the measuring burette. 1 After the removal of the absorbable 
constituents of the gas mixture the capillary tube that con- 
nects the burette with the pipettes remains filled with the com- 
bustible residue; consequently, when a portion of this residue 
is measured off in the burette and is passed to the combustion 
apparatus through the capillary tube above the pipettes, it 
will carry with it the combustible gas remaining in that capil- 
lary. This difficulty may be avoided by filling the connecting 
capillary with the confining liquid (water) in the manner sug- 
gested by Pfeifer, 2 or more simply by placing the burette be- 
tween the absorption pipettes and the combustion apparatus in 
the manner recommended by Hahn. 3 Since the Orsat apparatus 
is chiefly employed for the determination by absorption in liquid 
reagents of carbon dioxide, oxygen, and carbon monoxide, it 
is, in the opinion of the writer, preferable to limit the apparatus 
to the determination of these three gases and to construct it in 
such manner as to render it easily possible to connect the bur- 
ette, when so desired, with suitable special apparatus for the 
determination of hydrogen and hydrocarbons. The apparatus 

1 See Hahn, Zeit. d. Vereins deutscher Ingenieure, 1906; /. Gasbeleuchtung, 49 
(1906), 367. 

2 /./. Gasbeleuchtung, 51 (1908), 523. 
3 Loc. cit. 



GAS ANALYSIS OVER WATER 85 

is thus rendered smaller, more easily portable, and less fragile, 
and the combustion results, with proper apparatus, will usually 
be much more accurate than with the imperfect devices con- 
tained in the many forms of the Orsat apparatus now upon the 
market. 

A further drawback in the usual forms of Orsat apparatus 
is to be found in the rubber bulbs that are attached to the level- 
cylinders of the pipettes to protect the various reagents from 
the air. These bulbs rapidly deteriorate, and after short use 
fail to accomplish the purpose for which they are intended. 

In the hope of remedying some if not all of the defects of 
the Orsat apparatus that have been enumerated above, the 
author has designed the modification shown in Fig. 48.* 

The burette B has a capacity of somewhat more than 100 cc. 
and is graduated from a point near the bottom upward to the 
stopcock /. This stopcock is a three-way stopcock, the posi- 
tion of which is shown by means of a black glass H fused to 
its outer surface. The capillary tube connecting / with the 
pipettes and with the stopcock K has an external diameter of 
7 mm. and an internal diameter of one mm. In fusing on the 
branch capillaries that extend downward to the three pipettes, 
the internal diameter of the capillary should at no point be 
much greater than one mm. if the apparatus is properly made. 
The three absorption pipettes E, F, and G are of the form al- 
ready described, and are filled respectively with solutions of 
potassium hydroxide, alkaline pyrogallol, and ammoniacal 
cuprous chloride. They are connected with the capillary tube 
from the burette by means of pieces of soft, black rubber tubing 
of 1.5 mm. thickness of wall, and these rubber tubes are held 
in place by wire hooks that pass through the blocks behind the 
joints, and have threaded ends upon which small set screws are 
placed. This method of attachment renders it easily possible to 
remove all the glass parts from the frame. Into the open ends 

x The apparatus is manufactured by Greiner and Friedrichs, Stiitzerbach in 
Thiiringen, Germany. 



86 



GAS ANALYSIS 




FIG. 48 



GAS ANALYSIS OVER WATER 87 

of the three level-tubes of the pipettes are inserted one-hole 
rubber stoppers, and through the openings of these stoppers 
pass the branch tubes from the tube SS that is 7 mm. external 
diameter, and one mm. thickness of wall. This tube passes 
downward and is joined by a piece of rubber tubing to the upper 
side of the stopcock attached to the cylindrical vessel T which 
in turn is connected with V by the glass tube shown by the 
dotted line. After the pipettes have been filled with the several 
reagents, the stoppers connecting the level-tubes with the 
tube SS are inserted in place and the protecting reservoir VT 
is half filled with water. As the gas is driven over from the 
burette into the pipette and is drawn back into the burette, 
the water in VT rises and falls, but protects the reagents at 
all times from contact with the air. The level-bottle L is held 
in place by a clamp when the apparatus is in transport. 

Manipulation of the Orsat Apparatus. The level-bottle L 
is filled with water which is then driven up to the top of the 
burette B by turning the stopcock / to the position shown in 
the figure and raising L. The stoppers of the level-tubes of 
the pipettes E, F, and G are then removed and the solutions 
of the reagents that are to be used in the three pipettes are 
introduced into the level-tubes. The stopcock / is then turned 
so that the burette B is in communication with the capillary 
tube above the pipettes and the liquid in each pipette is drawn 
up almost to the lower side of the stopcock by turning the stop- 
cock to position II, Fig. 47, and lowering the level-bottle L. 
The stopcock of each pipette is closed when the absorbing liquid 
in it has been raised to this point. Water is now poured into 
the reservoir V until V and T are half filled. The stoppers 
attached to the branch tubes of the tube 55 are then inserted 
into the necks of the level-tubes of the pipettes. 

The stopcock J is now turned to the position shown in Fig. 48 
and the water in the burette B is allowed to run back into the 
level-bottle L and is then poured out of L. The level-bottle is 
then filled with water that has been saturated with the gas 



88 GAS ANALYSIS 

mixture that is to be analyzed (see p. 59), and the burette B 
is filled with this confining liquid up to the mark on the capil- 
lary just below the stopcock J. The tube N is now connected 
with the pipe or gasometer from which the sample of gas is to 
be drawn, the stopcock K is opened and somewhat more than 
100 cubic centimeters of the sample is drawn into the burette B. 
The stopcock K is then closed and exactly 100 cubic centimeters 
of gas is measured off in B in the manner described on p. 59, 
the excess pressure being released by turning / to the position 
shown in the figure. The stopcock / is then turned to such 
position that the burette B communicates with the absorption 
pipette E, the level-bottle L is raised and the stopcock of the 
pipette is carefully turned to position II, Fig. 47, and a small 
amount of gas just sufficient to drive the absorbent downward 
out of the left hand capillary tube below the stopcock is allowed 
to enter the pipette. The stopcock is then turned to position I, 
Fig. 47, and the gas sample is driven over from the burette 
into the pipette at such speed that the total sample will pass 
into the pipette in about two minutes. The stopcock of the 
pipette is then turned to position II, Fig. 47, and the gas, which 
now occupies the space FF, Fig. 47, is drawn back into the bu- 
rette by lowering the level-bottle, the liquid in the pipette being 
carefully drawn up into the two capillary tubes below the stop- 
cock until it stands just below the stopcock in each tube. The 
stopcock is then closed. In the determination of carbon dioxide 
a single passage of the gas into the pipette suffices for the com- 
plete removal of the constituent, and the diminution in volume 
is read in the burette B after the water has been allowed to 
run down for two minutes. In the absorption of oxygen by 
alkaline pyrogallol and of carbon monoxide by ammoniacal 
cuprous chloride, it is necessary to pass the gas twice through 
the pipette. In such case, by suitable manipulation of the 
stopcocks, the gas sample after being drawn back from the 
pipette the first time is immediately passed through it a second 
time. In the determination of the two gases in question the 



GAS ANALYSIS OVER WATER 89 

second passage of the sample may be more rapid than the first 
(about one minute). The sample is then drawn back into the 
burette B and is measured in the usual manner, the water being 
allowed to run down one minute before each final reading. 

After the absorption of the first constituent in the pipette E, 
the second is absorbed in F and the third in G. The three gases 
that are most usually determined with the Orsat apparatus 
are carbon dioxide, oxygen and carbon monoxide in the order 
named. The pipette E contains potassium hydroxide (see p. 2 25) , 
F contains alkaline pyrogallol (see p. 160), and G is filled with 
ammoniacal cuprous chloride (see p. 232). If the gas residue 
contains combustible constituents that are to be determined, 
the combustion apparatus is connected with the capillary tube M 
and the gas in the burette B is driven into the combustion pi- 
pette by turning the stopcock / to the position shown in Fig. 48 
and raising the level-bottle L. If only a portion of the residue 
is to be used for analysis by explosion, the larger part of the 
gas residue may be passed into the pipette E. The smaller por- 
tion of the gas that is to be exploded is then measured in B, 
the stopcock / is turned to the position shown in Fig. 48 and 
air is drawn in through M until the total gas volume amounts 
to nearly 100 cc. / is then closed, the explosion pipette is con- 
nected to M and the mixture of combustible gas and air is 
driven over into the pipette. 

The case containing the apparatus is 57 cm. high, 27 cm. 
wide and 16 cm. deep. The panels forming the front and back 
of the case are removed when the apparatus is in use. As 
illustrative of the accuracy and uniformity of the results 
yielded by this apparatus the following analyses of a mixture 
of carbon dioxide, oxygen, and carbon monoxide may be cited. 

I II III IV 

Carbon dioxide, per cent 3.1 3.1 3.2 3.1 

Oxygen 6.0 6.0 5.9 5.9 

Carbon monoxide, " 22.5 22.6 22.6 22.7 



CHAPTER VII 

THE HEMPEL APPARATUS FOR EXACT GAS ANALYSIS 
WITH MERCURY AS THE CONFINING LIQUID 

On account of the solubility of gases in water no great accuracy 
is attainable when this is used as the confining liquid even when 
it is saturated with the gas mixture being analyzed. If very 
accurate results are desired, the apparatus must unquestionably 
be filled with mercury. Some years ago it was difficult to obtain 
glass stopcocks that were perfectly tight, but the manufacture 
of glass apparatus has been so greatly improved of late that 
satisfactory instruments can now easily be procured. Com- 
plete certainty that the apparatus is absolutely tight is, how- 
ever, assured only by the use of apparatus that contains no 
stopcocks or rubber connections whatever, and in which all 
joints are made by fusing the glass tubes together. 

A. APPARATUS WITH RUBBER CONNECTIONS AND 
GLASS STOPCOCKS 

I. Gas Burettes with Correction for Variations in Temperature and 
Barometric Pressure 

Pettersson 1 was the first to show that by means of a tube 
inclosing a volume of gas it is easy to compensate the error which 
would result from variations in the pressure and temperature 
of the atmosphere. Extreme accuracy in gas analysis can be at- 
tained by the use of apparatus that is filled with mercury and is 
provided with such a compensating tube, the results with such 
an instrument being quite as exact as those obtained with the 
more elaborate apparatus for exact gas analysis described on 

1 Zeitschrift fur andytische Chemie, 25 (1886), 467. 
90 



GAS ANALYSIS OVER MERCURY 91 

p. 99, provided always that the stopcocks and rubber connections 
are perfectly tight. Three different forms of gas apparatus with 
temperature and pressure correction are shown in Fig. 49, the 
measuring tubes being varied to accommodate gas volumes 
of different sizes. Fig. 49, I, shows the apparatus intended 
for the measurement of gas volumes up to 100 cc. Fig. 49, 




FIG. 49 

II, may conveniently be used when the gas volume amounts 
to about 150 cc. In Fig. 49, III, is shown an instrument which 
was specially constructed for the examination of gases evolved 
from bacteria, the gas volumes here usually not exceeding 10 cc. 

The instruments consist of the graduated measuring tubes A, 
the correction tubes B, the manometer tubes F, and the level- 
bulbs G. The measuring tubes and level-bulbs are mounted 
in suitable iron feet. The measuring tubes and the correction 



92 GAS ANALYSIS 

tubes stand in the wide glass cylinders C, which are filled with 
water to insure that these two tubes are at all times at the same 
temperature. The measuring tubes are closed at the top by a 
double Greiner-Friedrichs glass stopcock, the construction of 
which is shown in Fig. 49, IV. 

The correction tube B and the manometer tube F are made 
from plain glass tubes fused together in the form shown in the 
cut. g is a small capillary tube. The manometer tubes are 
U-shaped, and are somewhat widened at k and i, these two 
widened portions having marks scratched on the glass at exactly 
the same height. The manometer tube is joined to the measur- 
ing tube by means of a piece of rubber tubing connecting the 
end of the capillary / with the tube a of the stopcock. The 
reason for making the manometer tube so long lies in the fact 
that otherwise, if the apparatus is carelessly handled, the mer- 
cury might easily be driven from the manometer tube into the 
burette or the correction tube. With the arrangement shown 
in the figure this is almost impossible, since the difference in 
pressure must be more than half an atmosphere before the 
mercury can pass over into either tube. The manometer tube is 
made completely of glass to prevent the mercury being con- 
taminated with the dirt from the interior of a rubber connection. 
If the burette has become dirty, the manometer tube is removed, 
and the rest of the instrument may then be cleaned without dan- 
ger of any change taking place in the gas volume inclosed in 
the correction tube. 

To prepare the apparatus for use, draw some distilled water 
through the capillary g into the correction tube B, and also 
moisten the walls of the measuring tube A with a drop or two 
of water. Fill the level-bulb G with mercury, and turn the glass 
stopcock to the position shown in DI. Then by raising the 
level-bulb drive the mercury over into the manometer tube 
until the latter is filled up to the marks on k and i. 

Before proceeding with the analysis, the volume of the mano- 
meter tube from the mark on k to the point a must be ascertained. 



GAS ANALYSIS OVER MERCURY 93 

To do this, draw over the mercury in the manometer until it 
reaches #, then turn the stopcock D until it has the position of 
DZ, and now draw any desired volume of air into the burette. 
Leaving the stopcock open, read off this volume of air on the 
scale of the burette, the air here being, of course, under the pre- 
vailing pressure of the atmosphere. Turn stopcock D so that 
the burette communicates with the manometer tube, and drive 
the air over into this latter tube until the mercury in it stands 
at equal height in its two branches; that is, at the marks on k 
and i. The difference between the two readings on the measur- 
ing tube, provided the tube g remains open, gives the volume 
of the manometer from the mark on k up to a. 

Correction tube B may be used in either of two ways. We 
may inclose within it an indeterminate amount of air by simply 
fusing together the end of the tube g so that the volume in the 
correction tube will correspond to the barometric pressure and 
temperature prevailing at the time of operation, or we may fill 
B with such an amount of air that the apparatus will indicate 
directly gas volumes reduced to standard conditions that is, 
to o C. and 760 mm. pressure. In the latter case, the gas will 
have at the ordinary temperature of the room a pressure some- 
what above that of the atmosphere. In the former case the ba- 
rometer and the thermometer must be read at the time the tube g 
is fused together, so that we may be able to correct gas volumes 
whenever this is necessary. 

In many cases it is highly desirable to so arrange the ap- 
paratus that the reading on the measuring tube A corresponds 
directly to volumes at o C. and 760 mm. pressure. To accom- 
plish this a piece of rubber tubing is slipped over the end of the 
capillary tube g and fastened firmly in place by a wire ligature. 
By lowering the level-bulb, mercury is drawn over into the 
manometer tube until it reaches the capillary I, and the burette 
is then allowed to stand for two hours in a room of fairly con- 
stant temperature. The stopcock D is then opened so that the 
contents of the burette are in free communication with the 



94 GAS ANALYSIS 

atmospheric air. As soon as one is convinced that all parts 
of the apparatus are at the same temperature, the gas volume 
in the burette is read exactly, and the temperature and baro- 
metric pressure are noted. The thermometer and barometer 
should stand in the same room with the apparatus. The stop- 
cock D is closed and the volume which the gas would occupy 
at o C. and 760 mm. barometric pressure is now calculated. 

Example. The gas volume is 97 cc., the barometric pres- 
sure 753.3 mm., and the temperature 8.75 C. The space from 
k to a in the manometer has previously been determined and 
found to be 1.8 cc. The tension of the water vapor at 8.75 C. 
is 8.4 mm. The corrected volume is 92.1 cc. 

Since, however, in making measurements with the correction 
tube, the gas fills the space from k to a, this volume must be 
subtracted from the above result: 

92.1 - 1.8 = 90.3 cc. 

In order now to adjust the gas volume in the correction tube 
so that readings of volumes in the burette will be reduced at 
once to standard conditions, the stopcock D is turned so that 
the burette communicates with the manometer tube, and the 
gas in the burette is compressed by raising the level-bulb G 
to the volume which it has been calculated that it would 
occupy at o C. and 760 mm. pressure. The mercury in the 
manometer tube is, of course, forced out of equilibrium by this 
operation. Air is now blown into the correction tube through 
the rubber tube at g until the mercury stands at the same height 
in the two branches of the manometer tube, and the rubber 
tube is then closed by means of a strong pinchcock placed di- 
rectly above the end of g. 

A rubber tube cannot remain tight for any length of time, 
and therefore the glass tube g must be fused together. This 
cannot be done at once because of the high pressure of the air in 
the correction tube, but the operation may easily be performed 
by first removing the rubber tube joining the manometer tube 



GAS ANALYSIS OVER MERCURY 95 

with the burette at a and then placing the correction tube B 
in a freezing mixture of salt and ice, allowing it to stand therein 
until the mercury in the manometer shows that the pressure 
on the inside of the correction tube is smaller than that of the 
external atmosphere. The tube g can now be heated by means 
of a blast lamp and drawn out and fused together directly be- 
low the rubber tube which is upon it. 

There is danger that the glass tube g may crack when it is 
heated. This can be avoided by painting it with a thin emul- 
sion of Plaster of Paris stirred up with water, leaving the place 
where the tube is to be drawn out uncovered by this coating. 
The Plaster of Paris offers an excellent protection against the 
overheating of that part of the glass tube which it is not desired 
to soften and can afterward easily be removed with the aid of 
water. 

The correction tube, after being thus adjusted, is again joined 
to the burette. The readings of gas volumes in the burette 
now give directly the volumes under standard conditions, no 
matter how great may be the variations of temperature and 
pressure, provided always that in making the measurements 
the stopcock is turned to the position of D\ and the mercury 
in the manometer tube is brought to the marks k and i by ex- 
panding or compressing the gas in the measuring tube. The 
exact adjustment of the mercury in the manometer tube is 
effected by raising or lowering the level-bulb G until the mercury 
stands nearly at the marks k and i, then closing the stopcock n 
and turning the screw o so as to exert greater or less pressure on 
the piece of rubber tubing against which it plays. This piece of 
rubber tubing, as is shown in the figure, connects the lower end 
of the burette with the stopcock n. In this manner the surface 
of the mercury in the two arms of the manometer may be brought 
exactly to the same level. This style of adjustment is original 
with Pettersson and enables us to effect slight changes in the 
size of the gas volume in a most convenient and rapid manner. 
In all cases where rubber tubing must withstand considerable 



96 GAS ANALYSIS 

pressure it is desirable to use enamelled rubber tubing which, 
although not quite as elastic as the ordinary kind, will easily 
withstand a pressure of several atmospheres. 

//. The Absorption Pipettes 

On account of the great differences in pressure caused by col- 
umns of mercury of only moderate height it becomes necessary 




FIG. 50 

to give to these absorption pipettes, which are partially filled 
with mercury, a form somewhat different from that adopted 
for the pipettes containing aqueous solutions. 

The Simple Mercury Absorption Pipette 

This consists of two bulbs, a and b, Fig. 50, joined together 
by a piece of enamelled rubber tubing. The bulb a has a capacity 
of about 130 cc. and b a capacity of about 150 cc. 



GAS ANALYSIS OVER MERCURY 



97 



The Simple Mercury Absorption Pipette for Solid and Liquid 

Reagents 

This resembles the pipette just described, except that the 
bulb b, Fig. 51, is cylindrical in form and has at its lower ex- 
tremity a cylindrical neck, i, through which the bulb can be 
filled with solid substances, i is then closed with a cork or 
rubber stopper held in place by a wire ligature. 




FIG. 51 



The Mercury Absorption Pipette with Absorption Bulb 

This pipette has in addition to the two bulbs a and b, Fig. 52, 
a third bulb c filled with broken glass or with glass beads. The 
advantage of this small bulb lies in the fact that when the gas 
is driven over into the pipette, the reagent which the latter 
contains clings to the small pieces of glass in c, and causes a 



9 8 



GAS ANALYSIS 



more complete absorption of that constituent of the gas mix- 
ture which is to be removed. The pipette has, however, one 
drawback: with viscous reagents bubbles of gas are liable to 
cling to the broken glass in c. 

The mercury pipettes are manipulated in exactly the same 
manner as the pipettes for aqueous solutions above described, 
except that here only small quantities of the reagent are em- 
ployed in crder to reduce the error that is caused by the solu- 




FIG. 52 

bility in the reagent of those gases which are not directly ab- 
sorbed by it. This erjor can be still further lessened by intro- 
ducing into the gas pipette an amount of reagent sufficient for 
two analyses of the gas mixture in question. In the first analysis 
the reagent becomes saturated with those gases for which it is 
not an absorbent, and the error due to solution of the gases in 
the reagent is thus minimized in the second analysis. The re- 
agents are introduced into the gas pipette by means of a small 
pipette inserted in the rubber tube b. 



GAS ANALYSIS OVER MERCURY 99 



B. APPARATUS FOR EXACT GAS ANALYSIS WITHOUT RUBBER 
CONNECTIONS OR STOPCOCKS 

Experience has shown that even the best glass stopcocks 
cannot be relied upon with certainty for any considerable 
length of time, and rubber connections will allow small quanti- 
ties of gas gradually to pass through them. It is therefore 
apparent that an apparatus which contains no stopcocks or 
rubber connections whatever possesses decided advantages 
over one in which errors arising through leakage are liable to 
occur. 

The wonderfully simple and exact gasometric methods de- 
vised by Bunsen fulfill completely these demands, but unfortu- 
nately the rapid performance of a large number of exact analyses 
is not possible with his apparatus. 

The method devised by Doyere * resembles that of Bunsen, 
in that the analysis is carried out in glass vessels fused together, 
and all ground joints and rubber connections are avoided: it 
has, however, the fault that great accuracy can be obtained 
only by the use of very cumbersome apparatus. 

By the introduction of a different manner of measuring and 
a somewhat changed construction of the necessary absorption 
pipettes, Hempel has endeavoured to improve the Doyere 
method, so that, in its changed form, rapid and very exact 
work may be possible without the use of delicate physical in- 
struments. 

Bunsen measures the gases under varying pressure and vary- 
ing volume, and Doyere measures them under constant pres- 
sure and varying volume, while in the method about to be 
described the measurements are made under constant volume 
and varying pressure. Following Boyle's law, the values so 
found bear the same proportion to one another as do gas 
volumes under the same pressure. 

1 Ann. chim. phys. [3] 28, (1850), p. i. 



ioo GAS ANALYSIS 

Doyere 1 measures the gases in a Bunsen eudiometer, and 
he avoids correction for pressure by joining the eudiometer 
with an iron holder having a screw attachment, by means of 
which the mercury in the tube and in the suitably formed trough 
may be brought to the same level. The readings are made 
with a special telescope of great exactness. The absorptions 
are effected in Doyere's improved Ettling gas pipette. 

The manipulation of the pipettes demands that the eudi- 
ometer at some place in the mercury trough be brought wholly 
beneath the level of the mercury, and further, that the suction 
tubes of the pipettes be as long as the eudiometer. From these 
two particulars it results that when a very deep trough is used, 
the pipettes are very unwieldy and easily broken, or that when 
a shorter eudiometer is employed, a sharp reading of the scale 
can be made only with the most perfect instruments, since it 
must be possible to measure with exactness tenths of a milli- 
meter. 

Doyere states that the measuring tubes used by him have a 
length of 20 cm. and an internal diameter of 15 mm. For large 
gas volumes he uses vessels similar to those employed by Bunsen 
for this purpose, the lower part being cylindrical and gradu- 
ated, and ending above in a bulb. 

The method here to be described permits, by the employ- 
ment of spherical measuring vessels, the use of a shallow mer- 
cury trough and of shorter, more easily manipulated, and less 
fragile gas pipettes, and a measurement more than three times 
as sharp, since with this apparatus, if the gas at the beginning 
of the analysis nearly fills the bulb at atmospheric pressure, the 
scale has an available length of 760 mm. while Doyere's measur- 
ing tube is only 200 mm. long. 

The measurements are made at constant volume, varying 
temperature, and varying pressure. This is accomplished by 
placing the gas in small glass bulbs which can easily be brought 
into communication with the manometer tube, by then ex- 

1 Loc. cit., also Fehling's Handw'drterbuch der Chemie, vol. i, p. 512. 



GAS ANALYSIS OVER MEfcURl?,J , : i>tii> 

panding the gas to a certain volume by lowering a movable 
vessel filled with mercury, and finally reading on the manom- 
eter tube the pressure under which the gas now stands. Ac- 
cording to Boyle's law the values thus obtained bear the same 
proportion to one another as do gas volumes under the same 
pressure. 

The absorptions are effected in gas pipettes to be described 
later. 

THE MEASURING APPARATUS 

This (Fig.* 53) consists of an iron mercury trough A (on ac- 
count of the presence of water, wood cannot be used, since it 
would swell and change form), of a glass tube D graduated in 
millimeters and from 76 to 80 cm. long and further, of the 
wooden stand G and the water reservoir E. The sides of the 
water reservoir E are glass panes, one of which e extends only so 
deep into the mercury as to leave room to bring the capillary 
of the pipette B under it into the measuring bulb C. 

By placing the measuring bulb upon the rubber stopper a 
in the mercury trough it can always be brought, by means of 
the holder/, into mercury- tight connection with the graduated 
tube D. The tube b and the J_-piece d are made of iron. D is 
connected with an arm of d by means of a piece of enamelled 
rubber tubing, or ordinary rubber tubing so wrapped as to 
enable it to resist the pressure of the mercury. A piece of 
enamelled rubber tubing joins the other arm to the movable 
level-bulb H, but between d and m there is introduced the 
Pettersson device for the fine adjustment of the mercury. (See 
Fig. 106.) 

In making the measurement, the measuring bulb C is brought 
into the position shown in Fig. 53, and is pressed down tightly 
upon the rubber stopper a by means of the clamp /. Mercury 
is then drawn out through d until the meniscus of the mercury 
in the measuring bulb lies nearly tangent to the horizontal hair 
of a magnifying glass which is fastened to the apparatus op- 







FIG. 53 



GAS ANALYSIS OVER MERCURY 103 

posite /. This glass is not shown in the figure, m is then closed 
and the exact adjustment of the height of the mercury at / is 
effected by turning the screw n. 

The height of the mercury in the manometer tube D is now 
read with a cathetometer, and the pressure of the gas in the 
bulb is then calculated. 

Since the space in the bulb is kept saturated with water 
vapor by moisture in the bulb, the corrected pressure of the 
gas in the bulb is ascertained by use of the equation 



in which b is the observed barometric pressure, m the pres- 
sure of water vapor at the temperature of the water in the 
reservoir E, and d the pressure in the manometer D. 

THE MEASURING BULB 

The measuring bulb E (Fig. 54) is fastened to the iron holder 
g by means of the projecting tubes r and s . r, which is closed at 
the top, is about 5 mm. long and s about 30 mm. At from 5 to 7 
mm. below the bulb, 5 is widened into a collar x by softening 
the glass tube in the blast-lamp flame and pressing it together. 
The iron holder g has at t a thick perforated sheet-iron cap for 
holding r. The holder bends around the bulb and is supplied 
at the lower end with the perforated iron plate u, which is bent 
at a right angle, and holds the projection s. u may be set where 
desired by means of the screw v, to which the slot through which 
it passes gives a play of several millimeters. 5 projects 4 to 
5 mm. beyond the plate u. The iron collar y is fastened to g 
in such a position that it just slips under the fork / when the 
holder and bulb are placed over the end of the iron tube passing 
through the rubber stopper m, and are firmly pressed against 
the rubber. The fork is firmly fastened to the slide i, which 
can be moved up and down by the screw h. By screwing the 
slide down, the measuring bulb can be pressed against the rub- 



IO4 



GAS ANALYSIS 




her stopper and a tight con- 
nection with the barometer tube 
thus be obtained. A scale upon 
the slide i and its guides makes 
it possible to bring the bulb at 
different times into exactly the 
same position as regards the 
millimeter scale of the ba- 
rometer. 

The total height of the meas- 
uring bulbs varies from 7.5 to 
9.5 cm. 

Since the walls of the measur- 
ing bulbs are only as thick as 
those of ordinary bulb pipettes, 
it was thought possible that, in 
the measurement of very small 
gas volumes, the volume of 
the bulb might be decidedly 
changed, since under such con- 
ditions it is exposed to nearly 
the full pressure of the atmos- 
phere. 

To settle this question, Hem- 
pel determined the volume of 
the bulb, first empty and then 
filled with gas, in a stereometer, 
and it was found that even with 
large bulbs of 100 cc. capacity 
no measurable difference of vol- 
ume could be detected; hence 
even thin-walled glass bulbs 
may be used without hesitation 
for these measurements. 

Curiously enough, it is quite 



GAS ANALYSIS OVER MERCURY 



105 



difficult to lower the measuring bulb through the water in E 
(Fig. 53) down into the mercury below without some water 
getting into the inside of the bulb. . If this should happen, 
exact reading would, of course, be impossible. Tfye operation 
can be performed, however, by bringing the measuring bulb 
into two porcelain crucibles placed one within the other in the 
manner shown in Fig. 55, and then filling these two crucibles 
with mercury. When these are lowered through the water 
into the mercury the larger crucible A is first removed, and 
then the crucible B is lowered away from the mouth of the 





FIG. 55 



FIG. 56 



bulb. The opening in the bulb is now below the surface of 
the mercury, and yet no water has entered it. 

By means of the instrument shown in Fig. 56 the air may be 
sucked out of the measuring bulb, and the gas sample can then 
be transferred to the bulb by means of one of the pipettes de- 
scribed below. 

GAS PIPETTES FOR LIQUID ABSORBENTS 

The gas pipettes were devised by Ettling and were first used 
by Doyere as absorption vessels for gas analysis. 

They consist of two bulbs a and b (Fig. 57), of the same size, 
joined together by the tube c and ending in the bent capillary 
tube d. A very small bore thermometer tube, and not a tube 



io6 



GAS ANALYSIS 



of i mm. bore as Doyere suggests, is used as the capillary, thus 
making it easy to avoid introducing absorbent into the measur- 
ing bulb or leaving any considerable quantity of gas in the 
pipette. 

Gases move rapidly in capillary tubes, but liquids, especially 
concentrated solutions of salts, move very slowly; hence it is 
easily possible to bring the gas residue in the pipette to less than 
f a cubic centimeter without danger of the absorbent en- 
tering the measuring 
bulb. It is almost im- 
possible to do this when 
wider glass tubes are 
used. 

The pipettes must 
be so made that the 
distance a (Fig. 57) is 
only as large as or 
smaller than ft: the 
capillary must be bent 
close to the bulb b. 
The pipettes are fas- 
tened to the wooden 
standard in such a po- 
sition that the capillary 
d comes to within a few 
millimeters of the bottom of the mercury trough when the 
pipette is placed in the position shown in Fig. 53. 

The bulbs of the pipettes must be considerably larger than 
the volume of the gas to be brought into them. The incon- 
venience of carefully cleaning the pipette after the absorption 
is avoided by using a special pipette for each reagent. Pipettes 
of very different sizes are employed, the sizes depending natu- 
rally upon the dimensions of the measuring bulbs. 

To bring a measured amount of the absorbent into the pi- 
pette, which is first filled with mercury, connect it by means of 




FIG. 57 



GAS ANALYSIS OVER MERCURY 



107 



a piece of rubber tubing e (Fig. 39) with the small burette / 
containing the reagent and supported by the clamp g. Open 
the pinchcock h, slip a rubber tube over the burette at i, and 
by suction so exhaust the air in the burette that any gas re- 
maining in the pipette will be drawn through the capillary x and 
through the absorbent. The pipette is thus completely filled 
with mercury. Stop the suction as soon as the mercury is visible 
above the rubber e, put the rubber tube on the pipette at /, and 
draw the mercury back to the capillary. Note the height of 
the absorbent in the burette, and then suck the desired amount 
of the same through the capillary d into the pipette. At the 
moment when the necessary amount of reagent has passed over, 
bring a drop of mercury into the burette at i. 

The amount of the absorbent introduced may be sharply de- 
termined by drawing the mercury into the pipette until the 
reagent is again visible in the capillary d, and then noting the 
height of the reagent in the burette. 

The bent capillary tube of the pipette is cleaned and freed 
from all traces of reagent by lowering the tube into a beaker 
filled with distilled water, and then drawing water into the 
capillary and driving it out again by sucking and blowing on a 
rubber tube attached to 
the open end of a. 

The pipette thus pre- 
pared for the analysis con- 
tains mercury between v 
and w, between w and x 
the absorbent, and from x 
to y mercury (Fig. 39). 

GAS PIPETTES FOR SOLID 
ABSORBENTS 



To bring the gases un- 
der examination into con- 
tact with solid absorbents, 




FIG. 58 



loS 



GAS ANALYSIS 



the form of pipette shown in Fig. 58 is used. In this the 
tube c has a branch tube e through which solid substances, 
such as sticks of phosphorus, are introduced into the bulb b; 




FIG. 59 

e is then closed at / with a cork, and the pipette is filled as 
usual with mercury. When a gas is drawn in, the solid sub- 
stances remain in the bulb b, and so come into contact with 
the gas. 



GAS ANALYSIS OVER MERCURY 109 



THE ABSORPTION 

The gas pipettes already described are used for the absorp- 
tions, the manipulation being shown in Fig. 59 and Fig. 60. 

Figure 59 gives the position in which it is possible to bring 
the gas completely into the pipette. The measuring bulb is 
here brought below the surface of the mercury and the gas is 
drawn into the pipette by sucking with the mouth on a rubber 
tube attached to m. The suction is discontinued at the moment 
when the mercury begins to flow from the capillary into the 
bulb of the pipette. 

The pipette then contains (see Fig. 57) mercury from v to 
w, absorbent from w to x, gas from x to g, and mercury from g 
to z, so that the pipette, after it is taken out of the mercury 
trough, may be vigorously shaken and a rapid absorption ef- 
fected. 

To drive the gas from the pipette back again into the measur- 
ing bulb, the apparatus is brought into the position shown in 
Fig. 60. 

In the beginning it is necessary to blow into the pipette at 
m to set the gas in motion; when it has once started, the mer- 
cury in the measuring bulb acts with an aspirating effect, so 
that the gas passes over of itself. At the moment when the 
absorbent has risen to about i cm. from the end of the 
capillary in the measuring bulb, the capillary is lowered 
under the mercury, and mercury is drawn into the capillary 
by sucking on the rubber tube attached to m. In this manner 
the entering of reagent into the measuring bulb may be avoided 
with certainty. 

If a gas thread about i cm. long remains in the capillary, 
this corresponds to approximately o.ooi cc. of gas, since the 
total 35 cm. length of the capillary has a volume, determined 
by weighing the mercury which it holds, of 0.038 cc. Conse- 
quently no appreciable error arises from this source. 

The analysis is made as follows: 



no 



GAS ANALYSIS 



Fill the carefully cleaned and moistened measuring bulb 
with the gas under examination by lowering the bulb into the 
mercury in the trough, drawing out the air in it with a gas 




FIG. 60 



pipette, and bringing the gas into the bulb either by means of 
a delivery tube brought under the mouth of the bulb or by 
means of a gas pipette. 



GAS ANALYSIS OVER MERCURY in 

The necessary measurements, absorptions, and explosions 
now follow, their order being determined by the nature of the gas. 

Since difficulties arise only in the use of fuming sulphuric 
acid over mercury, while all other reagents can easily be manip- 
ulated in the manner already described, the reader is referred 
to Chapter XIII for descriptions of methods of absorption of 
the various gases. 

The heavy hydrocarbons cannot be absorbed with fuming 
sulphuric acid in the manner described, because, on bringing to- 
gether the fuming acid and mercury, sulphur dioxide is evolved 
even in the cold, and acid sulphates are formed which, upon 
long standing, separate as thick crusts and obstruct the pipette. 
Since, however, the gases that are not absorbable by the fuming 
acid are very insoluble in the same, a pipette completely filled 
with the acid may be used, the mercury here coming into con- 
tact with the sulphuric acid only in the capillary tube. If care 
be taken in the manipulation that no mercury passes over from 
the trough into the pipette, and if, after using, all mercury be 
removed from the capillary by means of a common suction 
pipette attached thereto, so that sulphuric acid alone remains 
in the pipette, a stoppage of the capillary, which, when it has 
once taken place, is difficult of removal, need not be feared. 

To protect the lungs from the fumes of the sulphuric acid, a 
glass tube filled with pieces of caustic potash is interposed be- 
tween the rubber suction tube and the pipette. 

Unless very accurate results are desired, it is sufficient to 
make all readings with the unaided eye, for if the eye be brought 
only approximately to the same plane with the surface of the 
mercury column that is to be read, the results thus obtained 
are quite close to the truth. 

The accuracy of the analysis may easily be greatly increased 
by using a number of measuring bulbs of different sizes and 
determining their volumes by filling them with mercury and 
weighing the mercury. The gas to be analyzed is then first 



112 GAS ANALYSIS 

brought into the largest bulb and one or more of its constitu- 
ents are determined. If the remaining volume now amounts 
to only a half or two-thirds of the original volume, this residue 
is introduced into a smaller measuring bulb. This procedure 
permits of the use of the total length of the manometer tube D 
(Fig. 53) in making the measurements, and consequently in- 
sures much greater accuracy in the readings. 



CHAPTER VIII 

THE CONSTRUCTION AND CONNECTION OF 
APPARATUS 

Glass Blowing. It is of great convenience to the gas ana- 
lyst to be able to make simple forms of glass apparatus and to 
repair broken parts. The elements of glass blowing are clearly 
described in such books as that by Shenstone, and with prac- 
tice it is possible for almost every chemist to develop consider- 
able facility in glass blowing. 

The blast-lamp should have cocks on the lamp itself for the 
easy regulation of the supply of gas and air blast. It should 
give with full blast pressure a colorless flame about thirty cm. 
long, and with diminished blast pressure a yellow-tipped flame 
about forty cm. long. On cutting down the gas and air pressure, 
the lamp should furnish a small, sharp pointed, colorless flame 
about five cm. long. 

The glass tubing should be easily fusible and the ordinary 
sizes, from six mm. to twenty mm. in diameter, should have a 
wall about one mm. thick. Glass tubes or glass parts that 
are to be fused together should be of the same kind of glass, for 
joints made of different kinds of glass will usually easily break 
apart. All joints should be highly heated and thoroughly blown 
out, and should be carefully annealed by holding them in the 
luminous flame of the lamp until they are thoroughly coated 
with soot and then allowing them to stand until cold. 

Amateurs that have difficulty in blowing glass bulbs in the 
middle of tubes will find it convenient to order from a glass 
manufacturer a supply of thin walled glass bulbs, of from four 
cm. to seven cm. in diameter, with side tubes of from seven mm. 
to twelve mm. external diameter and each about fifteen cm. long. 

"3 



114 GAS ANALYSIS 

Since some find difficulty in properly bending capillary tub- 
ing for the Hempel apparatus it may be stated that such tubing, 
which should be six mm. external diameter with one mm. bore, 
may easily be bent, without blowing, by first warming it care- 
fully in the luminous flame of the blast lamp, and then heating 
the spot at which the bend is to be made in a blast flame 
about two cm. wide, turning the tubing during the heating. 
As soon as the tube softens, it is bent directly to the desired 
angle as one would bend a piece of glass rod. 

Mounting of Apparatus. If glass apparatus is to be mounted 
on a frame or standard, it should be fastened at only a few 
places so as to allow of as free expansion as possible, and it is 
best secured in position by fastening to the support a metal band 
that passes around the glass tube, but does not touch it, and 
then filling the intervening space between the metal strap and 
the tube with Plaster of Paris. 

Rubber Connections. If glass tubes are to be joined to- 
gether by rubber tubing, the ends of the tubes should be rounded 
in the flame, and should be brought close together within the 
piece of rubber tubing. To secure the rubber tubing in place, 
it may be fastened by wire ligatures. For this purpose copper 
wire about one mm. in diameter is most suitable. Each ligature 
should consist of only one turn of the copper wire around the 
tube, the ends being drawn and tightly twisted together by 
means of a pair of pliers. Long rubber connections should be 
avoided, not merely because the rubber tubing is somewhat por- 
ous, but also because air in the tube adheres tenaciously to the 
walls. A rubber tube capable of withstanding high pressure is 
needed in connecting level-tubes or level-bulbs with gas burettes 
when the apparatus is to be filled with mercury as the confining 
liquid. For this purpose the so-called enamelled rubber tubing 
about six mm. internal diameter and with a wall two mm. thick 
will be found very satisfactory. For connecting the level-bulb of 
a mercury air pump with the pump, enamelled rubber tubing 
about twelve mm. internal diameter and 2.5 mm. thickness of 



CONSTRUCTION AND CONNECTION OF APPARATUS 115 

wall may be employed. The enamelled tubing is superior to the 
ordinary pressure rubber tubing with very thick wall, because 
its larger internal diameter permits free flow of the mercury, and 
its smooth interior surface avoids the fouling of the mercury 
by particles of the rubber. It has been found in practice that it 
will easily withstand a working pressure that rises at times to 
five atmospheres. 

Stopcocks. Hollow-blown stopcocks are so perfectly made 
that they may be employed with very slight danger of leakage 





FIG. 6 1 FIG. 62 

provided they are properly lubricated. The Greiner & Fried- 
richs form of stopcock of the form shown in Fig. 61 and Fig. 62 
is superior to the stopcock with straight bore because it avoids 
the danger of leakage due to the channeling of the barrel of the 
stopcock. 

Lubrication of Stopcocks. An excellent preparation for 
the lubrication of glass stopcocks that does not deteriorate on 
keeping, does not work out at the ends of the key, and gives 
off no hydrocarbon vapors may be made as follows: Place in an 
evaporating dish twelve parts of vaseline and one part of paraf- 
fin wax. Heat this mixture over a Bunsen flame and maintain 
the contents of the dish at a temperature that will keep the 
materials fluid but will not cause the mixture to emit fumes. 
Drop in successive portions of soft, black-rubber clippings and 
stir the mixture after each addition until the rubber is com- 
pletely dissolved. After about nine parts by weight of rubber 
has been added, take out a small sample of the lubricant on 
the end of a stirring rod, allow it to cool, place it on the ball of 
the thumb, squeeze it with the end of the middle finger and 
then rapidly tap the finger upon the thumb at the point covered 



n6 GAS ANALYSIS 

by the lubricant. If on this treatment the lubricant forms light 
feathery particles that float off in the air in fine flocks the proper 
mixture has been reached. If the lubricant does not behave 
as described, stir in more rubber and test again. About ten 
parts by weight of the rubber will usually be required for the 
above amounts of vaseline and paraffin. 

In lubricating a glass stopcock, the key and barrel should 
first carefully be cleaned and then the thinnest possible film 
of vaseline be rubbed over the surface of the key of the stopcock. 
The lubricant is then rubbed over the key which is next inserted 
in the barrel and turned around until the lubricant is evenly 
distributed over the surface. 

In the Cornell laboratory, it has been found that a Greiner & 
Friedrichs stopcock of the form shown in Fig. 61, when lubri- 
cated with this mixture, will withstand a pressure of four atmos- 
pheres on one side and a Torricellian vacuum on the other for 
a considerable length of time without any leakage whatsoever. 

Another recipe for a lubricant for stopcocks is given by Keyes: 1 
26 grams of paraffin (melting point 70) is placed in a dish and 
heated until it melts, and then 18 grams of pure gutta percha 
is added in small amounts at a time, the temperature of the 
mass being held at about 150 until the gutta percha is dis- 
solved. 20 grams of a heavy mineral oil such as is supplied, 
with the Fleuss pumps is then added and the mixture is main- 
tained at a temperature of from 1 25 to 130 for four or five hours. 

If the gases or liquids that are to pass through the stopcock 
are of such nature as to cause them to attack the rubber lu- 
bricant, metaphosphoric acid may be used. The key and 
barrel of the stopcock are thoroughly cleaned and dried; the 
key is dipped into phosphorus pentoxide, is allowed to stand 
in the air until the pentoxide has taken up sufficient water to 
form metaphosphoric acid, and is then inserted into the bar- 
rel and turned until the metaphosphoric acid is spread evenly 
over the surface. 

1 J. Am. Chem. Soc., 31 (1909), 1271, 



CHAPTER DC 
PURIFICATION OF MERCURY 

Mercury that is pure will pass over a glass surfac6 without 
adhering to it or leaving a deposit upon it. If the mercury is 
contaminated with other metals there forms upon the mercury a 
layer of oxides that adhere to glass. Commercial mercury fre- 
quently contains zinc and lead, and through use in the laboratory 
it usually soon becomes contaminated with copper. These for- 
eign metals may be removed by oxidizing them and then dissolv- 
ing their oxides with an acid that does not attack the mercury. 
They may also be separated from the mercury by bringing the 
impure metal into contact with a mercurous salt and a free acid, 
which will remove from the mercury such metals as stand above 
it in the electromotive series, the foreign metals passing into the 
solution and precipitating an equivalent amount of mercury. 
Metals that stand below mercury in the electromotive series, 
such as platinum and gold, cannot be separated from the mercury 
in this manner. In such case it is best to distill the mercury un- 
der diminished pressure. It was formerly supposed that certain 
metals, such as zinc, would distill over with the mercury, but 
Hulett has shown 1 that this does not take place if bumping 
of the mercury during distillation is avo.ided. He has ascer- 
tained, however, that when the mercury is contaminated with 
dry metallic oxides, these oxides may be carried over with the 
mercury vapor. 

If the mercury is very impure a considerable portion of the 
dirt and oxides may be removed by running the mercury through 
a dry filter paper that is folded and placed in a glass funnel in 
the usual manner after the tip of the filter has been cut off. 

1 Z. physikalische Chemie, 33 (1900), 611. 
117 



n8 



GAS ANALYSIS 



The hole in the end of the filter paper should be from one to 
two mm. in diameter. The metal may then be purified by one 
of the processes described below. 

Purification of Mercury by Nitric Acid. 
If the mercury is highly contaminated 
with other metals it may rapidly be freed 
from a considerable portion of these metals 
by placing it in a bottle, covering it with a 
layer of a five per cent solution of nitric 
acid, and blowing air through the mercury 
through a glass tube. If air blast is not 
available, the mercury and acid may be 
placed in a filtering flask into the neck of 
which is inserted a one-hole stopper carry- 
ing a glass tube reaching nearly to the bot- 
tom of the flask. Upon connecting the 
side arm of the flask with a suction pump, 
air will be drawn down through the tube 
and will pass upward through the mer- 
cury. 

Further purification of the mer- 
cury by means of nitric acid may 
then be effected by use of the ap- 
paratus shown in Fig. 63. 

A is a glass tube one meter long, 
from 2 to 3 cm. wide, and fitted at 
the lower end with a cork and the 
^ bent glass tube D. B is the sup- 
f ply bottle for impure mercury, and 
C the receiver for the purified 
FIG. 63 mercury. The lower end of the 

tube from B is drawn down to a 

small opening. Some pure mercury is first poured into the 
tube D, and A is then filled with 5 per cent nitric acid, the 
acid being kept in the tube by the mercury in D. Upon allow- 




PURIFICATION OF MERCURY 119 

ing the mercury to drop from B, the purified metal passes 
slowly over into C. 

Purification of Mercury by Concentrated Sulphuric Acid 
and Mercurous Sulphate. This is a very simple and efficient 
method which yields mercury that is both dry and of high 
purity. 

The process of purification may conveniently be carried out 
in a heavy separatory funnel of from 2 to 4 liters capacity, the 
funnel being supported in a wooden stand at such a height that 
an ordinary bottle or beaker may readily be brought under 
its lower end. The funnel is first partly filled with mercury 
(impure mercury may be used here, if no purified mercury is at 
hand), and then about 500 cc. of concentrated sulphuric acid is 
poured upon the mercury and from 25 to 50 grams of mercurous 
sulphate is added. In the top of the separatory funnel is placed 
an ordinary funnel, the stem of which is drawn out to small 
diameter and turned upward. The mercury to be purified is 
poured into this latter funnel and flows slowly and in the form of 
a fine spray out of the end of the stem. It is freed from foreign 
metals that stand above it in the electromotive series by the 
action of the sulphuric acid and mercurous sulphate, and 
is thoroughly dried by passing through the concentrated acid, 
so that pure and dry mercury may at any time be drawn 
off from the separatory funnel. In starting the process, 
impure mercury which may first have been put into the funnel 
should, of course, be drawn off and run through the purifier a 
second time. The mercury in the sepajatory funnel should 
never be drawn down until it is near the stopcock, for some 
sulphuric acid might be drawn off with it. 

Purification of Mercury by Distillation. This method, 
as stated above, gives satisfactory results if the mercury is 
free from oxides and if bumping of the liquid during distilla- 
tion is avoided. If foreign oxides are present, they should first 
be removed by one of the methods described above. 

Of the many forms of apparatus that have been suggested 



120 



GAS ANALYSIS 



A W 




FIG. 64 



for the distillation of mercury 
that shown in Fig. 64 is one of 
the simplest and most satis- 
factory. All glass parts of the 
device are of Jena glass. The 
mercury is boiled in the bulb 
A which has a diameter of 
about 7 cm. The neck of the 
bulb A is fused to the outside 
of the tube G just above B, 
and has a side arm K that is 
connected with the level-bulb 
If by a piece of enamelled rub- 
ber tube. To the lower side 
of the bulb B is attached a 
tube of 5 mm. internal di- 
ameter, and 15 cm. long, and 
to this is fused the capillary 
tube C that has a bore of 
about one mm. diameter, and 
a length of about 800 mm. 
The lower end of C is bent 
upward and widened at D, 
and then is brought up over 
the middle of the box and 
turned downward at E. 

To start the distillation, dry 
mercury that has been freed 
from oxides is poured into the 
level-bulb M , and the capillary 
tube E is connected with a 
mercury pump or with an ef- 
ficient water suction pump 
if a mercury pump is not 
available. M is then raised 



PURIFICATION OF MERCURY 121 

until the mercury rises in A nearly to the top of the tube G, 
and the pumping is continued until all the air possible has 
been drawn out of B through C. M is then slipped into its 
adjustable support, and this is set at such a height in the slot 6" 
by means of a set screw that the bulb A is about half filled with 
mercury. The ring burner W is now lighted and the mercury 
carefully brought to boiling. The height of the level-bulb M 
is readjusted so that the bulb A stands half full of mer- 
cury. The vapor of the mercury passes from A down through 
G into B, and escapes through the open end of the capillary E 
into a container placed below E to receive it. 



CHAPTER X 

ABSORPTION APPARATUS FOR USE WITH LARGE 
VOLUMES OF GAS 

Gases that are very soluble in water or that are present in 
only small amount in a mixture of gases are best determined 
by passing the gas mixture through suitable absorption ap- 
paratus to remove these constituents and then ascertaining 
the quantity of the absorbed gas by gravimetric or volumetric 
methods. The total volume of the gas mixture that is passed 
through the absorption apparatus is measured by a suitable 
device, such as an experimental gas meter. The meter is placed 
before the absorption apparatus if the gas that is to be deter- 
mined is not appreciably soluble in water. Otherwise it is placed 
after the absorbent. 

This method of analysis is particularly well adapted to the 
determination of minute amounts of a gas in a gas mixture for 
the reason that the large size of the sample that may here be 
employed renders the results very accurate if the absorbed 
constituent is correctly determined. To illustrate how slight 
is the effect, upon the final result, of a considerable error in the 
measurement of the sample, let us suppose that, in the deter- 
mination of carbon dioxide in air, a sample of ten liters has been 
passed through the apparatus and the titration shows four cc. 
of carbon dioxide, or 0.04 per cent. If a mistake of 100 cc. were 
made in the measurement of the sample, which would be a very 
large experimental error, the result calculated for 10100 cc. would 
be 0.0396 per cent carbon dioxide, and for 9900 cc., 0.0404 per 
cent. To obtain the same accuracy by the volumetric analysis 
of a sample of air measuring 100 cc. the readings would have 
to be correct to the hundredth of a cubic centimeter. 

122 



ABSORPTION APPARATUS 



123 



To effect the complete absorption of a gas by a liquid, it is 
necessary that the gas be broken up into fine bubbles before 
or while passing through the absorbent, or that it remain in 
contact with the liquid for a considerable length of time. The 
former procedure, being more rapid, is usually to be preferred, 
and in the most efficient forms of absorption apparatus the gas 
enters the absorbent through small orifices in the inlet tube, or 
passes upward through a column of glass 
beads or of pieces of broken glass that are 
moistened with the absorbent. Many 
forms of the first type of absorption ap- 
paratus have been described and most of 
them are doubtless familiar to the reader. 
Special forms of such apparatus are pic- 
tured on pages 228 and 359. 

A novel form of gas washing bottle that 
has been thoroughly tested in the Cornell 
laboratory and found to be very efficient 
is shown in Fig. 65. It is a slight mod- 
ification of the spiral gas washing bottle 
recently designed by Fritz Friedrichs and 
placed upon the market by Greiner and 
Friedrichs. In preparing the bottle for 
use the stopper with the attached inner 
cylinder is removed, and the absorbing 
liquid is introduced into the outer cylinder 
in such amount that when the inner cyl- 1 
inder is replaced the liquid will stand at 
the height of the lowest spiral. The gas enters the bottle at A 
and passes into the absorbing liquid through small openings in 
the bottom of the inner cylinder. It cannot escape directly up- 
ward, but must pass around the spirals, which it does in the 
form of a procession of gas bubbles that push ahead of them 
small amounts of the absorbing liquid. The contact between 
the gas and the absorbent is intimate and of considerable 




FIG. 65 



124 



GAS ANALYSIS 



duration, and the consequent absorption is very complete. 
This form of the bottle was particularly designed for quantitative 
work. Upon removal of the small rubber stopper that is in- 
serted in A the absorbing liquid in the bottle can easily be 
removed, and the bottle be thoroughly rinsed out. If, how- 
ever, the nature of the work is such as to render undesirable 
the use of a rubber stopper in A, the tube A may be made 
somewhat longer and bent at a right angle, Fig. 66, which will 
permit of a glass-to-glass connection of the apparatus. 

If it is desired merely to remove a gas 
from a gas mixture, but not afterward to 
determine its amount, the apparatus de- 
vised by Winkler may be used. The de- 
vice, Fig. 67, consists of a Wolff bottle b 
into one neck of which is inserted the 
stem of the cylinder a. To obtain large 
surface of contact between the absorbent 
and the gas, a is filled with pieces of 
pumice-stone. The gas enters through 
the tube c which .extends downward to 
the bottom of the largest cylindrical 
portion of a. It then rises through the 
moistened pumice-stone and passes out 
through the tube e. The bottle b con- 
tains the absorbing liquid which can be 
driven up into a from time to time by 
blowing into the glass tube d, the excess 

of absorbent immediately flowing back into b when the pressure 
at d is released. 

In this Winkler absorption apparatus, however, the gas that 
rises through the cylinder a comes in contact with only such 
portion of the absorbent as adheres to the surface of the pumice- 
stone. Moreover if a large amount of gas is being removed by 
the absorbent the liquid must frequently be driven up into a 
by blowing into d. A modification of the apparatus that gives 




FIG. 66 



ABSORPTION APPARATUS 



125 



more efficient absorption and automatically renews the ab- 
sorbent is shown in Fig. 68. A Friedrichs spiral absorption 
tube fits by a ground joint into one neck of a Wolff bottle that 
contains the solution of the absorbent. Into the other neck 
of the Wolff bottle is inserted by means of a ground joint a 





FIG. 67 



FIG. 68 



short glass tube T carrying the stopcock S. Some of the re- 
agent is driven up into the absorbing cylinder by opening S 
and blowing into T whereupon 6* is closed. The gas mixture 
enters through the tube A and, passing downward in the inside 
of the spiral, it enters the tube B and passes upward through 
the open lower end of the short tube C. It then rises 



126 GAS ANALYSIS 

around the spiral carrying some of the liquid with it, and 
the non-absorbed gases escape at D. As the gas bubbles rise 
through the short tube C they draw up fresh absorbent through 
the tube B and the absorbent that has been in contact with 
the gas flows downward through the tube E into the Wolff 
bottle below. In this manner constant circulation of the ab- 
sorbing liquid is attained and the apparatus requires no further 
attention after once it has been set in action. 



CHAPTER XI 
THE COMBUSTION OF GASES 

Most gases may quantitatively be removed by absorbents, 
and for this reason the combustion method is chiefly employed 
for the determination of only hydrogen, methane and its hom- 
ologues, and at times carbon monoxide. Under certain con- 
ditions, however, it may be advisable to determine the amounts 
of other constituents of a gas mixture by direct combustion 
even although these gases may be absorbable by suitable re- 
agents. It is not always possible to ascertain from the results 
of a single combustion the percentage of each constituent in 
the gas mixture. De Voldere and de Smet 1 have developed 
certain fundamental laws which show the possibilities and 
limitations of the combustion method, and the following con- 
densation and revision of their original article has been pre- 
pared by Dr. R. P. Anderson. 

According to de Voldere and de Smet the gases that may 
accurately be determined by combustion analysis are divisible 
into three classes: 

I. Hydrocarbons. 

CnH2n + 2k, where k = i, o, -i, -2, or -3. It is convenient 
to include under this head CO, CO2, O2, .and H2 because the 
combustion equations of these gases are of the same type as 
those of the hydrocarbons, as is evident if the proper values 
are given to n and k. For example, 

if n = o and k = i CnH 2 n + 2 k becomes CoH 2 , equivalent to H2 

" k = -2 " " CiH-2, " " CO 

" k = -2 " " CoH-4, " " O 2 

= i " k = -3 " " CiH_ 4 , " " CO 2 

1 Die Analyse brennbarer Case, Z.f. analyt. Chem., 49 (1910), 661-688. 

127 



128 GAS ANALYSIS 

II. Gases containing carbon, hydrogen and oxygen. 
Formic aldehyde, CH 2 O; methyl ether, (CH 3 ) 2 O; methyl 

ethyl ether, (CH 3 C 2 H 5 )O; ethyl ether, (C 2 H 5 ) 2 O; acetaldehyde, 
C 2 H 4 O. 

III. Gases containing nitrogen. 

Nitrogen, N 2 ; nitrous oxide, N 2 O; ammonia, NH 3 ; hydrogen 
cyanide, HCN. 

Other combustible gases such as the hydrides of the fifth and 
sixth groups of the Mendeleeff periodic arrangement, halogen 
and sulphur hydrocarbon substitution products, and gaseous 
compounds of nitrogen other than those given above, yield 
combustion products that are not suited to gas-volumetric de- 
termination. The following discussion is confined to combina- 
tions of gases of the first class, finally amplified to include ni- 
trogen or one of the other nitrogen-containing gases. For 
details concerning the combustion of gas mixtures containing 
members of all three of the above classes, the reader is referred 
to the original article* 

In the combustion of a hydrocarbon four factors are deter- 
minable. These factors together with the symbols that will 
here be used to represent them are as follows : 

V, the total volume of gas to be burned; 

O 2 , the volume of oxygen necessary for the complete com- 
bustion of the gas; 

CO 2 , the volume of carbon dioxide that is formed in the com- 
bustion; 

T. C., the total contraction in volume that results from the 
combustion. 

This total contraction is equal to the sum of the volume 
of the hydrocarbon and of that of the oxygen used, less 
the volume of carbon dioxide that is formed. The water 
that is produced in the combustion condenses to the liquid 
state. 

T. C. = V + 2 - CO 2 . (i) 



THE COMBUSTION OF GASES 



129 



The complete combustion of a hydrocarbon, CnH 2 n + 2 k, 
may be expressed by the equation 



CnH 2 n + 2 k+ 



In this case: 



O 2 = nCO 2 + (n + k) H 2 O. 



CO 2 = nV 
T.c. = 2 



(2) 

(3) 
(4) 



The following table gives the values of O 2 , CO 2 , and T. C. 
per unit volume of hydrocarbons of the various groups. 

TABLE I 



Jj. 


GROUP 


2 


C0 2 


T.C. 


EXAMPLES 


I 

o 


CnH 2 n + 2k 
CnH 2 n 

fntT -n 


3n + i 


n 
n 
n 
n 
n 


n + 3 


CH 4 C 2 H 6 ,C 3 H8,H 2 
C 2 H 4 
C 2 H 2 
C0,0 2 
CO 2 


2 

3" 


2 

n + 2 


2 

3n- i 


2 

n+ i 


I 


CnH 2 n - 4 
CnH 2 n - 6 


2 

3 n-2 


2 

n 

2 

n i 




2 

3n-3 


3 


2 


2 



The four factors, V, O 2 , CO 2 , and T. C. can also be determined 
in the combustion of any mixture of hydrocarbons, and by means 
of equations expressing the relationships between these four 
factors and the unknown volumes of the gases that are present, 
the volumes can, in certain cases, be computed. A study of these 



130 GAS ANALYSIS 

equations shows that the number of gases that can be determined 
depends upon the nature of the gas mixture. The different pos- 
sibilities are discussed under the following cases: 

FIRST CASE. It is possible, by means of one complete com- 
bustion, to determine the percentage composition of a gas mix- 
ture that contains not more than two hydrocarbons of the same 
group, provided the formula of each constituent is known. 

If a gas mixture were to contain several gases of one group, 
say Group I, the equations between the knowns and unknowns 
would be derived as follows: 

Let x, y, z, . . . = volumes of the gases present 
and n, n', n" . . . = indices of gases x, y, z . . . 

Then (from Table I), 

V=x+y+z+. .. (5) 

2 .3JLl x+ 35lI y+ 3n^M z + (6) 

222 

CO 2 = nx + n'y + n"z + . . . (7) 



T .C. 



These four equations are not independent as can be shown 
by the following eliminations : 

2O 2 - V - 3 CO 2 =0(2 xEqn. 6 - Eqn. 5 - 3xEqn. 7) . (9) 
2 T. C. - CO 2 - 3 V = o (2 xEqn. 8 - Eqn. 7- 3xEqn. 5) . (10) 

Equations 9 and 10 represent the peculiar relations that 
exist between the four determinable factors when the gases be- 
long to the same group, and this relation is such that the de- 
termination of any two of these factors enables one to compute 
the other two; hence there are in reality only two independent 
equations, and not more than two gases of this group could be 



THE COMBUSTION OF GASES 



determined by a single combustion. Similar relations hold 
true for the other groups and the analogous equations are 
given in the following table: 

TABLE II 



GROUP 



EQUATIONS 



CnH 2 n -j~2 




2 T. C. C0 2 


v 3 CO 2 2 O 2 






3 


i 


CnH 2 n 




2 T. C. CO 2 


3 CO 2 2 O 2 





2 











or 3 CO 2 = 2 O 2 


CnH 2 n- 2 


V = 


2 T. C. CO 2 


V = 3 C0 2 2 2 






2 T. C. CO 2 


3 C0 2 2 2 






o 


2 




or 


2 T. C. = CO 2 






V 


2 T. C. C0 2 


_ 3 CO 2 2 O 2 


CnH 2 n , 




i 





It is apparent also that the formulas of the individual gases 
are necessary, since otherwise two new unknowns, n and n', 
would be introduced and the number of unknowns would 
exceed the number of independent equations. 

A gas mixture that rather frequently occurs in technical 
practice is one containing hydrogen, methane and ethane. 
These three gases are hydrocarbons of the same group under 
the classification that is here employed, and since they belong 
to the same group, they cannot be determined by a single com- 
bustion. //, in the analysis of this gas mixture, the results of the 
combustion are computed for hydrogen and methane alone, the 
volume of methane will be too large by twice the volume of the ethane 
that is actually present, and the volume of hydrogen will be too 
small by a volume equal to that of the ethane that is present, en- 
tirely independent of the relative percentages of each. 



132 GAS ANALYSIS 

The following calculation will make this clear: 

Let H 2 , CH 4 and C2H 6 represent the volumes of hydrogen. 

methane, and ethane in a mixture of these three gases. 

Then, giving the proper values to n, n/ and n" in equations 

7 and 8, 

T. C. = | H 2 + 2 CH 4 + ^ C 2 H 6 (n) 

and CO 2 = CH 4 + 2 C 2 H 6 (12) 

Now, let x and y represent the amounts of hydrogen and 
methane obtained when the computation is based upon these 
two gases. 

Then T. C. = | x + 2 y (13) 

And CO 2 = y (14) 

|x + 2 y =^H 2 + 2 CH 4 +fc 2 H 6 (Eqn. n Eqn. 13) (15) 

y = CH 4 + 2 C 2 H 6 (Eqn. 12 Eqn. 14) (16) 

x = H 2 C 2 H 6 (-[Eqn.i5 2xEqn.i6])(i7) 

o 

For example, if a gas mixture contains equal volumes of 
hydrogen, methane, and ethane, and the combustion data are 
computed for hydrogen and methane alone, the result would 
indicate that the gas mixture contains only methane (see 
Equations 16 and 17). 

In the analysis of such gas mixtures as coal gas, producer 
gas, or water gas the residue after the removal of the absorb- 
able constituents is frequently assumed to consist of hydrogen, 
methane and nitrogen, and a calculation of the combustion 
results is based upon this assumption. It is clear from what 
has been stated above that this assumption may lead to errors 
of considerable magnitude in the percentages of hydrogen and 
methane if ethane is present. The percentage of nitrogen, 
however, is not affected, since the sum of the percentages of 



THE COMBUSTION OF GASES 133 

hydrogen and methane apparently present is equal to the sum 
of the percentages of hydrogen, methane and ethane actually 
present. 

SECOND CASE. It is possible, by means of one complete 
combustion, to determine the percentage composition of a gas 
mixture that contains not more than three hydrocarbons, two 
of them of the same group, provided the formula of each con- 
stituent is known. 

If a gas mixture of this type were to contain two gases of 
Group I and one gas of each of the remaining groups, the equa- 
tions would be derived as follows : 

Let x, y, z, . . . = volumes of the two gases of Group I 
and the gases from the other groups respectively, and n, n', n", 
. . . = indices of gases x, y, z, etc. 

Then, 

V = x -f y + z + . . . (1.8) 



2 22 

CO 2 = nx -f n'y + n"z + . . . (20) 

T C n +3 x 4- n/ + 3 v -f n " + 2 Z + ( 2I ) 

A. \s. = ~ a> T" jf ' * ^r . - \^ A / 



But inasmuch as 
V + O 2 = CO 2 + T. C. (see Equation i) . . . (22) 

holds true for the combustion of any mixture of hydrocarbons, 
it is clear that if three of the four factors, V, O 2 , CO 2 , and T. C., 
are known, the fourth may be computed. From this it follows 
that there are really only three independent equations, and for 
this reason more than three hydrocarbons, two of them of the 
same group, cannot be determined by a single combustion. 
Moreover, as was shown under First Case, the formula of each 
gas must be known. 



134 ' GAS ANALYSIS 

THIRD CASE. It is usually possible by means of one com- 
plete combustion to determine the percentage composition of 
a gas mixture that contains not more than three hydrocarbons, 
all of them of different groups, provided the formula of each 
constituent is known. 

If a gas mixture of this type were to contain one gas from 
each group, the equations would be derived as follows: 
Let x, y, z, . . . = volumes of gases of ist, 2d, 3d ... groups 
And n, n', n" . . . = indices of gases, x, y, z . . . etc. 

Then 

V = x + y + z -f . . . (23) 

311 + i 3n' 3n" i , . 

2 = x+^- y+ ^ z+ . . . (24) 

222 

CO 2 = nx + n'y + n"z -f . . . (25) 

T .C.= ^ x+ ^ y+ ^_' z+ ... (26 ) 

222 

For the same reasons as those given under Second Case, not 
more than three hydrocarbons belonging to different groups can 
be determined, and the formula of each must be known. But 
in mixtures that would be classed under the Third Case there 
may exist a peculiar relation between the indices of the various 
gases that will render the equations indeterminate. For ex- 
ample, if a gas mixture contains one gas from each of the fol- 
lowing groups, C n H 2n+2 , C n H 2n _ 4 , and C n H 2n _-6, then 

V = x + y + z (27) 

2 O 2 = (3n + i)x + fen' 2)y + ( 3 n" 3)z (28) 
2 T.C. = (n + 3 )x + n'y + (n" i)z (29) 

CO 2 = nx + n'y + n /r z (30) 

Solving for x (or y or z), 

(4n' 3n" n)x = some expression in terms of V, O 2 , 
T. C., andCO 2 . (31) 



THE COMBUSTION OF GASES 



135 



When the relation between n, n' and n" is such that 
4 n' 3 n" n = o, or n' = , the equation is inde- 



terminate. This is true when n = n 7 = n" = i, as for example 
when the gas mixture contains methane, carbon monoxide, and 
carbon dioxide. 

Since the gases classified under the Third Case may belong 
to any one of five groups (see p. 129) there are ten possible 
combinations under this case. 

If the five groups are represented by A, B, C, D, E, and the 
indices of the three gases in the mixture are represented by 
n, n' and n" in the order of the groups, then the determinants 
and the indeterminate examples among the gases in Table I 
may be tabulated as follows: 



TABLE III 



COMBINATION 



DETERMINANT 



INDETERMINATE EXAMPLES 



ABC. 
BCD. 
CDE . 
ACE . 

ABD . 
BCE . 

A CD . 
BDE . 



ABE . 
ADE . 



j n" + n 



j m" + n 



C 2 H 6 , C 2 H 4 , 

C 3 H 8 , C 2 H 2 , C0 2 
C 3 H 8 , C 2 H 4 , 2 



' CH 4 , CO, C0 2 



136 GAS ANALYSIS 

FOURTH CASE. When a gas mixture contains hydrocar- 
bons that belong to not more than two groups, the percentage 
of each group in the mixture may be determined by means of 
one complete combustion if the general formula of each group 
is known. 

Let V be a mixture of two groups, of volumes X and Y to be 
determined, each a mixture of several gases xi, X2, x 3 , . . . and 

yi, 72, ys, . . . 

Also let HI, n 2 , n 3 , . . . and n'i, n' 2 , n' 3 , ... be the indices of 
the gases, and k and k/ the constants of the two groups. 

Then V = xi + x 2 + x 3 . . . + yi +y 2 +y 3 . . . (32) 

CO2 = ni xi + n 2 x 2 + n 3 x 3 . . . -f n'i yi + n' 2 y 2 + n' 3 ys 

... (33) 

2 T. C. = (m + k + 2) xi + (n 2 + k + 2) x 2 . . 
+ (n'i + k' + 2)71 + (n' 2 + k' + 2)y 2 . . . (34) 

2 O 2 = ( 3 m + k) xi + ( 3 n 2 + k) x 2 . . . + ( 3 n'i + k') yi 
+ 3n' 2 + k')y 2 (35) 

2 T. C. 2 V 2 =CO k(xi + x 2 + x 3 . . . ) + k'(yi 
+ y 2 + y 3 . . . ) . . . (36) 

(Eqn. 34 2 Eqn. 32 Eqn. 33) 

2 T. C. 2 V C0 2 = kX + k'Y (Simplifying Eqn. 36) 

(37) 
V = X + Y (Simplifying Eqn. 32) . . ^ . (38) 

From equations 37 and 38 the values of X and Y can be de- 
termined when k and k' are known. 

Gaseous Hydrocarbons and Nitrogen 

If nitrogen is present with the gaseous hydrocarbons, the 
total contraction on combustion (see p. 128) is equal to the sum 
of the volume of the mixture and the volume of the necessary 



THE COMBUSTION OF GASES 137 

oxygen, less the sum of the volume of carbon dioxide formed 
and the volume of nitrogen present, or 

T. C. = V + 2 C0 2 - N 2 . > ..' , . ( 39 ) 

where N 2 represents the volume of nitrogen in the gas mixture. 
The introduction of the unknown, N 2 , in the preceding equa- 
tion renders the four equations between the four determinable 
factors and the unknowns independent when the hydrocar- 
bons are not all of the same group (Second and Third Cases) 
and gives three independent equations when the hydrocarbons 
are all of the same group (First Case). Thus it is seen that the 
presence of nitrogen in a mixture that is otherwise composed 
entirely of hydrocarbons increases the number of independent 
equations by one and thereby provides for its own determina- 
tion. In general, the determinability of any hydrocarbon mix- 
ture is not affected by the presence of an unknown amount of 
nitrogen. 

This also holds true if the nitrogen be replaced by ammonia, 
or nitrous oxide, or hydrogen cyanide, if the necessary changes 
are made in the expressions involving 0%, CO2, and T. C. 

Summary 

1. More than three gaseous hydrocarbons cannot be deter- 
mined by one complete combustion. 

2. Two gaseous hydrocarbons of known composition and of 
the same group can always be determined by one complete 
combustion. 

3. Three gaseous hydrocarbons of known composition, two 
of which belong to the same group, can always be determined 
by one complete combustion. 

4. Three gaseous hydrocarbons of known composition, but 
which belong to different groups, can usually be determined by 
one complete combustion (note exceptions). 

5. In a mixture of hydrocarbons of two groups, the percent- 



138 GAS ANALYSIS 

age of each group can be determined by one complete combus- 
tion. 

6. Any of the mixtures that have been mentioned above is 
still determinable even if an unknown quantity of nitrogen 
is present. 

IDENTIFICATION OF GASEOUS HYDROCARBONS 

To identify a gaseous hydrocarbon or to determine the rel- 
ative amounts of carbon and hydrogen in a mixture of hydro- 
carbons, it is necessary only to burn a measured volume of the 
gas with oxygen and to determine the total contraction and the 
carbon dioxide formed. From these data the calculation may 
be made as follows: 

CnHm + (n + -) O 2 = nCO 2 + H 2 O 
and if V = the volume of the gas sample 

V CnHm + V (n + -) O 2 = V nCO 2 4- V - H 2 O . 

4 2 

Since the total contraction, T. C. = V + O 2 CO 2 (see 
p. 1 28) then, in the present case, 

T. C. = V + Vn + V m Vn or 
4 

T. C. = V + V- and 

4 

4 (T. C. - V) 



m 



V 

Since CO 2 = Vn 
C0 2 

^T 

In the determination of inflammable gases by combus- 
tion over mercury, it should be borne in mind that, if great ac- 
curacy is desired, correction must be introduced for the varia- 



THE COMBUSTION OF GASES 139 

tion of the actual molecular volumes of certain gases from the 
molecular volumes calculated for these gases on the basis of 
Avogadro's hypothesis. The gram-molecular volume of a gas, 
that is, the volume, under standard conditions, occupied by 
the molecular weight of a gas in grams, is nearly the same in 
all cases, namely 22.4 liters. Yet the gases with which we 
chiefly have to do in combustion analysis show slight variations 
from this mean, and in one case, that of carbon dioxide, the dif- 
ference is considerable. 





M 


DH20 = I 


M 
D 


Mol.-VoI. 
Oxygen = i 


H 2 


2.016 


o . 00008988 , 


22.43 


I .0017 


2 


32.00 


O.OOI429I 


22.39 


I .0000 


CO 


28 . 003 


O.OOI2507 


22.39 


I . OOOO 


CH 4 


16.035 


0.0071464 


22.44 


I .0020 


C0 2 


44.003 


O.OOI977 


22. 26 


0-99393 



In the gas volumetric comparison of hydrogen, oxygen, carbon 
monoxide and methane, the variations from one another do not 
amount to more than 0.2 per cent as will be seen from the figures 
in the last column of the table, where the molecular volumes 
are calculated on the basis of that of oxygen as unity. But, as 
Wohl has pointed out, 1 when gases that contain carbon are 
burned, an error too great to be disregarded in exact work will 
result if correction is not introduced for the low molecular vol- 
ume of carbon dioxide. The molecular volume of CO2 is 99.4 
per cent that of CO. Consequently when CO is burned, the gas 
volume changes are accurately represented not by the usual 
equation 

2 CO + O 2 = 2 CO 2 

2 VOl. I VOl. 2 VOl. 

but by the following: 

2 CO + O 2 = 2 CO 2 

2 VOl. I VOl. 2 X .994 = 1.988 VOl. 
1 Ber. d. deutsch. chem. Ges., 37 (1904), 429. 



140 GAS ANALYSIS 

If then the CO is calculated directly from the contraction, the 
result will be 1.2 per cent of the true volume of CO too high. 
Similarly if the CO is determined by absorption of the CO2 
formed, the result will be 0.6 per cent of the true volume of CO 
too low. For further details and for the statement of the slight 
corrections to be introduced in the determination of H2 and CH4 
by combustion, the reader is referred to the article by Wohl. 1 

1 Loc. dt. 



CHAPTER XII 
THE DETERMINATION OF GASES BY COMBUSTION 

ANALYSIS BY EXPLOSION 

The Explosion Pipette for Technical Gas Analysis (Fig. 69). 
This consists of the thick-walled explosion-bulb A and the 
level-bulb B, which are joined together by a piece of enamelled 




FIG. 69 

rubber tubing T. The explosion bulb is supported by Plaster 
of Paris P as shown in the figure. At C two fine platinum wires 
are fused into the explosion pipette, the ends of the wires being 
about 2 mm. apart. At D is a glass stopcock, and the pipette 
terminates in the capillary K, whose end is closed by a short 
piece of rubber tubing 5 and a stout pinchcock. 

141 



142 GAS ANALYSIS 

The gas mixture that is to be exploded is introduced into the 
bulb A, the gas is brought approximately to atmospheric pres- 
sure, and the glass stopcock D is closed. The rubber tube 5 is 
next closed by the pinchcock, and a piece of glass rod is slipped 
into the end of the rubber tube. The pipette is then vigorously 
shaken to insure full mixture of the gases, the terminals at C are 
connected with the poles of an induction coil, a screen of plate 
glass is placed in front of the pipette and the current is turned 
on. The stopcock D is now opened at once, and the gas in the 
pipette is transferred without delay to the burette, and is meas- 
ured at once if the burette is filled with mercury, or after one 
minute if the burette contains water. 

In general, the pipettes and burettes for technical gas analysis 
are filled with aqueous solutions, but the explosion pipette is 
filled with mercury. By using mercury as confining liquid 
during the explosion it is possible afterward to determine the 
carbon dioxide formed in the combustion. If the explosion is 
made over water, a subsequent measuring of the carbon dioxide 
formed is inadmissible, because the pressure in the pipette is 
so high during the explosion that considerable quantities of 
carbon dioxide are absorbed by the water. By exploding over 
mercury very satisfactory results are obtained, even if the car- 
bon dioxide is afterward measured in a burette that contains 
water as the confining liquid. 

If the explosion is too violent it is possible that some oxides 
of nitrogen may be formed, if nitrogen is present. On the other 
hand, if the combustion in the pipette proceeds too slowly, the 
oxidation of the gases is probably not complete. The closing 
of the capillary of the explosion pipette in the manner above 
described furnishes not only a sort of safety-valve, for the re- 
lease of pressure if the explosion is too violent, but also affords 
means of judging the energy of the explosion. If the explosion 
has the proper intensity, there will be a quick jerk of the rubber 
tube at the moment of explosion, but both pinchcock and glass 
plug will remain in place. With too violent an explosion, the 



DETERMINATION OF GASES BY COMBUSTION 143 

pinchcock is forced open, and the glass plug is driven out of the 
rubber tube. If the combustion is not sufficiently vigorous, no 
movement of the rubber tube is seen. From these statements 
it is apparent that the suggestion to modify the Hempel ex- 
plosion pipette by placing a glass stopcock at the upper end of 
the capillary K, not merely exposes the operator to the 
danger of accident through the bursting of the pipette, but 
also deprives him of a means of judging the intensity of the 
explosion. . 

Proportion of Gases in Analysis by Explosion. Bunsen 
found that 

100 vol. of airwith 13.45 oxyhydrogen gas would not burn. 

Vol. of Air 
remaining 

100 air burned with 26.26 oxyhydrogen gas, left 100.02 



100 34.66 

100 " 43.72 

zoo " " 51.12 

loo " " 64.31 

ioo " " 78.76 

100 " " 97.84 

ioo " " 226.04 



100.15 
100.07 

99.98 
99.90 

99-43 
96.92 

88.56 



These results led Bunsen to recommend that in the determina- 
tion of hydrogen by explosion not less than 26 volumes nor 
more than 64 volumes of combustible gas be used to ioo vol- 
umes of incombustible gas. It should, however, be borne in 
mind that the above proportions refer only to the explosion of 
mixtures of hydrogen and oxygen. With combustible gases 
other than hydrogen quite different ratios should be used. This 
is evidenced by the results of Teclu 1 who finds that mixtures of 
hydrogen, methane, acetylene and illuminating gas are explosive 
only when the amount of the combustible gas lies between the 
following percentage volumes : 

1 Jour, fur praktische Chemie, 75 (1907), 212. See also Burrell, /. Ind. Eng. 
Chem. 5 (1913), 181. 



144 GAS ANALYSIS 

Hydrogen, 10 to 63 per cent 
Methane, 3.5 " 7.9 
Acetylene, 1.6 " 5.8 
Illuminat- 
ing Gas 4.5 " 23.5 

Formation of Oxides of Nitrogen. It was long supposed 
that if the explosion of gas mixtures was made under the con- 
ditions that Bunsen laid down, the formation of oxides of ni- 
trogen would always be avoided. Experimental evidence now 
seems to show that, when nitrogen is present, oxides of nitro- 
gen are produced in varying amounts and that the quantity 
may at times be so appreciable as to introduce a considerable 
error in the results of analysis. A further source of possible 
error in the determination of hydrogen by explosion has been 
pointed out by Misteli l who states that small amounts of hy- 
drogen escape combustion. 

Induction Coil. For producing the spark for the explosion 
an induction coil giving a spark about 15 mm. long will be found 
adequate. The current for operating this coil may be obtained 
from either dry or wet cells or from a storage battery or from 
a dynamo with sufficient resistance in the circuit. 

The Hydrogen Pipette. If a gas mixture contains so small 
an amount of combustible gas that it will not explode when 
mixed with oxygen or air, pure hydrogen or oxyhydrogen gas 
is added to the mixture. For the preparation of hydrogen gas 
for this purpose the hydrogen pipette (Fig. 70) may be used. 
This is a simple absorption pipette that has two small bulbs 
in the place of the first large bulb. Through the tube g a glass 
rod h is pushed up to the mouth of e. This rod is fastened 
tightly into g by means of a piece of rubber tube slipped over 
it, and it serves to hold pieces of chemically pure zinc in the 
bulb e. To fill the pipette it is inverted, the glass rod is taken 
out, and the pieces of zinc are dropped into e. The pipette is 

1 Jour.fUr Gasbdeuchtung, 48 (1905), 802. 



DETERMINATION OF GASES BY COMBUSTION 145 



then closed again, placed upright, and filled with dilute sul- 
phuric acid (1:10) by means of a funnel. The pipette is closed 
at i with a piece of rubber tubing and a pinchcock. 

After a short time the hydrogen produced will drive back 
the acid, so that the evolution ceases. Before drawing off the 
sample of hydrogen from the pipette it is advisable to drive out 
the gas in the pipette until the 
bulb e is completely filled with 
sulphuric acid. This may be 
done by blowing into a rubber 
tube attached to c. A new sup- 
ply of pure hydrogen is now 
generated, and this gas may be 
used in the analysis. If several 
analyses are made one after 
another, this fresh evolution of 
the gas is unnecessary; but if 
the apparatus has stood for any 
length of time, air will diffuse 
through the sulphuric acid, and 
some oxygen and nitrogen will 
be found in the first portion of 
hydrogen that is drawn off. To 
obtain a more active evolution 
of hydrogen than that which 
takes place when pure zinc and 
pure acid are used, a few pieces 
of platinum foil may be put in with the zinc. 

Oxyhydrogen Gas Generator. Oxyhydrogen gas may con- 
veniently be generated in the apparatus of Hempel (Fig. 71), 
which is patterned after that described by Bunsen. 1 It consists 
of a glass cylinder into which there is inserted a cylindrical ves- 
sel a which is held in place by a cork fitting into the neck of 
the outer cylinder. The terminals / are platinum plates sus- 

1 Gasometrische Methoden, 26. ed. (1877), 77. 




FIG. 70 



146 



GAS ANALYSIS 



pended on platinum wires that are fused into the sides of a and 
pass upward to the two mercury cups d and e. The outer 
cylinder is filled with water and the inner cylinder with dilute 
sulphuric acid (1:10). Into the neck of the inner cylinder a 
there is ground a glass tube that carries the bulb c and ter- 
minates in the bent capillary tube b. In the generation of 
oxyhydrogen gas by the electrolysis of acidulated water some 

ozone is always formed and this 
gas on being brought into the 
explosion pipette would unite with 
the mercury. This would cause a 
small excess of hydrogen in the 
oxyhydrogen gas. The ozone that 
is formed during the electrolysis 
may be converted into oxygen by 
exposing the oxyhydrogen gas, be- 
fore using it, to the action of dif- 
fused daylight for twelve hours. 
It is to hasten this change that the 
bulb c of about 50 cc. capacity is 
placed between the generator and 
the capillary tube b. To prepare a 
sample of oxyhydrogen gas for use 
in explosion analysis, d and e are 
connected with a suitable source of 
current and oxyhydrogen gas is 
rapidly generated for about i}4 
hours. A little mercury is then 
introduced into the open end of 
b and the generator is allowed to stand in the light for 
twelve hours. 

The Explosion Pipette for the Hempel Apparatus for 
Exact Analysis (Fig. 72). In the exact analysis also it is most 
convenient to make the explosions in a pipette specially con- 
structed for the purpose. This pipette differs from the ordinary 




FIG. 71 



DETERMINATION OF GASES BY COMBUSTION 



147 



pipettes only in having a stopcock at a and two platinum wires 
fused in at b. 

To burn a gas mixture in this apparatus, the gas is brought 
into it in the usual manner, the stopcock is closed, and a fine 
sewing needle is placed in the mouth of the capillary c. Upon 
connecting the platinum wires with an induction apparatus, 
the mixture is exploded by the spark which passes when the 
circuit is closed. 





FIG. 72 FIG. 73 

Hydrogen for use in explosions in the Hempel exact analysis 
may be made in the pipette shown in Fig. 73. 

The construction of this pipette resembles that of the hydro- 
gen pipette shown and described on page 145. 

ANALYSIS BY COMBUSTION 

Combustion with an Electrically Heated Platinum Spiral 

The Combustion Pipette. Coquillion was the first to pro- 
pose the use of the glowing platinum spiral in the determination 
of such gases as marsh-gas and hydrogen. Winkler improved 
the form of the apparatus and used a Hempel pipette for solid 



148 



GAS ANALYSIS 



and liquid reagents. While adhering in the main to the Winkler 
arrangement, the author has modified the apparatus so that 
mercury may be used as the confining liquid. This permits 
of a much more accurate determination of carbon monoxide 
or hydrocarbons than is possible over water. The cylin- 
drical portion of a Hempel simple pipette for solid and 
liquid reagents, A, Fig. 74, is fastened to the stand in the 
usual manner, except that the bulb is supported by a small 




FIG. 74 

block of Plaster of Paris, P. In the neck of the pipette is in- 
serted a two-hole rubber stopper S through the openings of which 
glass tubes cc pass from below the stopper to within about 
20 mm. of the top of the pipette. Inside of each glass tube is a 
stout iron wire 2.5 mm. in diameter which reaches nearly to the 
top of the glass tube and projects about 10 mm. below the lower 
end. To the lower end of each iron wire there is attached a 
small binding post and the connection between the glass tube 
and the binding post is made air-tight by slipping over the 



DETERMINATION OF GASES BY COMBUSTION 149 

ends of each a short piece of rubber tubing R which is then se- 
curely wired in place. Small iron screws are threaded into open- 
ings in the upper ends of the two iron wires, and serve to hold in 
place the ends of the platinum spiral W. A strip of iron about 
one cm. wide is bent in the form of an S around the two glass 
tubes about midway up in the bulb of the pipette for the pur- 
pose of holding the tubes more rigidly in position. The platinum 
spiral that connects the upper ends of the two iron wires is made 
of platinum wire J^ mm. in diameter which is bent in a coil 
about 2 mm. in diameter and contains from 20 to 30 turns. 
The ends of the platinum wire are fastened under the two 
small screws in the upper ends of the iron wires. The two 
binding posts that are fastened to the lower ends of the iron 
wires are connected to two larger binding posts M fastened 
into a plate of hard rubber that is itself attached to the base 
of the iron frame. The combustion pipette is usually filled with 
mercury which is introduced through a small funnel inserted 
in the tube of the level-bulb B. After the pipette has been filled 
with the mercury, the air that may be trapped by the mercury 
in the glass tubes surrounding the iron wires is removed by 
closing the capillary tube of the pipette with a piece of rubber 
tube and pinchcock and attaching a water suction pump to 
the tube of the level-bulb. 

When the pipette is constructed and is filled with mercury 
in the manner above described, the iron wires passing through 
the glass tubes do not come into contact with the gas mixture 
in the pipette at any point, for when a gas is passed into the 
pipette the glass tubes remain filled with mercury which covers 
the ends of the iron wires. This makes it entirely unnecessary 
to use heavy platinum wires in the place of the iron wires as 
has been recommended by Porter and Ovitz. 1 

Manipulation of the Combustion Pipette. In carrying 
out a combustion with this pipette a measured amount of oxygen 
(about 100 cc.) is passed into it from a gas burette and the gas 

1 Bulletin i, Department of the Interior, Bureau of Mines, 1910, p. 24. 



150 GAS ANALYSIS 

to be burned is then measured off in the burette. Ordinarily 
the total unabsorbable residue from a gas sample of about 
100 cc. is used in the combustion, but the volume of the 
sample taken should be of such size that after combustion 
an excess of oxygen remains in the pipette. The gas bu- 
rette H is connected with the combustion pipette by the usual 
bent capillary tube, and the wires from the source of current 
are fastened to the binding posts on the frame of the pipette, 
Fig. 75. A small rheostat R is introduced into the circuit to per- 
mit of ready control of the current flowing through the platinum 
spiral and thus to enable the operator to keep the spiral at dull 
redness throughout the combustion. The current for heating 
the spiral may be that from a storage battery or from a dynamo, 
or more conveniently the alternating current of a lighting cir- 
cuit. If the alternating current is employed, the connections 
may be made as shown in the figure. A plug carrying two wires 
is screwed into an ordinary lamp socket; one of the wires is con- 
nected with the rheostat and the other with a bank of lamps L 
connected in parallel. The further terminal of the lamps is 
connected with one of the binding posts M on the pipette, and 
the other binding post is connected with the rheostat R. The 
coarser adjustment of the current is made by means of the lamps 
and the finer adjustment by means of the rheostat. 

Different gases show great differences in heat conductivity 
and if adjustment of the current were not easily possible 
the spiral might be raised to so high a temperature during the 
process as to melt the platinum wire. For example, when hy- 
drogen is burned in the pipette by first introducing that gas 
and then admitting a mixture of air and oxygen, a current that 
will at the beginning heat the spiral only to redness in the at- 
mosphere of hydrogen will bring the platinum wire to a bright 
yellow glow and will at times melt it in the mixture of nitrogen 
and oxygen that remains after the hydrogen has been burned. 
After the combustible gas has been introduced, the platinum 
spiral is kept at dull redness for 60 seconds. The current is then 



DETERMINATION OF GASES BY COMBUSTION 151 




FIG. 75 



152 GAS ANALYSIS 

turned off, the pipette is allowed to cool, and the gas residue is 
passed back into the burette and measured. Air or a mixture 
of oxygen and air may be used in the pipette in place of pure 
oxygen. If the combustible gas contains acetylene or its homo- 
logues it should be run into the pipette very slowly and under 
a pressure that is only very slightly above that of the prevailing 
atmospheric pressure. If this precaution is not taken, dissocia- 
tion is liable to occur when the gas comes in contact with the 
hot spiral, and the separated carbon would of course then escape 
combustion. 

In most cases the process may be reversed and the combustible 
gas be first introduced into the pipette, and oxygen or air or a 
mixture of the two then passed in from the burette. This ma- 
nipulation is, however, not suited to the combustion of acety- 
lene because the hot spiral causes decomposition of this gas 
with the deposition of solid carbon. 

The chief merits of this method of combustion are: 

(1) The use of a large volume of combustible gas with con- 
sequent increase in the accuracy of the results; 

(2) The avoidance of explosion by the gradual addition of 
oxygen to the combustible gas or of the combustible gas to 
oxygen; 

(3) The avoidance of the formation of measurable amounts 
of the oxides of nitrogen in the combustion of gas mixtures that 
contain nitrogen. 

Formation of Oxides of Nitrogen in Combustion Pipette. 
A. H. White has described experiments 1 that lead him to 
state that oxides of nitrogen are formed when hydrogen is burned 
with oxygen and air in this pipette, and he bases this statement 
upon the fact that he obtained a reaction for nitrites with 
Griess's reagent after heating air alone in the combustion pip- 
ette, and further that there was contraction in volume when the 
products of the combustion of hydrogen with oxygen and air 
were passed into a pipette containing potassium hydroxide. 

1 Jour. Am. Chem, Soc., 23 (1901), 476. 



DETERMINATION OF GASES BY COMBUSTION 153 

F. H. Rhodes has, at the request of the author, carefully re- 
peated and extended the experiments of White, and he finds 
that no measurable amount of oxides of nitrogen is formed when 
the conditions that were given in the original article of Dennis 
and Hopkins 1 are followed, and the platinum spiral is heated 
only to dull redness during the combustion and is kept at dull 
redness for no longer than sixty seconds after the gases have 
been introduced into the pipette. Upon passing air that has 
been heated in this manner in the pipette through 5 cc. of an 
8% solution of pure sodium hydroxide, acidifying this with 
acetic acid and adding i cc. of Griess's reagent, there resulted 
a color which, on comparison with a nitrite solution of known 
strength, showed that not more than a trace of oxides of nitro- 
gen was produced under these conditions. When the spiral was 
heated tor five minutes to a temperature of dull redness in 100 cc. 
of air, the colorimetric determination of the nitrite that was 
formed showed that the amount of the oxides of nitrogen pro- 
duced did not in any case exceed ^-g- of a cc., and that the vol- 
ume is usually much less than this. When the temperature of 
the spiral was raised beyond a dull red heat, the amount of the 
oxides of nitrogen that was formed increased with rise of tem- 
perature, but the total amount of the product even after heat- 
ing the air for five minutes with the spiral at a bright yellow 
was not measurable in a Hempel burette over mercury. 

In the combustion of hydrogen with a mixture of oxygen 
and air, Rhodes found that when the spiral is properly heated, 
the amount of oxides of nitrogen that was produced is slightly 
higher than when air alone is heated, but that the volume of 
this product was in no case large enough' to permit of its volu- 
metric measurement when 100 cc. of hydrogen was burned. 
To ascertain whether an appreciable error would result in the 
combustion of hydrogen with a mixture of air and oxygen when 
the spiral was highly heated, 100 cc. of hydrogen was introduced 
into the pipette, the spiral was heated to bright yellow, and 
1 Jour. Am. Chem. Soc. t 21 (1899), 398. 



154 GAS ANALYSIS 

100 cc. of a mixture of equal volumes of air and oxygen was 
slowly passed in. The colorimetric determination of the amount 
of nitrite formed when the products were passed into the so- 
dium hydroxide showed that even under these unusual condi- 
tions, the volume of the oxides of nitrogen that was formed 
was less than pjir f a cc -> an error that is entirely negligible in 
technical gas analysis when working with a gas sample of 100 cc. 
In the analysis of gas mixtures that commonly occur in techni- 
cal practice, the error would be very much less than that above 
cited because of the lower percentage of hydrogen. As a fur- 
ther check upon the above results a mixture of i cc. of nitrogen 
tetroxide and 99 cc. of air was made in a Hempel burette over 
mercury. 99 cc. of this mixture was then driven out of the bu- 
rette and the residual i cc. of gas was diluted with a further 
99 cc. of air. This total gas volume, now containing o.oi per 
cent of nitrogen tetroxide, was passed through a solution of 
sodium hydroxide. The solution was acidified with acetic acid 
and Griess's reagent was then added. The depth of color of this 
solution was found to be much greater than that resulting from 
a similar treatment of the gases produced by the different meth- 
ods of combustion described above, and this held true even 
when the hydrogen was burned under conditions most favor- 
able to the formation of oxides of nitrogen, namely, high tem- 
perature of the spiral and slow introduction of the gas. 

Combustion with a Platinum Capillary Tube (Drehschmidf) 

The determination of combustible gases by explosion or by 
combustion in the combustion pipette necessitates the employ- 
ment of an electric current. With the apparatus devised by 
Drehschmidt 1 the combustible gases mixed either with air or 
with pure oxygen may be burned without danger of explosion 
in a platinum capillary tube that is heated to the requisite 
temperature by means of a gas flame. In the original form 

1 Berichte d. deutsch. chem. Ges., 21 (1888), 3242. 



DETERMINATION OF GASES BY COMBUSTION 155 

proposed by Drehschmidt the platinum combustion tube was 
given a length of 200 mm. to prevent the ends of the tube from 
becoming too warm. Winkler improved the device by fitting 
a water jacket to each end of the tube which rendered it possible 
to reduce the platinum tube to a length of 100 mm. The Winkler 
form of tube is shown in Fig. 76. The combustion tube P is 
of platinum and has a length of 100 mm., an external diameter 



W 




FIG. 76 

of 2.5 to 3 mm. and an internal diameter of 0.7 mm. The tube 
should not be lap-welded but should be bored or drawn. Inas- 
much as an explosive gas mixture is passed through the tube 
from the gas burette, it is necessary to prevent the propaga- 
tion of the combustion from the tube to the gas mixture in the 
burette. This is accomplished by filling the platinum tube 
with fine platinum wires. The ends of the combustion tube are 
soldered to copper tubes CC that have an external diameter 



156 GAS ANALYSIS 

of about 3.5 mm. and an internal diameter of 1.5 mm. These 
tubes are bent at right angles as shown in the figure and their 
horizontal portions are also filled with fine platinum wires. 
The water jackets, WW, are of sheet brass and are about 5 cm. 
long and 2.5 cm. wide. They are fastened upon the tube in 
such position that the junctions of the platinum and copper 
lie within the water coolers. Each jacket has an opening in 
the top for the introduction of cold water. 

Before being put in use the combustion tube should be care- 
fully tested to ascertain whether it is tight. This may be done 
by connecting a glass tube about 20 cm. long to one of the cop- 
per tubes, immersing the lower end of the glass tube in mercury, 
joining the other copper tube to a water suction pump by 
means of a piece of rubber tubing and drawing up the mercury 
in the glass tube to a height of about 10 cm. The rubber tube 
is then closed by a pinchcock. If the tube does not leak the 
mercury in the glass tube will not fall. If the tube is found to 
be tight at ordinary temperatures, the pinchcock is opened, the 
platinum tube is heated by a Bunsen flame and the test is then 
repeated. In the experience of the author the chief objection 
to the Drehschmidt tubes that are now on the market lies in 
the fact that they begin to leak after having been in use only a 
comparatively short time. This constitutes a serious drawback 
when the high cost of the tube and the difficulty of repairing 
it in the laboratory are taken into consideration. 

In carrying out a combustion with this apparatus the meas- 
ured sample of gas to be burned is passed over into the simple 
gas pipette H, and an amount of air or oxygen that is surely 
sufficient to burn the combustible constituents of the gas mixture 
is measured off in the gas burette. This is then passed into 
the pipette and the pinchcock at the top of the pipette is closed. 
The Drehschmidt tube is then placed in position as shown in 
the figure, the burette being of course filled to the top with the 
confining liquid. The platinum combustion tube P is heated 
to bright redness by means of the burner B, the pinchcocks on 



DETERMINATION OF GASES BY COMBUSTION 157 

the pipette and burette are then opened and the gas is slowly 
drawn over into the burette. Two passages of the gas through 
the capillary suffice for complete combustion. The platinum 
tube is then allowed to cool and the residual gas is drawn into 
the burette and measured. The simple pipette is now replaced 
by a pipette containing potassium hydroxide, and the carbon 
dioxide is removed and the gas residue is again measured. If 
hydrogen and methane are being simultaneously determined, 
results of only approximate accuracy are obtainable when water 
is used as the confining liquid in the burette and pipette. In 
such case it is therefore preferable to use a pipette with level- 
bulb (see Fig. 51) and to employ mercury as the confining 
liquid in both the pipette and the burette. 



CHAPTER 



PROPERTIES OF THE VARIOUS GASES AND METHODS 
FOR THEIR DETERMINATION 

OXYGEN 

Properties of Oxygen. Specific gravity, 1.1055 *; weight 
of one liter, 1.4292 gram; critical temperature, 118; critical 
pressure, 50 atmospheres. 

Oxygen is but slightly soluble in water. One liter of water 
absorbs, from atmospheric air, according to L. W. Winkler, 2 
Otto Pettersson, and K. Sonden, 3 at 760 mm. pressure: 

at o C. 10.01 cc. 

6 C. 8.3 

" 9.18 C. 7.9 

"14.1 C. 7.05 

" 16.87 C. 6.84 

" 23.64 C. 5-99 " 

" 24.24 C. 5.916 " 



and of pure oxygen, according to Bunsen 
at 20 C., 28.38 cc. 

One volume of alcohol absorbs, according to Carius, at all 
temperatures between o and 24, 0.28397 volume. 

Determination of Oxygen. Oxygen may be determined 
either by mixing it with an excess of hydrogen and exploding 

1 Most of these figures are from Landolt and Bernstein's Physikalisch-chemische 
T&bellen. 

z Berichte der deutschen chemiscken Gesellschaft, 21 (1888), 2843. 
3 Ibid., 22 (1889), 1443. 

158 



PROPERTIES OF THE VARIOUS GASES 159 

the mixture, or by passing the gas into a combustion pipette 
containing an excess of hydrogen, or by bringing it into con- 
tact with glowing metallic copper, or by absorption of the gas. 

Determination of Oxygen by Combustion. The explosion 
analysis may be carried out in the apparatus described on 
page 141. 

The combustion may most conveniently be performed in the 
pipette shown in Fig. 74. 

In either of these methods two volumes of hydrogen unite 
with one volume of oxygen to form liquid water. The volume 
of oxygen present is consequently equal to */3 of the contraction 
of the gas volume. 

The hydrogen needed for these analyses may be prepared 
in the hydrogen pipette (Fig. 70) or it may be generated by 
the electrolysis of water in the Bunsen apparatus, 1 in which 
the positive pole consists of a zinc wire floating in mercury. 
In the determination of oxygen by explosion with hydrogen, 
the oxygen should be mixed with from three to ten times its 
volume of hydrogen. If the amount of oxygen in the original 
gas mixture is quite low, there should be added, in addition to 
the hydrogen, an amount of oxyhydrogen gas sufficient to render 
the mixture explosive. 

Determination of Oxygen with Copper Eudiometer. Very 
accurate determinations of oxygen may be made by combus- 
tion with copper. U. G. Kreusler has so improved the ap- 
paratus devised by Ph. v. Jolly for the determination of oxygen 
in the atmosphere that it is now one of the most exact methods 
known. A so-called copper eudiometer, whose construction is 
based upon his well-known air thermometer, is used for the 
determination. The air whose oxygen contents is to be deter- 
mined is admitted into a bulb that has previously been com- 
pletely exhausted, and the pressure is read off on a very exact 
mercury manometer. The oxygen is then absorbed by a copper 
spiral that is heated to glowing by a strong electric current; 

1 Gasometrische Methoden, ad ed. (1877), p. 80. 



160 GAS ANALYSIS 

the metallic copper is changed to cuprous and cupric oxide. 
After the apparatus has become cool, the remaining nitrogen 
is brought to the initial volume by changing the pressure, 
and a reading is taken of the pressure now prevailing. 1 
When due regard is given to all the necessary precautions, the 
method is of the greatest exactness; it is, however, very complex 
and tedious, and for this reason is not well suited to the making 
of a large number of determinations. 

Determination of Oxygen by Absorption. Oxygen may 
rapidly and accurately be determined by means of various ab- 
sorbents, among the best of which are 

1. A strongly alkaline solution of pyrogallol, 

2. Phosphorus in solid form, 

3. Phosphorus in solution, 

4. Metallic copper, 

5. Solutions of ferrous salts, 

6. Sodium hyposulphite, 

7. Chromous chloride. 

i. Alkaline Pyrogallol 

Hempel prepares the alkaline solution of pyrogallol by dis- 
solving 120 grams of potassium hydroxide not purified by alco- 
hol in 80 cc. of water and adding to this 5 grams of pyrogallol 
dissolved in 15 cc. of water. The two solutions are brought 
together in a double absorption pipette (Fig. 36) or in the ap- 
paratus described on page 161. Hempel states that a solution 
prepared as above gives off no carbon monoxide during the ab- 
sorption, or at most only such slight amounts that the error 
thus caused falls within the limit of the error of the readings. 
Benedict, 2 however, appears to be of the opinion that the re- 
agent thus prepared will set free some carbon monoxide although 

1 U. Kreusler, Ueber den Sauerstojfgehcdt der atmospharischen Luft. Landwirth- 
schaftliche Jahrbiicher, 1885, p. 305. 

2 The Composition of the Atmosphere, Publication No. 166 of the Carnegie Institu- 
tion of Washington, 1912, p. 113. 



PROPERTIES OF THE VARIOUS GASES 161 

if 

he gives no experimental proof that it does so. He recommends 
that the absorbent be prepared as follows: 500 grams of stick 
potassium hydroxide, not purified by alcohol, is dissolved in 
250 cc. of water. The specific gravity of the solution is usually 
1.55, but, if it varies materially from this figure, more potas- 
sium hydroxide or more water is added until the density of 
1.55 is reached. 135 cc. of this solution is added to a solution 
of 15 grams of pyrogallol in 15 cc. of distilled water. 

The determination should not be made at a temperature 
much below 15, for the absorption by alkaline pyrogallol is 
very much less active at a temperature under 7. At a tem- 
perature of 15 or higher, the last trace of oxygen can be re- 
moved with certainty in the space of three minutes by shaking 
with the solution of alkaline pyrogallol, while at lower tempera- 
tures the absorption is not complete after six minutes. The 
analytical absorbing power of the solution is from 2 to 2}^. 

If a large number of oxygen determinations is to be made 
by the "exact" method, the reagent is kept in the apparatus 
shown in Fig. 77. With this device a large quantity of the 
reagent may be stored, measured off, and transferred to the 
absorption pipettes without coming in contact with the air. 

The large reservoir bulb A ends above in the U-shaped tube .5, 
which has a short side-arm at/ and ends in the h shaped capil- 
lary g. To the lower side of 'the bulb is attached the bent tube h, 
which is provided with a glass stopcock i. A small funnel can 
be fastened to the upper end of h by a rubber tube k. A thin 
rubber tube connects the side-arm / with the funnel o. The 
ends of the I capillary g are provided with short pieces of rub- 
ber tubing and with pinchcocks. The apparatus is first filled 
completely with mercury. A funnel or glass tube is then in- 
serted in the free end of m, the pinchcocks n and y are closed, 
the stopcock i is opened, and the aqueous solution of pyrogallol 
is poured into the funnel attached to m. The end k of the tube h 
is now connected by a rubber tube with a suction flask, and the 
flask is joined to an aspirator. Upon opening the pinchcock 



l62 



GAS ANALYSIS 



at m the mercury flows through h into the flask, and the solu- 
tion of pyrogallol is drawn into A . The entrance of the reagent 
can instantly be stopped by turning the stopcock i. When all 
of the pyrogallol has entered the pipette, the solution of potas- 




FIG. 77 

sium hydroxide is poured into the funnel and drawn in in the 
same manner. The two solutions in the apparatus are then 
thoroughly mixed by shaking. 

To transfer some of the reagent to a pipette, the apparatus 
is arranged as shown in Fig. 77. The capillary of the pipette 



PROPERTIES OF THE VARIOUS GASES 163 

is inserted at y into the end of the rubber tube attached to the 
lower end of g. By blowing into I (this can best be done with the 
rubber pump, Fig. 8) the mercury in the pipette is driven to g, 
and m, n, and y are then closed. Some mercury is poured into 
the funnel inserted in k, and i is opened. Upon lowering the 
funnel o and opening the pinchcock n, the left side of the U- 
shaped tube B can easily be filled down to a mark with the re- 
agent, for the mercury drives the reagent out of the bulb into B. 
When the reagent has thus been measured off, i is closed, y is 
opened, and by raising the funnel o the reagent is driven over 
into the pipette until the mercury reaches the point x. The 
pipette is then disconnected, the capillary d is immersed in a 
beaker of distilled water, and by careful alternate sucking and 
blowing at / the capillary is freed within and without from the 
last traces of the reagent. It is then dried with filter paper, and 
the pipette is ready for use. 

2. Solid Phosphorus 

The method of Lindemann for the absorption of oxygen by 
solid phosphorus gives, under proper conditions and in the ab- 
sence of gases that inhibit the reaction, very accurate results. 
The amount of phosphorus contained in a Hempel gas pipette 
is capable of absorbing a very large volume of oxygen, in which 
respect it is superior to alkaline pyrogallol which has a rela- 
tively small absorbing power. 

Phosphorus does not, however, unite with oxygen when the 
gas has a high partial pressure. If the oxygen is nearly pure, 
no reaction takes place between it and phosphorus, and only 
when its pressure is lowered either by dilution with another 
gas, or by partial exhaustion with an air-pump, does a union 
of the phosphorus and oxygen result. The reaction between 
the two elements is explosive in character when the gas mixture 
contains from 50 to 75 per cent of oxygen, but it proceeds quietly 
when less than 50 per cent of oxygen is present. It is unsafe 



164 GAS ANALYSIS 

to use the method for the determination of oxygen in gas mix- 
tures that contain enough hydrogen to render them explosive, 
because the rise of temperature caused by the interaction of 
the phosphorus and oxygen may ignite the mixture. In such 
case, or when the mixture contains over 50 per cent of oxygen, 
the gas should be absorbed by some agent other than phos- 
phorus. 

The union of phosphorus with oxygen is prevented or greatly 
retarded by the presence of even small amounts of certain other 
gases, such as ethylene, acetylene, some other hydrocarbons, 
some ethereal oils, alcohol or ammonia. 

The reaction is further dependent upon the temperature. 
It proceeds normally at about 20 C., while at 14 it takes place 
quite slowly, so that a quarter of an hour or longer is required 
to completely separate the oxygen from 100 cc. of air. At 10 
and still lower temperatures a half hour's time would not be 
sufficient. It follows from this that during the colder months 
of the year the absorption must be carried out in warm 
rooms. 

The absorption of oxygen by phosphorus may conveniently 
be effected by passing the gas mixture into a Hempel simple 
pipette for solid and liquid reagents (Fig. 35) that contains 
sticks of phosphorus immersed in water. 

Phosphorus may be purchased on the market in the form of 
thin sticks ready for use, or it may be prepared by the analyst 
himself in this form in the following manner: A test tube is 
filled with water, and sticks of phosphorus of the ordinary 
commercial size are introduced into the tube. The tube is then 
placed in a metal water bath in which the temperature of the 
water is maintained at about 50. The phosphorus readily 
melts and it is protected from the action of the air by the water 
above it. Enough phosphorus should be used to form in the 
test tube a column of molten phosphorus about 7 cm. high. 
A 2-liter beaker full of cold water is placed near the water bath. 
A glass tube with slight taper and about 3 mm. internal diameter 



PROPERTIES OF THE VARIOUS GASES 165 

is then pushed down to the bottom of the test tube containing 
the molten phosphorus, the upper end of the tube is closed with 
the moistened finger, and the tube, carrying a column of the 
molten phosphorus with a little water above it, is quickly lifted 
out of the test tube and dipped into the beaker of cold water. 
If the walls of the glass tube are not too thick, the phosphorus 
soon solidifies and since it decreases in volume on changing from 
the liquid to the solid state the stick will usually fall out of the 
tube of itself. If it adheres to the walls it may easily be pushed 
out with a wire. The cylindrical part of the gas pipette in which 
the phosphorus is to be placed should be of brown glass to pro- 
tect the phosphorus from the action of the light (see p. 56). 
If such pipettes are not available the whole pipette when not 
in use should be covered by a light-tight box of wood or card- 
board. The pipette is filled by turning it upside down, removing 
the stopper of the cylindrical portion, filling the cylinder with 
water, and then introducing the small sticks of phosphorus 
until the cylinder is tightly packed with them. The stopper of 
the cylinder is then inserted and the pipette is turned into up- 
right position. 

In the absorption of oxygen the water in the pipette is first 
driven up in the capillary and to the end of the connecting bent 
capillary tube by blowing into a rubber tube attached to the 
wide tube of the end bulb. The connecting capillary tube is 
then inserted into the rubber tube of the burette and the gas 
mixture is passed over into the phosphorus pipette, the water 
or mercury from the burette being allowed to follow nearly to 
the cylinder of the pipette. The union of the phosphorus 
with the oxygen is complete in three " minutes or less, the 
end of the reaction being shown by the disappearance of the 
glow when the pipette is in a dark room. Inasmuch as the dif- 
ferent oxidation products of phosphorus are soluble in water, 
the surface of the sticks of phosphorus is freed from these sub- 
stances by the solvent action of the confining water provided 
the water is renewed from time to time. 



1 66 GAS ANALYSIS 



3. Phosphorus in Solution 

Centnerszwer has suggested 1 the employment of a solution 
of phosphorus in oil as an absorbent for oxygen in gas analytic 
work. The reagent is prepared by placing about 230 cc. of 
castor oil in a 250 cc. flask, dropping into the oil three 
grams of well dried phosphorus, and after lightly closing the 
neck of the flask with a stopper, heating the contents in an oil 
bath to 200. The hot flask is then removed from the bath, 
the stopper is tightly inserted, and the flask is wrapped in a 
towel and vigorously shaken until complete solution of phos- 
phorus is effected. When cool the solution is ready for use. 
It is introduced into a Hempel double absorption pipette for 
liquid reagents by joining to the wide tube of the pipette, by 
means of a piece of rubber tubing, a wide glass tube bent down- 
ward, allowing this to dip into the oil and drawing the reagent 
into the further bulbs of the pipette by applying suction to 
the capillary tube of the pipette. 

In absorbing oxygen, the gas mixture is passed over into the 
pipette in the usual manner and is allowed to stand in contact 
with the oil solution of phosphorus as long as a glow can be ob- 
served. No harm results if some water happens to pass from 
the burette into the pipette. After the glow in the pipette has 
disappeared, the remaining gas is drawn back into the burette 
and measured. Centnerszwer states that the reagent can be 
used for the determination of oxygen in gas mixtures that are 
high in oxygen, and the confirmatory analyses that he cites 
seem to show that the method is fairly accurate. 

4. Copper 

A very active absorbent for oxygen is metallic copper in the 
form of little rolls of wire-gauze, immersed in a solution of ammo- 
nia and ammonium carbonate. 

1 Chemiker-Zeitung, 34 (1910), 494. 



PROPERTIES OF THE VARIOUS GASES 167 

It has long been known that many metals oxidize readily in 
the presence of vapor of ammonia. The absorption of oxygen, 
however, takes place rapidly only so long as the metallic sur- 
face is bright, and it proceeds very slowly as soon as consider- 
able quantities of oxide are formed. 

A very rapid and complete absorption of oxygen results when 
the gas is brought into contact with metallic copper and a 
solution consisting of equal parts of a saturated solution of com- 
mercial ammonium sesquicarbonate and a solution of ammonia 
of 0.93 specific gravity. Such an ammoniacal solution has a 
tension that may in most cases be disregarded, and, provided 
the absorption apparatus contains sufficient metallic copper, 
the solution can easily absorb 24 times its volume of oxygen. 
Its analytical absorbing power is therefore 6. Since the sur- 
face of metallic copper is frequently covered with a thin layer 
of grease, it is necessary to clean it before using by exposing 
it for a moment to the action of nitric acid. 

The reagent is used in the same manner as solid phos- 
phorus, in a pipette for solid absorbents. In making the 
absorption, the gas is allowed to remain in the pipette for five 
minutes. 

The method described admits of a very rapid and exact de- 
termination of oxygen. As compared with alkaline pyrogallol, 
copper has a much greater absorbing power for oxygen, and it 
has the advantage over phosphorus, aside from the danger at- 
tending the use of the latter, of absorbing equally well at any 
temperature, while the absorption of oxygen by phosphorus 
takes place quite slowly at temperatures below 14 C. Di- 
rect experiments showed that at a tejnperature of 7 C. 
the absorption of oxygen in the air was complete in five 
minutes. 

In the analysis of gas mixtures that contain carbon monox- 
ide the method cannot be used, because the basic ammonium 
cuprous carbonate, formed from the copper present, absorbs 
carbon monoxide. 



i68 GAS ANALYSIS 



5. Solutions of Ferrous Salts 

The oxygen in gas mixtures containing carbon monoxide can, 
according to Kostin, be removed by the use of a pipette filled 
with iron wire gauze that stands in a saturated solution of fer- 
rous sulphate to which has been added one-third of its volume 
of strong ammonia. It is preferable to employ a solution of 
ferrous chloride to which has been added ammonia and sufficient 
ammonium chloride to prevent the separation of ferrous hy- 
droxide. 

6. Sodium Hyposulphite 

Hyposulphurous acid was first prepared in 1868 by Schiitzen- 
berger. The formula of the compound was correctly determined 
by Bernthsen * in 1880. The sodium salt of the acid has re- 
cently become easily obtainable and for that reason Franzen 2 
has examined the substance with a view to ascertaining whether 
it could be used in gas analysis for the absorption of oxygen. He 
prepares the reagent by dissolving 50 grams of sodium hypo- 
sulphite in 250 cc. of water, and 30 grams of sodium hydroxide 
in 40 cc. of water, and mixing the two solutions. This final 
solution is placed in a Hempel pipette for solid reagents that has 
first been filled with small rolls of iron wire gauze. Franzen 
states that in this apparatus oxygen, if present in not too large 
amount, is completely absorbed in five minutes. The reaction 
that takes place is represented by the equation 

2Na 2 S 2 O 4 + 2 H 2 O + O 2 = 4 NaHS0 3 , 

from which it appears that one gram of sodium hyposulphite is 
able to absorb about 64 cc. of oxygen. One cc. of the above 
solution will consequently absorb 10.7 cc. of oxygen, and its 
analytical absorbing power (see p. 65) will therefore be about 
2.5. Franzen enumerates the following advantages possessed 

1 Berichte der deutschen chemischen Gesellschaft, 13 (1880), 2277. 

2 Berichte der deutschen chemischen Gesellschaft, 39 (1906), 2069. 



PROPERTIES OF THE VARIOUS GASES 169 

by sodium hyposulphite over other absorbents for oxygen. In 
the first place it is decidedly cheaper than pyrogallol; 1 secondly, 
it absorbs oxygen as rapidly at low temperatures as it does at 
higher, whereas the absorbing power of alkaline pyrogallol and 
of phosphorus shows marked decrease with fall of temperature. 
Furthermore the absorption of oxygen by the reagent is not 
influenced by gases that prevent the oxidation of phosphorus. 

If the reagent is to be used in the Bunte burette for the deter- 
mination of oxygen Franzen recommends the use of a solution 
somewhat less concentrated than that described above, and 
employs for this purpose a solution of ten grams of sodium 
hyposulphite in 50 cc. of water to which has been added 50 cc. 
of a ten per cent solution of sodium hydroxide. Shaking for 
three minutes suffices to completely remove the oxygen when 
that gas is present in not too great amount. 

7. Chromous Chloride 

Chromous chloride may be used for absorbing oxygen 2 in the 
presence of hydrogen sulphide and carbon dioxide. These two 
gases are completely indifferent to both the blue chromic chloride 
and the green chromous chloride solutions. 

Dennstedt and Hassler, however, state 3 that as an absorbent 
for oxygen it is open to objection because it easily gives off 
hydrogen. 

To prepare chromous chloride, Von der Pfordten has used the 
method given by Moissan. A green solution of chromic chloride 
free from chlorine is made by heating chromic acid with concen- 
trated hydrochloric acid, and this solution is then reduced with 
zinc and hydrochloric acid. Since spongy particles always 
separate from the zinc used for the reduction, the solution must 
be filtered. For this purpose the reduction is carried on in a 
flask fitted with a long and a short tube, as is a wash-bottle. 

1 The German price lists for 191 1 quote about $1.00 per kilogram. 

2 Otto von der Pfordten, Liebig's Annalen, 228 (1885), 112. 

3 Berichte der deutschen chemischen Gesettschaft, 41 (1908), 2780. 



i yo GAS ANALYSIS 

The longer tube is bent downward above the flask and is here 
supplied with a small bulb-tube, which is filled with glass-wool 
or asbestos. The hydrogen given off during the reduction is 
allowed to pass out through the longer tube for some time; then 
after closing its outer end the tube is pushed down into the solu- 
tion. The hydrogen is thus obliged to pass out through the 
shorter tube, which carries a rubber valve. Carbon dioxide is 
then passed into the flask through the short tube, and the 
chromous chloride solution is driven over into a beaker contain- 
ing a saturated solution of sodium acetate; a red precipitate of 
chromous acetate is formed which is washed by decantation 
with water containing carbonic acid. The red chromous acetate 
is, relatively speaking, quite stable, and in moist condition it 
may be kept for an unlimited time in closed bottles filled with 
carbon dioxide. 

In washing the red precipitate, some free acetic acid is added 
in the beginning, to dissolve any basic zinc carbonate which 
may have been thrown down. In this way a preparation com- 
pletely free from zinc is obtained. 

To absorb oxygen, the chromous acetate is decomposed by 
the addition of hydrochloric acid, the air being excluded. It is 
advisable to use an excess of chromous acetate in order to avoid 
the presence of free hydrochloric acid. 

OZONE 

Properties of Ozone. Specific Gravity = 1.62. 

Ozone, Os, is, at ordinary temperatures, a gas that possesses 
a peculiar, pungent odor. In a layer one meter thick it shows a 
distinctly blue color. It has a marked irritating effect on the 
mucous membrane. It is a powerful oxidizing agent. 

The Detection of Ozone. The detection of ozone, particu- 
larly in such small amounts as may be present in atmospheric 
air, has frequently been the subject of investigation, and many 
agents and many methods for accomplishing the object have 
been described in the chemical journals. 



PROPERTIES OF THE VARIOUS GASES 



171 



It has been found particularly difficult to identify, in the 
presence of one another, the three gases ozone, nitrogen tetroxide 
(peroxide) and hydrogen dioxide. This problem appears to have 
been satisfactorily solved by Keiser and McMaster, 1 who have 
also given an admirable summary of the earlier work that has 
been done in this field. For these reasons their article is here 
quoted in full: 

"When air is acted upon in a number of ways, such as by 
electric sparks, the flaming arc, burning hydrogen, burning 
magnesium, heated platinum wire, etc., in short, by any means 
which produce very high temperatures, ozone, nitrogen peroxide, 
and hydrogen peroxide may be formed. The silent electric dis- 
charge and the slow oxidation of phosphorus produce oxidizing 
gases in air. Several commercial processes of treating air so as 
to convert it into a more active chemical agent are at present in 
use. It is desirable, therefore, to have characteristic reactions 
for each of the three substances above mentioned in examining 
the gases produced in these different ways. 

" A great many reagents have been suggested for this purpose, 
but many of these have been found to be unreliable, while others 
are not very sensitive, and still others are rare substances that 
are not easily obtained. The following table contains a list of 
such substances, together with a statement of their behavior 
toward ozone, nitrogen peroxide, and hydrogen peroxide. 





Ozone 


Nitrogen 
peroxide 


Hydrogen 
peroxide 


Potassium iodide and starch 2 . 


blue 


blue 


blue 


Wine-red litmus paper mois- 








tened with potassium iodide 3 


blue 


no change 


blue 


Tetramethylparaphenylenedia- 








mine 4 


bluish violet 


bluish violet 


bluish violet 



1 Amer. Chem. J., 39 (1908), 96. 

2 Schoenbein: Ber. u. d. Verh. d. Nat. Ges., Basel, 4, 58. 

3 Houzeau: Compt. rend. 45, 873'. 

4 Wurster: Ber. d. deutsch. chem. Ges., 19, 3195. 



172 



GAS ANALYSIS 





Ozone 


Nitrogen 
peroxide 


Hydrogen 
peroxide 


Metaphenylenediamine, alkaline 


Burgundy 






solution l 


red or yellow 


no change 


no change 


Manganese chloride paper mois- 








tened with guiacum tincture 2 


blue 


blue 


no change 


Benzidine in alcohol 3 . . 


brown 


blue 


no change 


Tetramethyl-^-^-diaminodiphen- 








ylmethane in saturated 








alcoholic solution 4 ... 


violet 


yellow 


no change 


Potassium ferricyanide and ferric 








chloride 5 


no change 


no change 


blue 


Manganese dioxide or copper 








oxide 6 


decomposed 


no change 


decomposed 


Silver foil 7 


black 


no change 


no change 










Chromic acid and ether 8 


no change 


no change 


blue 


Chromic acid 9 


no change 




decomposed 


Titanium hydroxide in sulphuric 








acid 10 


no change 


no change 


yellow 


Thallous salts " 


brown 


no change 


no change 


Ammonium molybdate in sul- 








phuric acid 12 . . . . . 


no change 


no change 


yellow 


Guiacum tincture with malt in- 








fusion 13 


no change 


no change 


blue 


Gold chloride free from acid 14 . 


black 


no change 




Nitrite test with sulphanilic acid 








and o-naphthylamine 15 


no change 


pink 


no change 



1 Erlwein and Weyl: Ibid., 31, 3158. 

2 Engler and Wild: Ibid,, 29, 1940. 

3 Arnold and Mentzel: Ibid., 35, 1324. 

4 Ibid. 

6 Schoenbein, Weltzien, also Schoene: Ibid., 7, 1695. Engler and Wild: Ibid., 29, 
1940. 

6 Andrews and Tait: Ann. Chem. (Liebig), 112, 185. 

7 Ber. d. deutsch. chem. Ges., 35, 1326. 

8 Barreswill: Ann. chim. phys. (3), 20, 364. 

9 Engler and Wild: Ber. d. deutsch. chem. Ges., 29, 1940. 

10 Schoenn: Z. anal. Chem., 9, 41. 

11 Schoene: Ann. Chem. (Liebig), 196, 58. 

12 Schoenn: Z. anal. Chem., 9, 41. 

13 Struve: Ibid., 8, 315. 

14 Boettger: Ibid., 19, 105. 

15 Bull. Soc. Chim. (3), 2, 347 (1889). 



PROPERTIES OF THE VARIOUS GASES 173 

" Arnold and Mentzel 1 have studied a number of the reagents 
that are mentioned in the preceding list. They find that potas- 
sium iodide and starch, and zinc iodide and starch, as well as 
guiacum tincture, give a blue color with ozone, nitrogen per- 
oxide, chlorine, and bromine. In short, these reagents are not 
characteristic of anything more than an oxidizing gas. Red 
litmus paper moistened with potassium iodide solution they find 
to be entirely unreliable, because all paper turns blue with free 
iodine, and any gas that liberates iodine will turn the paper blue. 
They also found that a solution of potassium iodide to which 
wine-red litmus solution had been added was unsatisfactory, 
because the ozone acts upon the litmus and changes it to a green 
color. The third reagent in the above list, tetramethylpara- 
phenylenediamine, is also turned blue by all oxidizing gases. 
Metaphenylenediamine, the fourth one, was unsatisfactory be- 
cause they found that nitrogen peroxide gave the same color as 
ozone, and all oxidizing gases give yellowish colors with this sub- 
stance. Silver foil 2 is not satisfactory because it is not at all 
sensitive. Arnold and Mentzel recommend an alcoholic solution 
of benzidine or, still better, an alcoholic solution of tetramethyl- 
/>-/>-diaminodiphenylmethane. This gives a violet color with 
ozone and yellow with nitrogen peroxide; with hydrogen perox- 
ide it remains unchanged. They found, however, that the ozone 
obtained by the action of sulphuric acid upon barium dioxide 
had a different action upon this reagent; instead of violet a green 
color was obtained. Benzidine, under the same conditions, 
gave a blue instead of a brown color. Similar effects were ob- 
tained with the ozone from persulphates, percarbonates, and 
from sodium and hydrogen peroxides. 

"F. Fischer and Marx 3 have used tetramethyl-/>-/>-diarninodi- 

1 Ber. d. deutsch. chem. Ges., 35, (1902) 1324. 

2 Manchot and Kampschulte (Ber. d. deutsch. chem. Ges., 40, [1907] 2891) have 
recently shown that while silver foil is not at all sensitive at ordinary temperatures, 
it becomes much more so at 22o-24o C. For metallic mercury they found the 
temperature at which action was strongest to be 170 C. 

3 Ber. d. deutsch. chem. Ges., 39, (1906) 2555. 



174 GAS ANALYSIS 

phenylmethane or ' tetramethyl base,' as it is called, in their 
investigations upon the formation of ozone and nitrogen peroxide 
in air at high temperatures. They prepared ozone by the silent 
electric discharge in the Siemen's ozonometer, by the action of 
ultraviolet light, by the electrolysis of sulphuric acid, and in 
other ways, and found that ozone produces with this reagent a 
violet color and the oxides of nitrogen a yellow color. Mixtures 
of both gases give a dirty brown color intermediate between 
violet and yellow. Another fact that they emphasize is that the 
paper must always be kept moist; if it becomes dry, ozone 
changes it to a yellow color. To detect very small quantities of 
nitrogen oxides in the presence of ozone they recommend that 
the gas be conducted into liquid air. The ozone will dissolve 
while the oxides of nitrogen will separate as blue flakes. When 
the liquid air is then filtered, the frozen oxides of nitrogen re- 
main upon the filter. The filtrate is allowed to boil, the air 
distils away, and the ozone remains. In this way both can be 
separately identified. 

"This method is open to the objection that liquid air is not 
readily obtained in many places. Likewise the ' tetra base ' of 
Wurster and the 'tetramethyl base' of Arnold and Men tzel are 
not easily obtainable substances. Moreover, the color changes 
are not always satisfactory. Thallous salts and titanic acid are 
not always on hand. We have now, however, devised a method 
which is free from these objectionable features and enables us to 
identify each of these three substances in the presence of others. 

"We found that potassium permanganate, even in very di- 
lute solution, is not decolorized by ozone. Nitrogen peroxide 
and hydrogen peroxide, on the other hand, both reduce it in- 
stantly. To identify ozone in gases that contain at the same 
time nitrogen peroxide and hydrogen peroxide it is only necessary 
to draw the gases through a solution of potassium permanganate; 
the nitrogen peroxide and hydrogen peroxide will not pass 
through, while the ozone will, and can then be detected with 
potassium iodide and starch. 



PROPERTIES OF THE VARIOUS GASES 175 

"To detect nitrogen peroxide in the presence of ozone and 
hydrogen peroxide we take advantage of the fact that both 
ozone and hydrogen peroxide are decomposed when passed 
through a tube containing powdered manganese dioxide. Nitro- 
gen peroxide passes through unchanged. Its presence can be 
shown by passing the gas, after it has gone over the manganese 
dioxide, into very dilute permanganate. If the latter is decolor- 
ized, nitrogen peroxide was present. A still more delicate test 
for nitrogen peroxide is this: pass the gas, which may contain 
ozone and hydrogen dioxide, directly into pure caustic soda, 
made from metallic sodium and nitrite-free distilled water, and 
then test the caustic soda solution for nitrites by the well-known 
sulphanilic acid and a-naphthylamine method. 

"Hydrogen dioxide can be identified in the presence of both 
ozone and nitrogen peroxide by passing the gas mixture into a 
solution of potassium ferricyanide and ferric chloride. The 
yellow brown solution becomes green and then blue as more 
hydrogen dioxide passes in. This formation of Prussian blue is 
characteristic of hydrogen dioxide and is not produced by 
either ozone or nitrogen peroxide. This we have found by 
experiment. 

" Examination of the Gases Produced by Burning Hy- 
drogen in Air. We have triecl our method in the examination 
of the gases produced by burning hydrogen in air. A jet of 
burning hydrogen was introduced into the end of a glass tube 
fifteen millimeters in diameter. A current of air was drawn into 
the tube by means of an aspirator. The gas passed from the 
tube through a moderately strong solution of potassium perman- 
ganate and then into a solution of potassium iodide and starch. 
This soon became blue, thus showing that ozone was formed 
by the hydrogen burning in a rapid current of air. The potas- 
sium permanganate wash bottle was then replaced by a tube 
forty centimeters in length, filled with powdered manganese 
dioxide. Between this tube and the aspirator, a wash bottle 
with a very weak solution of potassium permanganate was in- 



1 76 GAS ANALYSIS 

serted. Air was now rapidly drawn through the apparatus and 
the products of combustion of the hydrogen passed first over 
the manganese dioxide and then into the dilute permanganate. 
The latter, after a time, became decolorized, thus showing that 
nitrogen peroxide was formed. This was confirmed by passing 
the gases formed by burning hydrogen into a solution of nitrite- 
free caustic soda and then applying the nitrite test (Griess test) 
after having slightly acidified the solution. The pink color was 
formed, thus confirming the result obtained with dilute per- 
manganate. The gases formed by burning hydrogen were also 
tested for hydrogen peroxide by drawing them through a solu- 
tion of potassium ferricyanide and ferric chloride. This became 
first green, then blue, thus showing that hydrogen peroxide was 
present. This ferricyanide and ferric chloride test for hydrogen 
peroxide we found to be more sensitive than titanium dioxide in 
sulphuric acid. The latter failed to show the presence of hydro- 
gen peroxide in the gases produced by burning hydrogen in air. 

" Examination of the Gases Produced by the Silent Elec- 
tric Discharge in Air and Oxygen. Atmospheric air was 
purified and dried by being drawn, by means of an aspirator, 
through a series of wash bottles containing silver sulphate, potas- 
sium permanganate, and pure concentrated sulphuric acid, and 
was then passed through a Siemen's ozonometer. The ozonometef 
was connected with the terminals of a Ruhmkorff coil which, in 
turn, was connected with a storage battery. The potential of the 
coil discharge terminals was 2160 volts. The air passing through 
the ozonometer in which the silent discharge was taking place 
was thereupon conducted through a very weak solution of potas- 
sium permanganate. No decolorization took place, although 
the ozonized air was passed for more than two hours. Ozone 
was shown to be present in quantity, not only by its action upon 
potassium iodide and starch after it had passed through the 
permanganate, but also by its odor and by the repeated perfora- 
tion of the rubber tube that connected the last wash bottle with 
the aspirator. We were surprised to find that, under these con- 



PROPERTIES OF THE VARIOUS GASES 177 

ditions, no nitrogen peroxide was formed. A quantitative de- 
termination of the ozone showed that there was 0.00086 gram 
per liter. We also conducted the air directly from the ozonom- 
eter into pure caustic soda and tested this for nitrites by the 
Griess test but failed to obtain any. With potassium ferri- 
cyanide and ferric chloride the ozonized air failed to give a re- 
action for hydrogen peroxide. The same results, namely, the 
absence of nitrogen peroxide and hydrogen peroxide in air that 
had passed through the Siemen's ozonometer, were obtained 
when we omitted washing the air with silver sulphate, caustic 
soda, potassium permanganate, and sulphuric acid before it 
entered the ozonometer. These experiments show conclusively 
that it is possible to ozonize air without, at the same time, form- 
ing nitrogen peroxide and hydrogen peroxide. We have repeated 
the above experiments with oxygen, made from fused sodium 
peroxide and water, instead of air. We obtained no nitrogen 
peroxide nor hydrogen peroxide. A quantitative determina- 
tion showed the presence of 0.0012 gram of ozone to the liter. 
This ozonized oxygen failed to decolorize potassium perman- 
ganate solution. 

" Examination of Gases Produced by the Action of Con- 
centrated Sulphuric Acid upon Barium Dioxide. Concen- 
trated sulphuric acid was allowed to drop upon barium dioxide, 
contained in an Erlenmeyer flask, and the gases resulting were 
conducted through a concentrated solution of potassium per- 
manganate in a Geissler potash bulb, and then into a solution 
of potassium iodide and starch. A blue color soon appeared, 
thus showing the presence of ozone. The gas, after passing 
over manganese dioxide and then into* permanganate, failed 
to give the reaction for nitrogen peroxide. Nor were we able 
to detect hydrogen peroxide by passing the gas through a solu- 
tion of potassium f erricyanide and ferric chloride. 

"A small quantity of barium nitrate was now added to the 
barium dioxide, and, on treating with concentrated sulphuric 
acid and testing as before, we obtained evidence of the presence 



iy8 GAS ANALYSIS 

of ozone and nitrogen peroxide, but not of hydrogen peroxide, 
in the gases given off. 

" Examination of the Gases Produced by the Slow Oxida- 
tion of Phosphorus in Moist Air. We have also used our 
method for the examination of the gases formed by the slow 
oxidation of phosphorus in air in the presence of water. We 
found ozone and nitrogen peroxide but no hydrogen per- 
oxide. 

" Examination of the Gases Produced by the Action of 
the Flaming Electric Arc upon Air. Air that had passed 
through the flaming electric arc of an Alsop process machine, 
such as is used in treating flour, was next examined by our 
method. We found that this air contained nitrogen peroxide, a 
trace of ozone, and a little hydrogen peroxide. 

"Examination of Atmospheric Air. We have applied our 
method to the examination of country air. Air from outside of 
the laboratory was drawn through a layer of absorbent cotton, 
six inches in length, then through a concentrated solution of 
potassium permanganate in a potash bulb, and finally into 
potassium iodide and starch. After the air had passed through 
for five hours, a faint blue color appeared, thus showing the 
presence of ozone. Air that was filtered through absorbent 
cotton and that had passed over a layer of manganese dioxide 
eighteen inches in length was conducted through a very faintly 
pink solution of permanganate. No decolorization was ob- 
served, although the air was drawn through for eighteen hours. 
We conclude from this that there was no nitrogen peroxide in 
the air. Air filtered through cotton was drawn through a solu- 
tion of potassium ferricyanide and ferric chloride. After four 
hours the solution acquired a green color. We found, however, 
that the reagent used for detecting hydrogen dioxide, namely, a 
dilute solution of ferric chloride and potassium ferricyanide, 
when allowed to stand in air, gradually forms a green precipitate, 
even when protected from dust by being covered with a bell jar. 
We, therefore, drew atmospheric air for five hours through pure 



PROPERTIES OF THE VARIOUS GASES 179 

distilled water, contained in a potash bulb, and then tested this 
water with the reagent. We obtained no blue precipitate, and, 
therefore, conclude that the green color mentioned above may 
not have been caused by hydrogen dioxide. These experiments 
prove that our method is sufficiently sensitive to show the pres- 
ence of ozone in atmospheric air." 

Determination of Ozone. An excellent method for the 
determination of ozone is that perfected by Treadwell and 
Anneler, 1 in which the ozonized oxygen is caused to act upon a 
neutral solution of potassium iodide, 

2 KI + 3 + H 2 O = 2 KOH + 2 I + O 2 . 

The liberated iodine is titrated with j^ sodium thiosulphate 
after first acidifying the solution with dilute sulphuric acid, 
i cc. Na2S2O 3 = 0.0024 gram OB. 

An acid solution of potassium iodide may not be employed 
because hydrogen dioxide is then formed and this sets free a 
further amount of iodine. 

4 O 3 + 10 HI + H 2 O = 10 1 + 3 O 2 + H 2 O 2 + 5 H 2 O. 

The gas sample is collected and measured in a bulb of the form 
shown in Fig. 78, which is a slight modification of that proposed 
by Treadwell. The bulb, B, has a capacity of from 300 cc. to 
400 cc. and its volume is accurately determined by weighing 
it empty and then filled with water, applying correction for tem- 
perature. 2 The carefully ground slip-joint of glass, A, serves to 
connect the bulb with the apparatus from which the ozonized air 
is to be drawn. Rubber or cork connections may not be used 
because both are attacked by ozone. 

The bulb is filled with distilled water, and the gas sample is 
drawn in through A by opening both stopcocks and allowing the 

1 Z.f. anorg. Chem., 48 (1905), 86. 

2 See Analytical Chemistry by Treadwell, translated by Hall (1911), vol. II, p. 678. 



i8o 



GAS ANALYSIS 



water to flow out. The lower stopcock H is then closed, and a 
few seconds later the upper stopcock C is closed. The inlet tube 
D is now removed and the stopcock C is opened for an instant 
to bring the gas to atmospheric pressure. The barometric 
pressure and the temperature of the room are read and 
recorded. 

The tube below H is connected by a piece of rubber tubing 
with the level-bulb S which is then filled with a twice-normal so- 
lution of potassium iodide. Air 
in the rubber tube is driven out 
through the end opening of the 
tail-stopper H, and the stopper 
is then turned and from 20 cc. 
to 30 cc. of the solution is forced 
into the bulb. H is now closed 
and the rubber tube is taken off. 
The bulb is vigorously shaken 
and allowed to stand for about 
half an hour, at the end of 
which time the absorption of 
ozone will be complete. The so- 
lution in the bulb is then run 
out into an Erlenmeyer flask, 
the bulb being rinsed with a 
small volume of the solution of 
potassium iodide and then finally 
with distilled water. The solu- 
tion is acidified with dilute sul- 
phuric acid and the free iodine 

is titrated with a ~ solution of sodium thiosulphate. In com- 
puting the per cent of ozone in the gas mixture, the vol- 
ume v of the gas sample in the bulb is first corrected to 
the volume VQ that it would occupy under standard con- 
ditions by means of the formula given on page 35. If n 




FIG. 



PROPERTIES OF THE VARIOUS GASES 181 

represents the number of cubic centimeters of j^ sodium thio- 
sulphate used in the titration of the free iodine, then 

112 x n 
per cent by volume of ozone = 

Vo 

Treadwell and Anneler do not discuss the possibility of inter- 
ference by nitrogen peroxide or hydrogen peroxide in their 
method for the determination of ozone nor do they describe any 
procedure for the removal of these gases. The ozone could 
probably be freed from the two gases by passing the mixture 
through a solution of potassium permanganate as recommended 
by Keiser and McMaster (page 174). 

HYDROGEN 

Properties of Hydrogen. Specific gravity, 0.06965 ; weight 
of one liter, 0.09004; boiling point, 252. 
According to L. W. Winkler, 1 one volume of water absorbs at 

o, 0.02148 vol. hydrogen 

5, 0.02044 
10, 0.01955 
15, 0.01883 
20, 0.01819 

At f alcohol takes up 

0.06925 0.0001487* + o.oooooi* 2 vol. of hydrogen; 
hence at 

20, 0.066676 vol. (Bunsen). 

Detection of Hydrogen. For the detection of hydrogen 
Phillips 2 recommends the use of dry palladious chloride which 
reacts with hydrogen with the formation of hydrogen chloride 
that then causes precipitation of silver chloride when the issuing 

1 Berichte der deutschen chemischen Gesellschaft, 24 (1891), 89. See also Timofejew, 
Zeitschr.fiir phys. Chem., 6 (1890), 141. 

2 American Chemical Journal, 16 (1894), 259. 



182 GAS ANALYSIS 

gases are passed through a solution of silver nitrate. Since, 
however, palladious chloride is reduced by the olefines and by 
carbon monoxide the method is applicable to the detection of 
hydrogen only in such gas mixtures as do not contain these con- 
stituents. Zenghelis 1 has recently described a method that may 
be used for the detection of hydrogen in the presence of such 
hydrocarbons as methane, ethylene and acetylene. It consists 
in passing the gas mixture through a solution of sodium hydrox- 
ide and then through a tube fitted with a tip of platinum foil or 
platinum wire gauze. The foil or gauze should be carefully 
ignited before the test is made. This delivery tube is immersed 
in a few cubic centimeters of a warm solution of sodium molyb- 
date contained in a test tube. The reagent is prepared by dis- 
solving one gram of molybdenum trioxide in dilute sodium 
hydroxide, adding dilute hydrochloric acid in slight excess and 
diluting to 200 cc. with water. When molecular hydrogen 
passes through the delivery tube it is occluded by the platinum 
and in this condition immediately reduces the ammonium molyb- 
date solution, imparting to the latter an intense blue color. If 
the amount of hydrogen is very small or if the molybdenum 
solution is cold, the color is a light greenish blue. Palladium is 
to be preferred to platinum in testing for hydrogen by this 
method, but the latter metal gives quite satisfactory results 
unless there is only a trace of hydrogen in the gas mixture. 
Arsine, phosphine and carbon monoxide will cause the reduction 
of the molybdenum solution and consequently these three gases 
must be removed before the test for hydrogen is made. 

Determination of Hydrogen by Absorption. A method for 
the volumetric determination of hydrogen by means of a liquid 
absorbent has recently been described by Paal and Hartmann. 2 
They employ for the absorption of hydrogen gas a solution of 
colloidal palladium with sodium protalbinate as protective 
colloid. To avoid the necessity of oxidizing the palladium 

1 Z.fiir analytische Chemie, 49 (1910), 729. 

~ Berichte der deutschen chemischen Gesellschaft, 43 (1910), 243. 



PROPERTIES OF THE VARIOUS GASES 183 

hydride after each absorption, they make use of the fact that 
hydrogen that has been absorbed by colloidal palladium is able 
rapidly to reduce organic nitro-compounds such as picric acid. 

C 6 H 2 (NO 2 )3 OH + 18 H = C 6 H 2 (NH 2 )3 OH + 6 H 2 O. 

Consequently when sodium picrate is added in excess to the 
solution of the absorbent, the solution will rapidly and quantita- 
tively absorb a large volume of hydrogen gas. 

The authors prepare the reagent by dissolving two grams of 
sodium protalbinate in 50 cc. of water, adding sodium hydroxide 
in slight excess and then slowly adding 1.6 grams of palladium 
chloride ( = i gram Pd) previously dissolved in 25 cc. of water. 
A reddish brown liquid results which remains clear. To this is 
added hydrazine hydrate drop by drop. Reduction takes place 
at once. The solution is allowed to stand for three hours and is 
then placed in a dialyzer and dialyzed against water until the 
outer water shows no further test for hydrazine hydrate or 
sodium chloride. The resulting solution is concentrated at a 
temperature of 68 to 70 and is then evaporated to dryness over 
concentrated sulphuric acid in a vacuum. Black, glistening 
plates result which are soluble in water without leaving a resi- 
due. 1 For the absorption of hydrogen, the authors dissolve 2.74 
grams of sodium picrate and 2.44 grams of 61.33% colloidal 
palladium (Kalle) in water and dilute the solution to 130 cc. 
The reagent may be used in a Hempel simple gas pipette. 
Analyses made with this absorbent show that hydrogen is com- 
pletely removed from a gas sample in from 10 to 30 minutes and 
that hydrogen may quantitatively be separated from nitrogen 
and saturated gaseous hydrocarbons. If ^oxygen is present with 
the hydrogen in the gas mixture the oxygen should first be re- 
moved by means of alkaline pyrogallol or other suitable ab- 
sorbent because of the fact that colloidal palladium will cause 
oxygen and hydrogen to unite. Carbon monoxide is not ab- 

1 Colloidal palladium in solid form prepared according to the above procedure 
may be obtained from Kalle and Company, Biebrich am Rhein, Germany. 



184 GAS ANALYSIS 

sorbed by the reagent, but the gas seems to retard the absorption 
of hydrogen by colloidal palladium. For this reason the authors 
recommend that carbon monoxide be first removed by ammonia- 
cal cuprous chloride and that the hydrogen in the residue be 
then absorbed by the palladium solution. 

Brunck has made a careful examination of the method of 
Paal and Hartmann with a view to ascertaining whether it is 
adapted to technical practice. 1 He finds that the procedure 
gives very satisfactory results and states that he regards it as 
even more accurate than the combustion method for the deter- 
mination of hydrogen. Brunck employs a Hempel gas burette 
with water as the confining liquid and a Hempel simple absorp- 
tion pipette for solid and liquid reagents, see page 55, for hold- 
ing the absorbent. The removal of the hydrogen is more rapid 
if the pipette is shaken or if it is filled with small glass balls of 
from 5 to 7 mm. diameter. The size of these glass balls should 
be such that when the pipette is filled with them it will still be 
able to hold from 80 to 90 cc. of gas. The absorbent is prepared 
either by dissolving two grams of colloidal palladium 2 in water 
and adding 5 grams of picric acid that has been neutralized with 
sodium hydroxide and diluting the whole to from 100 to no cc., 
or by dissolving the corresponding amount of the absorption 
mixture, which is now prepared ready for use by Kalle and Com- 
pany, in 100 cc. of water. This amount of the reagent has a 
theoretical absorbing power of 4369 cc. of hydrogen measured 
under standard conditions. Relatively small amounts of hydro- 
gen, 10 to 20 cc., are absorbed in about 5 minutes; somewhat 
larger amounts in about ten minutes. When, however, the gas 
mixture contains 50 per cent or more of hydrogen, the gas should 
be passed over into the pipette and allowed to stand for 5 
minutes, then drawn back into the burette so that the gas balls 
in the pipette again become moistened with the absorbent, and 

1 Chemiker-Zeitung, 34 (igio), 1313. 

2 Brunck states that the present market price of this substance in Germany is 10 
Marks a gram. 



PROPERTIES OF THE VARIOUS GASES 185 

then passed back again into the pipette. This should be con- 
tinued until no further diminution of gas volume is noted. The 
removal of hydrogen from 100 cc. of a gas mixture containing a 
high per cent of this gas takes from 20 to 30 minutes. This 
method is naturally best applicable to the determination of 
hydrogen in the presence of nitrogen or of methane, or of both 
of these gases. A series of analyses of a mixture of hydrogen 
and nitrogen shows that the determination of hydrogen is 
accurate to within o.i cc. which falls well within the limits of 
experimental error when the sample is not greater than 100 cc. 
and the analysis is made over water. 

The high cost of the reagent would constitute a serious objec- 
tion to its employment in technical practice were it not easily 
possible to regenerate it. This may be done 1 as follows: The 
reagent is transferred from the gas pipette to a flask and 
the pipette is rinsed with water which is added to the liquid in 
the flask. Very dilute sulphuric acid is added drop by drop to the 
solution so long as a precipitate results. A large excess of sul- 
phuric acid is to be avoided because it might cause the colloidal 
palladium to change to palladium sulphate through action of 
atmospheric oxygen. The precipitate which contains palladium, 
free protalbinic acid and unused picric acid is washed with 
water which, while it may dissolve some of the acids, carries no 
palladium into solution. The precipitate is then suspended in a 
small amount of water and is dissolved by adding sodium hydrox- 
ide drop by drop. Fresh sodium picrate is then added, and the 
solution diluted with water to its original volume of about 100 
cc. It is now again ready for use. 

In a recent article 2 Hempel states that the solution of col- 
loidal palladium foams very strongly anci that this necessitates 
waiting a considerable length of time after the absorption of hy- 
drogen is complete until the foam has disappeared and the gas 
residue can be transferred to the burette for measurement. He 

1 Paal, Chemiker-Zeitung, 34 (1910), 1332. 
2 Z./. angew. Chem., 25 (1912), 1841. 



i86 GAS ANALYSIS 

cites experiments carried on by Petschek which show that the 
absorbing liquid prepared according to the method of Paal and 
Hartmann slowly loses its absorbing power even when it stands 
in the dark. For this reason Hempel recommends that the re- 
agent be used over mercury in an absorption pipette and that 
small quantities of the freshly prepared absorbing liquid be 
employed for the analyses. 

Determination of Hydrogen by Explosion. Hydrogen may 
be determined by mixing the gas with not more than four times 
its volume 1 of pure oxygen, exploding the mixture and measur- 
ing the contraction of the gas volume. The gas mixture may 
be exploded over mercury in a eudiometer such as Bunsen em- 
ployed, or the explosion pipette described on page 141 may be 
used. The volume of hydrogen that was present is equal to 
of the observed contraction 

2 H 2 + O 2 =2 H 2 O. 

If air is employed instead of oxygen, it should be borne in mind 
that a mixture of hydrogen and air that contains less than 10 
per cent or more than 63 per cent of hydrogen is not explosive 2 
and that the most accurate results will be obtained when the 
ratio of the volume of the gas that does not enter into the ex- 
plosion to that of the hydrogen and oxygen uniting is about 4 
to i. The determination of hydrogen by explosion with oxygen 
or air is not well suited to technical gas analysis because the re- 
action is so violent as to necessitate the use of only a small vol- 
ume of hydrogen with consequent decrease in the accuracy of 
the results. Moreover, as Misteli points out 3 small amounts 
of hydrogen escape combustion in the determination of the 
gas by explosion. Furthermore when nitrogen is present there 
is possibility of error through the formation of oxides of 
nitrogen. 

1 Bunsen, Gasometrische Methoden, 2d ed., p. 119. 

2 Teclu, Journal fur praktische Chemie, 75 (1907), 212. 

3 J.fiir Gasbeleuchtung, 48 (1905), 802. 



PROPERTIES OF THE VARIOUS GASES 187 

Determination of Hydrogen with Combustion Pipette. 

Hydrogen may be determined with a high degree of accuracy 
by the combustion method described by the author and C. G. 
Hopkins. 1 In this method the hydrogen may first be introduced 
into the combustion pipette (see Fig. 74) and then burned with 
a mixture of equal parts of oxygen and air, or pure oxygen may 
be introduced into the pipette and the hydrogen be then passed 
in. Either procedure gives equally accurate results. In the 
first form of manipulation a sample (about 100 cc.) of the hydro- 
gen under examination is measured off in a burette and is then 
passed over into the combustion pipette. A mixture of about 
equal parts of oxygen and air containing an amount of oxygen 
more than sufficient for the combustion of the hydrogen is meas- 
ured off in the burette, and the burette and pipette are then 
connected by a bent glass capillary tube in the usual manner 
(see Fig. 75). The platinum spiral is heated to dull redness by 
means of an electric current, and the mixture of air and oxygen 
is slowly passed over from the burette into the pipette. During 
the combustion the current should be regulated by means of the 
rheostat so that the spiral is at no time heated beyond dull red- 
ness. The combustion of the hydrogen is complete almost as 
soon as sufficient oxygen has been introduced. When nearly 
all of the mixture of air and oxygen is passed into the pipette, 
the pinchcock at the top of the burette is closed and the spiral 
is kept at dull redness for sixty seconds. The current is then 
turned off, the pipette is allowed to cool and the residual gas 
is passed back into the burette and measured. In this form 
of the method the hydrogen is burned with a mixture of oxygen 
and air because if pure oxygen were used, the contraction in 
the gas volume in the pipette before an excess of oxygen is in- 
troduced would cause the mercury in the pipette to rise and 
submerge the platinum spiral. The results of a series of de- 
terminations of hydrogen made by this method are given in the 
following table: 

1 Jour. Am. Chem. Soc., 21 (1899), 398. 



i88 



GAS ANALYSIS 





I 

cc. 


II 

cc. 


III 
cc. 


IV 

cc. 


V 
cc. 


VI 

cc. 


VII 
cc. 


VIII 
cc. 


Hydrogen taken 


99.6 


IOO.O 


98.6 


99.8 


99.4 


95-35 


97-5 


5I-I5 


Oxygen and air 


















added 


99.6 


99-95 


99.9 


IOO.O 


99.1 


96.6 


99-75 


48.95 


Total . . 


199.2 


199-95 


198.5 


199.8 


198.5 


I9J-95 


197-25 


IOO. IO 


Residue after 


















combustion . 


50.0 


50.1 


50.8 


50.55 


49-7 


49.1 


51.2 


23-4 


Contraction 


149.2 


149.85 


147-7 


149-25 


148.8 


142.85 


146.05 


76.7 


Equivalent to 


















hydrogen 


99-47 


99-9 


98.47 


99-5 


99-3 


95-23 


97-37 


51-13 




Per ct. 


Per ct. 


Per ct. 


Per ct. 


Per ct. 


Per ct. 


Per ct. 


Per ct. 


Hydrogen 


















found 


99-9 


99 9 


99 9 


99 7 


99 9 


99 9 


99-9 


IOO.O 



In the other style of manipulation a measured amount (about 
100 cc.) of oxygen is passed into the combustion pipette, the 
sample of hydrogen under analysis (about 100 cc.) is measured off 
in the burette, the burette and pipette are connected, the spiral 
is brought to dull redness and the hydrogen is slowly passed into 
the pipette until the following confining liquid reaches the con- 
necting capillary. In either manner of manipulation, the confin- 
ing liquid, water or mercury, should not be driven further than 
this because if it were to come in contact with the hot part of 
the pipette directly over the platinum spiral the glass would 
probably crack. To insure the complete transferral of the hy- 
drogen from the burette into the pipette the level-tube of the 
burette is now lowered and about 25 cc. of gas is drawn back 
into it from the pipette. This is then driven over again into 
the pipette and the procedure is once more repeated. The 
spiral is kept at dull redness for sixty seconds longer, the pipette 
is then allowed to cool and the gas is passed back into the bu- 
rette and measured. 

The Absorption of Hydrogen by Palladium-black (Hem- 
pel). The classic method devised by Hempel for the separation 
of hydrogen from ethylene, nitrogen and gases of the paraffin 
series, in which the hydrogen without being mixed with oxygen 



PROPERTIES OF THE VARIOUS GASES 189 

is directly absorbed by palladium-black at a temperature of 
about 1 00, is one of the most accurate and satisfactory proce- 
dures for the determination of this gas that has ever been de- 
vised. The arrangement of the apparatus is shown in Fig. 79. 
The palladium-black is first rendered active by superficially 
oxidizing it by heating it to redness on the lid of a platinum 
crucible and slowly raising the crucible lid out of the flame. 
About four grams of this palladium-black is placed in the tube H 
which is made of soft glass tubing. This tube has an internal 
diameter of 4 mm. and is 10 cm. high. To the upper ends of H 
are connected the two bent capillary tubes D and E. E is con- 
nected with a gas pipette C that contains water, and that is used 
simply to render possible the passage of the gas back and forth 
through the palladium-black. The other capillary tube D is 
joined to the burette A that contains the gas mixture in which 
free hydrogen is to be determined. Gases other than hydrogen, 
nitrogen, ethylene, and methane and its homologues must pre- 
viously be removed by absorption. There is now brought up un- 
der the U-tube H a beaker containing water at a temperature of 
about 100. The point at which the water stands in the capillary 
of the pipette is noted, the pinchcock P is then opened and the 
gas mixture passed three times back and forth through the pal- 
ladium tube by raising and lowering the level-tube B. The 
beaker of hot water is now replaced by one containing water 
of the temperature of the room and the gas residue is twice 
passed back and forth through this tube to cool it. The gas is 
then drawn back into the burette until the water stands at the 
original point in the capillary of the pipette. P is then closed 
and the residual gas volume in the burette is measured. The 
difference between the measurements made before and after 
the absorption is equal to the hydrogen in the gas mixture plus 
the volume of the oxygen in the air that was originally inclosed 
in the U-tube when the apparatus was put together. 

This volume of oxygen in the U-tube may accurately be de- 
termined once and for all in the following manner. Somewhat 



190 



GAS ANALYSIS 




FIG. 79 



PROPERTIES OF THE VARIOUS GASES 191 

more than 100 cc. of air is drawn into a phosphorus pipette 
(Fig. 35) and allowed to stand until the oxygen has been re- 
moved and the fumes of phosphorus pentoxide have been ab- 
sorbed. The pipette is connected with a gas burette and the 
nitrogen in the pipette is passed over into the burette and is 
measured. The pipette is now connected with one end of the 
freshly rilled palladium tube which itself is immersed in a beaker 
of water of the temperature of the room. The other end of the 
U-tube is connected with the burette that contains the nitrogen. 
The level-tube of the burette is then raised and the nitrogen 
is driven over into the pipette until the confining liquid reaches 
the top of the burette. The pinchcock is then closed and the 
gas is allowed to stand in the phosphorus pipette for about three 
minutes. The gas is then drawn back into the burette and 
again passed over into the pipette. The residual nitrogen is then 
drawn back into the burette and its volume is read. The differ- 
ence between this and the first reading gives the volume of oxy- 
gen that was originally in the palladium tube. The palladium- 
black is regenerated from time to time by heating it on the lid 
of a platinum crucible in the manner above described. 

The Fractional Combustion of Hydrogen. In the analysis 
of those mixtures of gases that most commonly occur in technical 
practice, the determination of the majority of the constituents 
may be accomplished by the absorption of the gases by liquid 
reagents or by solid reagents immersed in liquids. This method 
is, however, not applicable to the determination of the gases of 
the paraffin series nor has it been possible until recently (see 
page 182) to remove hydrogen by means of a liquid absorbent. 
In gas mixtures or gas residues that contain hydrogen and only 
one member of the paraffin series, both gases may satisfactorily 
be determined by burning the gases simultaneously in the com- 
bustion pipette shown in Fig. 74, measuring the contraction, and 
ascertaining the volume of carbon dioxide that has been formed. 
The analysis of such a mixture of combustible gases by the ex- 
plosion method (see page 141) is not as accurate as that by the 



192 GAS ANALYSIS 

combustion method just referred to. Particularly is this true 
of the simultaneous determination of hydrogen and methane in 
gas residues that contain large amounts of these two gases, for 
in such case only a small portion of the combustible residue can 
safely be exploded and consequently any experimental error is 
multiplied five- to eight-fold when the results are calculated for 
the whole of the gas residue. Moreover, if two or more hydro- 
carbons of the same group are present with the hydrogen, the 
gases cannot be determined by any combustion or explosion 
method in which all of the combustible gases are simultaneously 
burned (see page 131). For these reasons a satisfactory method 
for the fractional combustion of mixtures of hydrogen and 
hydrocarbons of the paraffin group, a method by means of 
which the hydrogen gas alone may be burned without oxida- 
tion of the hydrocarbons, has long been sought and many differ- 
ent procedures have been suggested. 

Fractional Combustion of Hydrogen with Platinum or Pal- 
ladium Asbestos. The first method of fractional combustion 
was proposed by Henry 1 who found that he could remove hydro- 
gen and carbon monoxide from the mixture of these two gases 
with methane and nitrogen by passing the gases over platinum 
sponge heated to 177. Somewhat later Coquillion discovered 2 
that hydrogen and methane, when mixed with air, could be 
burned by passing the gases over a spiral of metallic palladium 
heated to bright redness by an electric current. In 1878 Bunte 
described 3 a method for the combustion of hydrogen in which 
the mixture of the gas with air or oxygen is passed over palladium 
that is heated externally to the desired temperature by means of 
a small flame. It was afterward found that if the temperature 
to which the metallic palladium is heated is kept below a certain 
point, methane does not burn and that consequently the deter- 
mination of hydrogen when admixed with methane may be 

1 Annals of Philosophy, 25 (1825), 428. 

2 Compt. rend., 83 (1876), 799; 84 (1877), 1503; 85 (1878), 1106. 

8 Berichte der deutschen-chemischen Gesellschaft, n (1878), 1123. 



PROPERTIES OF THE VARIOUS GASES 193 

effected in this manner. Other contact substances for the frac- 
tional combustion of hydrogen have been suggested. 1 In later 
articles upon this subject, different authors called attention to 
the fact that some or all of the methane will burn with the 
hydrogen if the temperature is allowed to rise too high, but con- 
siderable difference of opinion existed as to the temperature to 
which the catalytic substance might be heated without causing 
oxidation of the methane. In fact, in many of the published 
methods, the authors contented themselves with a descrip- 
tion of some arbitrary method of heating the tube containing 
the catalyzer and evidently assumed that when the condi- 
tions that they laid down are followed, no methane will be 
burned. For example, in the instructions given by different 
writers concerning the heating of the glass tube containing 
palladium wire or palladium asbestos are to be found such state- 
ments as the following: "the heating of a tube should be gentle 
and in no case should it cause a visible glow:" "the tube should 
be heated to such a temperature that it can be touched for a 
moment without burning the finger:" "the tube should be 
heated to such a temperature as will just be sufficient to cause 
the potassium or sodium in the glass to color the Bunsen flame." 
It is true that the last statement was made by a writer who 
ascertained by means of a thermocouple that the difficultly 
fusible glass tubing that he was using began to color the Bunsen 
flame at a temperature lying between 550 and 600, but his 
directions would be of dubious value to another operator using 
a different sample of hard glass. Moreover, as Richardt has 
pointed out, 2 finely divided contact substances such as palla- 
dium asbestos, platinum asbestos or palladium sponge are poor 

1 Palladium asbestos, Winkler, Anleit. z. chem. Unters. der Industrie-Case, part 2, 
p. 258. 

Palladium sponge, Hempel, Berichte der deutschen chemischen Gesettschaft, 12 
(1879), 1006. 

Platinum asbestos, Kopfer, Berichte der deutschen chemischen Gesettschaft, 9 (1876), 

1377- 

2 Z./. anorg. Chem., 38 (1904), 65. 



194 GAS ANALYSIS 

heat-conductors, and for this reason the heat developed by the 
combustion of tjie gases within the tube may locally raise the 
catalyzer to a temperature at which methane will burn, even 
when the external heating of the tube is very carefully regulated. 
The observation of Winkler 1 that even when the glass capillary 
tube containing palladium asbestos is very carefully heated by 
a small gas flame "the end of the asbestos thread against which 
the entering current of gas impinges is heated to a bright glow, 
and that this glow is frequently again seen when the gas sample 
is passed back into the burette" is one that is familiar to all who 
have used this method of fractional combustion. 

To ascertain the temperature at which methane, when mixed 
with air, will be oxidized upon passage over a catalytic agent 
Richardt 2 passed the gas mixture over palladium wire that was 
placed in a capillary tube which was heated from the outside by 
a small flame. He employed palladium wire instead of palladium 
asbestos because the compact metal, having high heat conduc- 
tivity, rendered it possible to avoid local superheating. He 
found that methane was oxidized to some extent at a tempera- 
ture but slightly above 450 and that it rapidly burned at 
temperatures above 700. From these measurements it is 
evident that if the catalytic substance is heated to a dull red 
glow that is visible in daylight, which according to Richardt 
corresponds to a temperature from 750 to 800, combustion of 
some of the methane will undoubtedly result. 

Results confirmatory of the statements of Richardt were later 
obtained by Denham 3 who found that the temperature of com- 
bustion of practically pure methane and oxygen when the gas 
mixture is passed through a tube containing palladium asbestos 
lies between 514 and 546. 

Brunck maintains 4 that the results obtained in the fractional 

1 Lehrbuch der technischen Gasandyse, 1901, 168. 

2 Loc. cit. 

3 /. Soc. Chem. Ind., 24 (1905), 1202. 
*Z,f. angew. Chem., 16 (1903), 695. 



PROPERTIES OF THE VARIOUS GASES 195 

combustion of hydrogen by means of palladium asbestos are 
accurate even when the asbestos thread visibly glows during the 
passage of the gas mixture, but even his own confirmatory 
analyses show that with slight elevation of the temperature of 
the capillary tube, some methane is oxidized. If the palladium 
asbestos glows during the passage of the gas its temperature is 
undoubtedly considerably above 500. With this fact in mind 
it is difficult to reconcile the statements of Brunck with the 
experimental results of Nesmjelow 1 which appear to demon- 
strate that when a mixture of hydrogen, methane and air is 
passed through a capillary tube that contains palladium asbestos 
an appreciable amount of methane is oxidized at 150. It is 
certainly the case that when the fractional combustion of hydro- 
gen by means of palladium asbestos is carried out in the manner 
prescribed in almost all of the various descriptions of the method, 
the temperature of 150 will be greatly exceeded, particularly 
when a porous catalyzer is employed. 

In a recent review 2 of this method Hempel finds that hydrogen 
may be determined with accuracy in the presence of methane 
and ethane if the palladium asbestos does not glow during the 
analysis, and if the temperature of the capillary itself does not 
rise appreciably above 400. He states that this may be accom- 
plished by heating the capillary in a certain manner, which he 
describes, and by passing the gas mixture very slowly through 

1 Z.f. analytische Chemie, 48 (1909), 232. 

In this article Nesmjelow gives the following directions for the preparation of 
palladium asbestos: 

Dissolve three grams of sodium palladious chloride in as small an amount of water 
as possible, add three cc. of a cold, saturated solution of sodium formate, and then 
sodium carbonate to strong alkaline reaction. Place in the solution one gram of 
long-fibered, soft asbestos which will absorb practically all of the liquid. Dry the 
fiber on the water-bath. Metallic palladium will hereupon separate evenly on the 
asbestos in a black, finely divided form: 

Na 2 PdCl 4 + HCOONa =3 NaCl + HC1 + C02 + Pd. 

After complete drying on the water-bath, the asbestos is softened with water, and 
then is placed in a funnel and washed with warm water until the adhering salts are 
removed. It is then dried and kept in stoppered glass bottles. 

2 Z.f. angew. Chetn., 25 (1912), 1841. 



196 GAS ANALYSIS 

the tube, and that if these directions are followed with the greatest 
care the method gives agreeing results. These statements by 
Hempel serve to accentuate the uncertainty inherent in the 
fractional combustion of hydrogen by means of a catalytic sub- 
stance that is heated with a free flame, and they render it evident 
that slight variations in the procedure may easily give rise to 
errors of considerable magnitude. 

A much more satisfactory procedure for the fractional com- 
bustion of hydrogen is Hempel's method of burning the hydrogen 
by means of palladium black that is kept at a temperature below 
100, or that of Jager in which the fractional combustion of the 
hydrogen is accomplished by passing the gas over copper oxide 
at a temperature of 250. 

Fractional Combustion of Hydrogen with Palladium Black 
(Hempel) . The method is based upon the fact that if a mix- 
ture of hydrogen, methane and air, oxygen being present in ex- 
cess, is passed over palladium black at a temperature not above 
100, hydrogen alone is burned. 

Finely divided palladium is prepared for use in this method by 
heating it to redness upon the lid of a platinum crucible and 
gradually removing it from the flame so that it will cool slowly. 
This covers the metal with a very thin layer of palladious oxide. 

About 0.5 gram of this palla- 
dium black is placed in a small 
U-shaped glass tube (Fig. 80). 
This tube is connected by short 
pieces of rubber tubing with the 
^^3^ bent capillary tubes EE one of 

pj G 8o which is joined to a gas bu- 

rette while the other is con- 
nected with a simple gas pipette filled with water. 

From 15 to 20 cc. of the mixture of hydrogen and methane is 
brought into a Hempel burette and accurately measured. There 
is then drawn into the burette such an amount of air as will 
insure the presence of more than enough oxygen to unite with 




PROPERTIES OF THE VARIOUS GASES 



197 



the hydrogen in the gas mixture. The total volume of the gas is 
now measured. The right hand capillary E having been con- 
nected with a gas pipette filled with water, the left hand capil- 
lary is now joined to the burette containing the gas sample and 
air, and a beaker containing water of a temperature of from 60 
to 80 is brought up under the U-shaped tube and set at such a 
height that the water stands just below the lower ends of the 
rubber connections. The gas mixture in the burette is now 
passed very slowly through the palladium tube into the pipette. 
With too rapid a passage of the gas mixture over the palladium 
black the heat developed by the combustion of hydrogen may 
raise the palladium to a temperature at which methane will begin 
to burn. With reasonable care, however, the temperature of the 
U-tube and of its contents may easily be kept below 100 and the 
combustion of methane entirely avoided. The gas mixture is 
passed backward and forward from burette to pipette until no 
further decrease in the volume of the gas is observed. The 
beaker of warm water is then removed and is replaced by a 
beaker filled with water of the temperature of the room. When 
the residual gas has in this manner been brought to room tem- 
perature, the diminution of the volume of the gas is read. The 
volume of hydrogen in the sample is equal to two-thirds of the 
contraction noted. Hempel gives the following results as con- 
firmatory of the accuracy of this method. 



COMPOSITION OF THE GAS MIXTURE 




HYDROGEN 


Hydrogen 


Marsh-gas 


Air 


RESULTING 
CONTRACTION 


CALCULATED 

FROM THE 

CONTRACTION 


I- 5 


12.0 


85-1 


2.3 


i-5 


3-0 


8-3 


86. 5 


4-5 


3-0 


5-i 


12.3 


86.0 


7-6 


5-o 


9-3 


7-i 


83-7 


14.1 


9-4 


13-7 


7-3 


77-5 


20.3 


13-5 


14.1 


5-4 


81.2 


21 . 2 


14.1 


14.6 


4-5 


80.6 


22. I 


14.7 


13-1 


6.0 


80.3 


19.7 


i3-i 



198 GAS ANALYSIS 

An objection that may, however, be urged against this method 
is that only a portion of the combustible residue is employed and 
consequently an experimental error in the combustion is multi- 
plied several times when the result is calculated for the total 
residue. 

Fractional Combustion of Hydrogen with Copper Oxide 
( Jager) . The use of copper oxide for the determination of 
gaseous hydrocarbons was proposed by Fresenius as long ago as 
I864, 1 and the method was afterward further developed by 
Scheurer-Kestner 2 and Stockmann. 3 

Jager was the first who proposed the use of copper oxide in the 
fractional combustion 4 of hydrogen in the presence of methane, 
hydrogen being completely burned when passed over copper 
oxide 5 at a temperature of 250, whereas methane is not oxidized 
at all under these conditions. Jager places copper oxide in a 
hard glass tube 6 cm. in length and one cm. in external diameter. 
One end of the tube terminates in a straight capillary tube 3 cm. 
long. To the other end is fused a glass tube 4 cm. in length and 
5 mm. internal diameter through which the fine granular copper 
oxide is introduced. This combustion tube is connected on one 
side to a gas burette and on the other to a Hempel simple gas 
pipette containing a solution of potassium hydroxide. To facili- 
tate the control of the temperature the combustion tube rests in 
a small oven of sheet iron through the top of which a thermom- 
eter is inserted to such a distance that its bulb rests directly 

1 Z.f. analytische Chemie, 3 (1864), 339. 

2 A. Scheurer-Kestner, Bullet, de la Societe industriette de Mulhouse, 1868; Civil- 
ingenieur, N. F., XV, 123. 

3 C. Stockmann, Die Case des Eochofens und der Siemens-Generator en, Ruhrort 
1876, 6. 

4 Jour. f. Gasbeleuchtung, 41 (1898), 764. 

5 The oxygen for the combustion of hydrogen comes from the solid copper oxide 
which on reduction decreases in volume. Consequently the results obtained by 
measuring the contraction of the gas volume are somewhat too high. The error from 
this source is, however, so very small that it may be entirely disregarded. For ex- 
ample, in the determination of hydrogen, the correction would be 0.00047 cc. for 
each cubic centimeter of the gas. 



PROPERTIES OF THE VARIOUS GASES 199 

against the combustion tube. The oven is heated from below by 
a single gas burner. In the fractional combustion of hydrogen 
in a mixture of that gas with methane and nitrogen the combus- 
tion tube is first heated to 250, and the gas mixture is then 
slowly passed through it from the burette into the pipette. 
Jager found that a double passage of the gas through the tube 
usually suffices for the complete combustion of the hydrogen, 
but the gas mixture is usually passed through the tube a third 
time to ascertain whether further diminution in volume takes 
place. Since the oxygen of the air that is originally contained 
in the combustion tube burns with the hydrogen, the contrac- 
tion due to this source must be ascertained. Jager does this once 
and for all by passing through the heated combustion tube a 
mixture of known volumes of hydrogen and nitrogen. The 
observed contraction less the contraction due to the hydrogen 
used gives the volume of the oxygen in the combustion tube. 

The method is distinctly superior to the fractional combustion 
of hydrogen by palladium or palladium asbestos because 

1. No air or oxygen is added to the combustible gas, which 
makes it possible to pass the total gas residue through the 
tube with consequent gain in accuracy of the analytical re- 
sults : 

2. The temperature at which the hydrogen burns, 250 C., is 
so easily controlled and is so far below the temperature at which 
methane will be oxidized as to render impossible the combustion 
of any of the methane; 

3. The material and apparatus are inexpensive. 

To avoid the necessity of determining the volume of oxy- 
gen in the combustion tube and of making correction for it, 
v. Knorre * first fills the tube with nitroge'n, this gas being passed 
into the combustion tube through a T-tube that is introduced 
between the combustion tube and the pipette. He obtains the 
necessary volume of nitrogen by passing air into a phosphorus 
pipette (page 164) and he states that the nitrogen residue from 

1 Chemiker-Zeitung, 33 (1909), 717. 



200 GAS ANALYSIS 

100 cc. of air is amply sufficient to displace the oxygen in the 
combustion tube. 

Jager recommended that the methane in the gas residue be 
determined, after the fractional combustion of hydrogen, by 
' raising the temperature of the combustion tube to bright red- 
ness, passing the mixture of methane and nitrogen through the 
tube and ascertaining the volume of methane by determining 
either the contraction or the volume of carbon dioxide formed 
in the combustion. Methane, however, is not easily burned by 
passage over hot copper oxide and complete combustion of the 
gas is effected only by repeatedly passing it through the com- 
bustion tube. Moreover, since the tube itself must be kept at a 
bright red heat throughout the process, it frequently softens 
and if a drop of water enters it, it instantly breaks. These 
difficulties in the determination of methane are avoided by 
v. Knorre by substituting for the hard glass tube a tube of 
transparent quartz 15 cm. long, 5 mm. internal diameter and 
with a thickness of wall of from 0.5 to 0.75 mm. 

Ubbelohde and de Castro 1 also use a quartz tube rilled with 
copper oxide which they heat to 270 for the combustion of the 
hydrogen, and then to bright redness (800 to 900) to burn 
the methane and ethane. In the latter combustion they heat the 
quartz tube with a free flame and place a clay trough over the 
tube to bring the temperature to the highest point possible. 

Excellent as is the Jager method for the accurate determina- 
tion of hydrogen, the subsequent combustion of methane at a 
higher temperature in the same tube cannot unqualifiedly be 
recommended. If hard glass is used for the combustion tube, 
the tube must either be ordered from a glass blower or the chem- 
ist who makes his own simple glass apparatus must purchase 
both small tubing and capillary tubing of hard glass for fusion 
to the ends of the combustion tube proper. The glass tube is 
also apt to break when heated or when water is carelessly al- 
lowed to enter it during the combustion. The quartz tube is 

1 /./. Gasbeleuchtung, 54 (1911), 810. 



PROPERTIES OF THE VARIOUS GASES 201 

more durable, but apparatus of transparent quartz is fragile and 
expensive and, in this country at least, it cannot as yet readily 
be obtained. The chief objection, however, to this method 
of determining methane lies in the fact that prolonged heating 
of the combustion tube to a high temperature and repeated 
passage of the gas through it are necessary for the complete 
oxidation of the methane. Because of these considerations the 
author deems it preferable to restrict the combustion with cop- 
per oxide to the fractional combustion of hydrogen, and to de- 
termine the residual methane by combustion with oxygen in 
the Dennis combustion pipette. JSince the combustion tube need 
be heated only to 250 if hydrogen alone is to be burned, this 
modification of the procedure makes it possible to use a tube 
of soft glass which can easily be blown by the operator himself. 
The subsequent determination of methane by means of the 
combustion pipette is fully as accurate as the combustion with 
copper oxide and is much more rapid. The following arrange- 
ment and manipulation of apparatus have been found to give 
very satisfactory results. 

The combustion tube (Fig. 81) is made of soft glass throughout. 
It consists of a piece of glass tubing H, 7 cm. long, 12 mm. ex- 
ternal diameter, and one mm. thickness of wall; to one end of 
this tube is fused a piece of glass tubing 6 cm. long and 7 mm. 
external diameter; to the other end is fused a piece of capillary 
tubing of the dimensions used in the Hempel pipettes, namely, 
6 mm. external diameter and one mm. internal diameter, which 
is then bent at a right angle as shown in the figure. H is filled 
through the wide end with granular copper oxide which is held 
in place by a loose plug of ignited asbestos. Inasmuch as the 
temperature of the copper oxide during the combustion should 
be kept nearly constant at 270, the combustion tube is not 
heated with a free flame, but is placed in a small air-bath, /. 
Ubbelohde and de Castro employ an oven made of sheet iron 
and lined with asbestos, and fitted with two perforated iron 
plates for the even distribution of the heat. A device that is 



2O2 



GAS ANALYSIS 



simpler and fully as satisfactory may be constructed in the 
laboratory from ordinary asbestos board. A piece of asbestos 
board 9 cm. wide, 30 cm. long and 6 mm. thick is creased at 




FIG. 8 1 

points about 7.5 cm. apart, bent into a four-sided form and the 
ends connected by shaving one down to a sharp edge, splitting 
the other, inserting the narrow edge in the split end and then 
thoroughly wetting the asbestos and pressing it together. The 
two opposite sides of this box are notched to a depth of about 



PROPERTIES OF THE VARIOUS GASES 203 

4.5 cm. and the small combustion tube rests in these notches. 
The box, which is open at the bottom, rests upon a piece of 
sheet iron that is supported on an iron ring, M . An asbestos 
top, with sides 6 cm. high, is made from asbestos board in the 
same manner and opposite sides of the top are notched so that 
the top will set down over the box and completely close it ex- 
cept where the combustion tube passes through. A small open- 
ing in the top made with a cork borer serves for the introduc- 
tion of the thermometer T which is placed in such position that 
its bulb rests against the side of the combustion tube. The 
air bath is heated by a single Bunsen burner, C. A flame about 
6 cm. high suffices to keep the interior of the box and the com- 
bustion tube at a temperature of 270. 

Although the little asbestos oven is not heated higher than 
the comparatively low temperature of 270 throughout the 
determination it is advisable for the protection of the burette 
and the pipette to place strips of asbestos board, AA, about 
15 cm. wide, between the pipette and the oven on the one side 
and the oven and the burette on the other. 

In making a determination of hydrogen with this apparatus 
the combustion tube is placed in position in the asbestos box, 
and its left-hand end, Fig. 81, is connected with a water- jacketed 
Hempel burette that contains water 1 as the confining liquid 
and that has previously been filled with nitrogen from a phos- 
phorus pipette. 

1 Mercury may of course be used as the confining liquid, and a burette with correc- 
tion tube and manometer may be employed if great accuracy is desired. In tech- 
nical practice, however, results that are correct to within one-tenth of one per cent 
are usually sufficiently accurate, and inasmuch as the manipulation of the appara- 
tus is more simple and more rapid when water is used as the confining liquid in- 
stead of mercury, the method here described for the* determination, over water, of 
not only hydrogen but of methane as well, has been worked out for the convenience of 
the general analyst. If methane is the only hydrocarbon that is present with the 
hydrogen, the two gases may more rapidly be determined by the simultaneous com- 
bustion of both with the combustion pipette, but in such case mercury must be used 
as the confining liquid in both burette and pipette. Furthermore, if two members 
of the paraffin group (e. g., methane and ethane) are present in the gas residue after 
the hydrogen has been removed by fractional combustion with copper oxide, the 



204 GAS ANALYSIS 

The pinchcock E at the top of the burette is opened and the 
nitrogen is passed through the combustion tube into the outer 
air. This washes out the air in the combustion tube, and frees 
it practically completely from all oxygen. The pinchcock E 
of the burette is closed and a simple gas pipette filled with water 
up to the top of the rubber connecting tube at G is at once joined 
to the combustion tube. 

The rubber tube on the other end of the combustion tube is 
now closed by the pinchcock F, the burette is disconnected from 
the bent capillary tube and about 100 cc. of the gas mixture 
under examination, which should of course previously have 
been freed from all gases except hydrogen, nitrogen and members 
of the paraffin series, is drawn into the burette and measured. 
While this is being done the heating of the asbestos oven sur- 
rounding the combustion tube is begun and the pinchcock F is 
opened for a moment from time to time to relieve the excess 
pressure due to the expansion of the nitrogen in the tube. The 
heating is continued until the thermometer shows a temperature 
of 270 and the tube is kept at about this temperature during the 
combustion. The pinchcock F is then once more opened to bring 
the nitrogen in the combustion tube to atmospheric pressure and 
the burette is then connected with the bent capillary tube. 
The pinchcocks E, F and G are now opened and the gas mixture 
in the burette is slowly passed through the 'combustion tube into 
the water pipette. If the gas is passed through the tube at the 
rate of about 10 cc. per minute it has been found that four or 
five passages of the gas will completely remove the hydrogen 
from 100 cc. of a gas mixture that contains 40% of this gas. 

two paraffins can be determined in the combustion pipette only when mercury is 
used as the confining liquid. In gas analysis, as in any other line of analytical work, 
it should constantly be borne in mind that the refinements of a method should be in 
accord with the accuracy that is desired. In the present instance, if results that are 
correct to within about one-tenth of one per cent meet the needs of the case, it would 
involve useless consumption of time to employ a very accurate gas burette and 
to measure the gases over mercury. On the other hand, if great accuracy is desired, 
it would be folly to attempt to attain it by measurement of gas volumes over 
water. 



PROPERTIES OF THE VARIOUS GASES 205 

With a higher percentage of hydrogen, or in fact in any case, the 
gas should be passed backward and forward through the com- 
bustion tube until two successive readings are the same. After 
the removal of the hydrogen is completed, the gas is drawn back 
into the burette until the water in the capillary of the pipette 
stands just above K. The pinchcock G is then closed. The 
temperature of the combustion tube is now brought again to 
exactly 270 by raising or lowering the Bunsen flame, and the 
pinchcock E is closed. The gas is allowed to stand in the burette 
for two minutes to come to the temperature of the surrounding 
water and its volume is then read. The contraction in volume 
shows directly the amount of hydrogen. 

If it is desired to determine methane in the gas residue in the 
burette, the water pipette is replaced by a combustion pipette 
(Fig. 74) that is filled with water l and that contains a measured 
amount of oxygen, about 100 cc. The terminals of the pipette 
are connected with a source of electric current, the current is 
turned on, and the spiral is heated to dull redness. The com- 
bustion tube H is kept at about 270. The level-bulb of the 
pipette is placed upon the top of the stand S. A Hofmann de- 
tachable screw pinchcock is placed upon the rubber tube that 
connects the burette with its level-tube; the level- tube of the 
burette is then brought to such height that the confining liquid 
in it stands but slightly higher than the confining liquid in the 
burette, and the screw pinchcock is now closed. The level-tube 
is placed upon the top of another wooden stand like S. The 
pinchcocks E, F, and G are opened and set back on the glass 
tubes. The screw pinchcock is then very carefully opened, 
and the gas in the burette is very slowly started over through H 
into the combustion pipette. When the water in the burette 
has risen to the top of the burette, the pinchcocks E, F, and G 
are closed, and the burette is disconnected from the small capil- 
lary tube at E. The burette is then connected to a phosphorus 
pipette containing nitrogen and a known volume, from 15 to 

1 Mercury may of course be used. 



206 GAS ANALYSIS 

20 cc., of nitrogen is drawn into the burette. The burette is 
then disconnected from the phosphorus pipette and is again 
connected to the small capillary at E. Pinchcocks E, F, and G 
are opened, and the gas forced from the burette through the tube 
H into the combustion pipette as before. When the water in 
the burette reaches the top of the. burette, pinchcock E is closed, 
and the tube H is again brought to exactly 270 C. The gas in 
the combustion pipette is now brought to atmospheric pressure 
by proper adjustment of the height of the level-bulb of the 
pipette and the pinchcock G is then closed. The burette and 
the combustion pipette are disconnected from the tube H, 
and the burette is joined directly to the combustion pipette 
by a capillary tube of the usual form. The gas is drawn from 
the combustion pipette into the burette and is then passed 
into a pipette containing a solution of potassium hydroxide 
to remove carbon dioxide. The residual gas is now brought 
back into the burette, and is again measured. To ascertain 
the volume of methane in the sample, add the volume of gas 
remaining after the determination of hydrogen to the sum of 
the oxygen introduced into the combustion pipette and the 
volume of nitrogen used for sweeping the residual gas out of 
the tube H. From this sum, deduct the final volume of the gas 
that remains in the burette after the absorption of the carbon 
dioxide formed in the combustion of the methane. One-third 
of this result is the volume of the methane in the gas sample. 

NITROGEN 

Properties of Nitrogen. Specific gravity, 0.9701. Weight 
of one liter, 1.2542 grams. 

Nitrogen is but slightly soluble in water, one volume of 
water absorbing, according to Bunsen, at 760 mm. pressure 
and f, 

0.020346 - 0.00053887 t + 0.000011156 t 2 vol. of nitrogen: 
or at 



PROPERTIES OF THE VARIOUS GASES 207 

5, 0.01794 vol. 
10, 0.01607 " 
15, 0.01478 " 
20, 0.01403 " 

Otto Pettersson and K. Sonden 1 state that at a pressure of 
760 mm. i liter of water absorbs from the air: 

at o, 19.53 cc. 

6, 16.34 ' 
" 9.18, 15.58 " 
" 14.10, 14.16 " 

According to Carius, one volume of alcohol takes up at f, 

0.126338 0.000418 t + 0.000006 t 2 vol. of nitrogen; 

hence at 

20, 0.122378 vol. 

Absorption of Nitrogen. In the analysis of gas mixtures 
the residue that cannot be determined by the usual absorption 
methods or by combustion was earlier regarded as consisting 
wholly of nitrogen and is still commonly reported as such. From 
the researches of Rayleigh and Ramsay we now know that this 
residue frequently contains, in addition to nitrogen, one or more 
of the gases of the argon group, which consists of argon, neon, 
krypton, xenon and helium. In the earlier work in this field, 
nitrogen was separated from the gases by passing the gas mixture 
over hot magnesium, lithium, or a mixture of magnesium and 
calcium oxide, any of which agents unite with the nitrogen but 
do not affect the gases of the argon group. 

To obtain information as to the relative efficiencies of these 
various absorption agents, Hempel placed the different sub- 
stances in hard-glass tubes, exhausted these tubes of air, and 
then introduced an excess of nitrogen. The tubes were then 
heated to bright redness, the nitrogen was pumped out and 

1 Berichte der deutschen chemischen Gesellschaft, 22, (1889), 1443. 



208 



GAS ANALYSIS 



measured, and the amount of that gas which had been held back 
by each absorbent was thus determined. 
The results were as follows: 



ABSORPTION AGENT EMPLOYED 


Ti!lls8 

i*iili| 
*5pr s 


Number of 
Cubic Centi- 
meters of Ni- 
trogen that 
was absorbed 
in one hour 


i gram magnesium powder, medium fine . 
i gram lithium . ' . . . ' 





M-5 
77 . c 


i gram magnesium and 5 grams quicklime. The 
lime was not freshly ignited 
i gram magnesium and 3 grams quicklime. The 
lime was not freshly ignited 
i gram magnesium and 8 grams quicklime. The 
lime was not freshly ignited 
i gram magnesium and 5 grams quicklime. The 
lime was highly ignited shortly before the 
experiment . . . . . . 


94-5 
86.4 


112. O 
5O.O 
31-4 

122-5 


i gram magnesium, 5 grams freshly ignited 
lime, and o.i gram metallic sodium . 
i gram magnesium, 5 grams freshly ignited 
lime, and 0.25 gram metallic sodium 
i gram magnesium, 5 grams freshly ignited 
lime, and o.n gram metallic lithium 


2OI .O 
196.0 
169.0 


287.0 
326.2 
228.0 



Ignited lime with metallic sodium alone absorbed no nitrogen 
whatever, and only very slight absorption is effected by barium 
carbide alone, barium carbide and potassium, barium fluoride 
and sodium, or amorphous boron and silicon. It is possible that 
the barium carbide used in these experiments decomposed 
partially when it was pulverized. 

From these experiments it appeared that, of the substances 
tried, the best absorbent for nitrogen is a mixture of one part by 
weight of finely powdered magnesium with five parts by weight 
of freshly ignited lime in pieces about as large as poppy seeds, 
and 0.25 part by weight of metallic sodium. The magnesium 
should be intimately mixed with the ignited lime, but it is 
sufficient to add the sodium in the form of a number of pieces 



PROPERTIES OF THE VARIOUS GASES 209 

each about half as large as a pea. The layer of oxide covering 
the metallic sodium should first be removed, and the metal 
should be added to the .mixture just before using. 

The "analytical absorbing power" of the mixture, based upon 
the amount of the magnesium, is 8.15 cc. 

Magnesium and lime react to form metallic calcium. Since 
the above experiments were made, metallic calcium has come 
upon the market, and this may now be used directly for the 
removal of the nitrogen, instead of being formed within the 
apparatus by the interaction of magnesium and lime. Metallic 
calcium energetically combines with nitrogen forming calcium 
nitride, Ca 3 N 2 . 

The researches of Franz Fischer 1 have demonstrated that 
calcium carbide may be employed for the absorption of nitrogen 
and also for the simultaneous removal of oxygen. 

To remove nitrogen from a mixture of this gas with the gases 
of the argon group, the gas mixture, after having been freed 
from other constituents, may be driven backward and forward by 
means of mercury through a heated tube containing one or 
another of the above absorbents. Constant raising and lower- 
ing of the mercury level-bulbs is, however, a tedious procedure, 
and for this reason, if any appreciable amount of nitrogen is to 
be removed, it will be found convenient to employ the Travers 2 
modification of the automatic device described by Collie. 3 
By means of this apparatus the gases can automatically be 
driven through the absorption apparatus in a continuous current. 
Fig. 82 shows an arrangement of the apparatus substantially 
in the form recommended by Travers except that the bulb reser- 
voir is here replaced by a two-neck Wolff bottle with a tubulure 
at the bottom, and an iron tube containing metallic calcium is 
used in place of a glass tube filled with magnesium turnings. 
A small Wolff bottle, A, that has two necks and a tubulure at 

1 Berichte der deutschen chemischen Gesellschaft, 41 (1908), 2017. 

2 Experimental Study of Gases, 101. 

3 J.. Chem. Soc., 55 (1889), no. 



210 



GAS ANALYSIS 



the bottom is connected with the level-bulb B by means of enam- 
elled rubber tubing. Into the two necks of the Wolff bottle are 
inserted, by means of rubber stoppers, two glass tubes, one with 
a two-way stopcock and the other with a single stopcock. The 
tube D is bent as shown in the figure and is provided with a 
small bulb S for catching any mercury that may be carried up 



& 


f Soda p n 
JGuSCuO" Lime h a u s 
afj n c~ i^J Ji-^ P ^irjft> 


fpr 


i j 


U b 


Calcium i 
dMrfjr iD-rf-fr-x 


, frr 


~G^ J ' :: H ...:..."Pn\ 






FIG. 82 

through D. The apparatus may be connected with a mercury 
air pump through the side-arm T. The end of D is connected 
by rubber tubing, securely wired m place, with the tube E of 
Jena glass containing partially reduced copper oxide, and the 
tube F containing soda lime and phosphorus pentoxide. The 
tube G is connected with the tube H which is of iron, and is 
about 1.5 meter long and about 2 cm. inner diameter. U is filled 



PROPERTIES OF THE VARIOUS GASES 211 

with pieces of metallic calcium, or, if this not available, with 
the mixture of magnesium, freshly ignited lime and metallic 
sodium recommended by Hempel. *E and H rest in combustion 
furnaces. The metallic copper is used for the removal of any 
oxygen that might be present in the gas mixture. The cop- 
per oxide serves to oxidize hydrogen and carbon monoxide. 
Hydrogen may result from the action of water vapor upon 
the metallic calcium. The carbon monoxide may diffuse into 
the apparatus through the hot iron tube. To avoid this 
last mentioned difficulty Franz Fischer and Hahnel 1 suggest 
that the iron tube be surrounded by sheet copper 2 mm. 
thick. 

The further ends of F and H are connected with the Collie 
apparatus in the manner shown in the figure. To prepare the 
apparatus for use the level-bulb B is raised and mercury is 
forced up to the stopcock N and through the stopcock M to 
the end of the branch tube C, and M and N are then closed. 
C is now connected with the gasometer containing the gas 
mixture to be treated, M is opened, B is lowered and the gas 
is drawn into the bottle A. M is then closed. The stopcocks 
O and P are also closed, the tubes F and H are heated and the 
apparatus is exhausted through T by means of a mercury pump 
until gases cease to be given off. T is then closed and M is care- 
fully turned to such a position that A communicates with D, 
N is next opened and then the stopcock P. Mercury from the 
reservoir K now drops down through the capillary tube V carry- 
ing with it gas into L and forcing the gas through H. The stop- 
cock O is turned so that mercury flows from L into R in a steady 
stream. R is provided with a side capillary tube W which con- 
nects with the tube /, this latter tube dipping into the mercury 
in the reservoir K. The upper end of the tube / is connected 
through Z with a water suction pump. A twisted piece of rusty 
iron wire is inserted in the lower end of the capillary tube W to 
prevent the mercury that flows into R from L from completely 
1 Berichte der deutschen chemischen Gesdlschaft, 43 (1910), 1436. 



212 GAS ANALYSIS 

closing the capillary. This results in the mercury being drawn 
up through W in a series of fine drops which fall into the reser- 
voir K. In this manner the gases are continuously forced 
through H and A and back through D, E and F, and the proc- 
ess will run for hours without attention if the iron wire was 
properly adjusted and the flow of mercury was carefully regu- 
lated at the beginning of the experiment. 

Further amounts of the original gas mixture may be intro- 
duced through C when desired. After all of the gases except 
those of the argon group have been removed, the gas mixture 
remaining in the apparatus may be pumped out through T by 
means of a Topler pump, and collected as described on page 13, 
or the stopcock N may be closed, and such of the gas residue 
as is in A may be driven out through C into a suitable container 
by raising the level-bulb B and turning the stopcock M into the 
proper position. 

For the removal of large amounts of nitrogen from the air 
Franz Fischer and Ringe l have employed commercial calcium 
carbide. This substance reacts at high temperatures with ni- 
trogen with the formation of calcium cyanamide and the separa- 
tion of carbon, according to the equation, 

CaC 2 + N 2 = N = C - N = Ca + C. 

They find that this reaction does not reverse at a temperature of 
about 800, and that both nitrogen and oxygen may quantita- 
tively be removed by this means. The calcium carbide is placed 
in a thick-walled iron cylinder of sufficient size to hold about 
seven kilograms of the carbide. The operation is conducted in 
a manner essentially similar to that already here described, 
except that the circulating device differs from that employed 
by Collie and Travers. 

1 Berichte der deutschen cliemischen Gesellschaft, 41 (1908), 2017. 



PROPERTIES OF THE VARIOUS GASES 



213 



GASES OF THE ARGON GROUP 





ft 


3 W 


*j .; 


"rt tj 


s- s i 


4 







ii'l 


||| ^ 


u g 

IS 


111 


8:3 






^a a 


<^a^ 


u l 


3 


if 


Helium . 


1.98 




4-5 


5 


2.3 


0.000056 


Neon 


9-97 


20 


30 


53 


29. 


o . 00086 


Argon . 


19-95 


83-4 


87 


156 


52.9 


1 .3 


Krypton . . 


4i-5 


104 


121 


211 


54.3 


0.028 


Xenon . . . 


65-35 


133 


I6 4 


288 


57-2 


0.005 



NITROUS OXIDE 

Properties of Nitrous Oxide. Specific gravity, 1.5229; 
weight of one liter, 1.9688 grams. 

Nitrous oxide is quite soluble in water. One volume of water 
dissolves, at 760 mm. pressure and 20, 0.670 volume (Carius). 

The coefficient of absorption is 

1.30521 o.o45362t + 0.0006843^. 
For alcohol it is 

4.17805 0.06981 6 / + 0.000609 t z , 

and i volume of alcohol takes up at 20 3.0253 volumes N2O. 

Detection of Nitrous Oxide. No satisfactory method has 
yet been devised for the detection of small amounts of nitrous 
oxide. Lunge has proposed 1 that the gas mixture under exami- 
nation be passed through absolute alcohol in which nitrous 
oxide is quite readily soluble while the other gases with which 
it is usually associated are not appreciably dissolved. The 
method serves merely to concentrate the nitrous oxide and 
cannot be regarded as a means of its identification. 

1 Berichte der deutschen chemischen Gesellschaft, 14 (1881), 2188. 



214 GAS ANALYSIS 

The procedure suggested by Hempel 1 is similar in character, 
the gases being condensed by means of liquid air and then frac- 
tionally distilled. This yields a residue rich in nitrous oxide, 
in which the presence of the gas is indicated by the increase 
in volume that results when it is dissociated by mixing with it 
oxyhydrogen gas and exploding the mixture. 

Determination of Nitrous Oxide. For the determination 
of nitrous oxide a variety of methods has been proposed. Wag- 
ner 2 passes the gas over a hot mixture of chromium oxide and 
sodium carbonate. The nitrous oxide is reduced to nitrogen, 
while any nitric oxide that may be present is unaffected. The 
amount of nitrous oxide may be calculated from the volume of 
nitrogen set free, or from the amount of sodium chromate that 
is formed. 

Von Dumreicher 3 burns the gas with hydrogen in a eudiometer. 
Water and nitrogen are formed, and the latter is measured. 
Hempel recommends 4 this method but adds oxyhydrogen gas 
also. He uses his explosion pipette for the combustion and 
finds that the results are satisfactory if the volume of hydrogen 
is two to three times that of the nitrous oxide and if, further, 
such an amount of oxyhydrogen gas is added as will give 26 to 64 
volumes of combustible gas to every 100 volumes of incom- 
bustible gas. The decrease in volume is equal to the volume of 
nitrous oxide. 

N 2 O + H 2 = N 2 + H 2 O 

Von Knorre and Arndt 5 pass a mixture of nitrous oxide and 
hydrogen through a hot Drehschmidt capillary tube (see p. 154) 
and obtain satisfactory results. They also find that this method 
gives approximately accurate results in the analysis of a mix- 

1 Zeitschrift fur Elektrochcmie, 12 (1906), 600. 

2 Zeitschrift fiir analylische Chemie, 21 (1882), 374. 

3 Kais. Akad. d. Wissen. Wien. 82 (1881), 560. 

4 Berichte der deutschen ckemischen Gesellschaft, 15 (1882), 903. See also Ze.il. jut 
Elccktrochemie, 12 (1906), 600. 

5 Berichte der deutschen chemischen Gesellschaft, 32 (1899), 2136; 33 (1900), 30. 



PROPERTIES OF THE VARIOUS GASES 215 

ture of nitrous oxide and nitric oxide. An excess of hydrogen 
is added to the gas mixture and the gases are then slowly passed 
through a Drehschmidt capillary tube heated to bright redness. 

2 NO + 2 H 2 = N 2 + 2 H 2 O 

Too rapid passage of the gas will cause the formation of some 
ammonia from the nitric oxide. 

2 NO + 5 H 2 = 2 NH 3 + 2 H 2 O 

The volumes of the two oxides of nitrogen in the gas mixture 
may be calculated from the contraction. If V = the volume 
of the gas mixture, and C = the contraction, then 

V = vol. N 2 O* + vol. NO, 
C = vol. N 2 O + i J vol. NO, 

and from the foregoing 

vol. NO = 2 (C - V). 
If nitrogen also is present, then 

V = vol. N 2 O + vol. NO + vol. N 2 
C = vol. N 2 O + i l / 2 vol. NO 
vol. H 2 = vol. N 2 O + vol. NO, 

from which it follows that 

vol. N 2 O = 3 vol. H 2 - 2 C 
vol. NO = 2 (C - vol. H 2 ) 
vol. N 2 = V - vol. H 2 . 

JBaskerville and Stevenson l determine nitrous oxide by pass- 
ing the gas over hot copper, reducing the copper oxide by hydro- 
gen, and collecting and weighing the water that is formed. They 
carry out the method as follows: The hydrogen is generated in 
a Kipp apparatus from zinc and sulphuric acid (i :6) to which 

1 Jour. Ind. and Eng. Chem., 3 (1911), 579. 



216 GAS ANALYSIS 

two drops of chloroplatinic acid have been added. The gas is 
passed through solid sodium hydroxide and a long tube filled 
with calcium chloride to remove acid gases and moisture. The 
calcium chloride tube is connected to a combustion tube of hard 
glass that is 100 cm. long and is filled for 70 cm. of its length 
with snugly fitting rolls of copper gauze. The further end of the 
combustion tube is drawn out to fairly small diameter, and the 
end is inserted into a tube filled with calcium chloride, the joint 
between the two being made air tight with a piece of rubber 
tubing. A second tube filled with calcium chloride is joined to 
the first and to the further end of this tube there is connected a 
delivery tube that dips into water or some other liquid in a test 
tube and serves to show the speed of flow of the gas. The com- 
bustion tube rests upon an iron trough in a combustion furnace. 
Hydrogen is now passed through the combustion tube until 
most of the air has been expelled. The tube is then heated to 
dull redness and the passage of hydrogen is continued until the 
copper is completely reduced. The tubes containing calcium 
chloride are weighed and are now connected to the combustion 
tube in the manner above described. The hydrogen is then dis- 
continued and about 800 cc. of the gas sample is passed into the 
tube that contains sodium hydroxide and through the rest of the 
apparatus, the speed of flow of the gas being about two bubbles 
per second. The volume of the gas sample and its temperature 
and pressure are noted before the gas is passed through the ap- 
paratus. To insure complete decomposition of the nitrous 
oxide by the hot copper the operation should be so conducted 
that the last 15 cm. of copper gauze undergoes no oxidation. 
After the sample of gas has been passed through the chain, 
hydrogen is again admitted to the apparatus and is passed 
through it at the rate of from three to four bubbles per second 
until the copper oxide that has been formed is entirely reduced, 
and the water is completely driven out of the tube and into the 
weighed tubes containing calcium chloride. The operation is 
then presumably completed, although the authors give no 



PROPERTIES OF THE VARIOUS GASES 217 

further details, by discontinuing the heating of the combustion 
tube and, when the apparatus is cold, passing dry air through 
the calcium chloride tubes until the hydrogen with which they 
are filled is displaced. They are then weighed and the amount 
of nitrous oxide in the gas sample is calculated from the weight 
of water that has been formed. 

The method cannot be used for the determination of nitrous 
oxide in gas mixtures that contain other oxides of nitrogen or 
oxygen or other gases that would be decomposed by the metallic 
copper with the formation of copper oxide, unless the amounts of 
these gases are determined and the water that results from them 
is subtracted from the total amount of water found. Baskerville 
and Stevenson find that these gases are not present in the 
samples of commercial compressed nitrous oxide that they 
analyzed. 

NITRIC OXIDE (NO) 

Properties of Nitric Oxide. Specific gravity, 1.0378; 
weight of one liter, 1.3417 grams. 

Nitric oxide is but slightly soluble in water, one volume of 
water dissolving only about ^ volume of the gas. It is more 
soluble in alcohol, the coefficient of absorption for temperatures 
between o and 25 being, according to Carius, 

0.31606 0.003487 t + 0.000049 t 2 * 

Nitric oxide cannot be kept over water without undergoing 
change. Nitrous acid is formed together with some hyponitrous 
acid which breaks down partly into nitrous oxide and partly 
into ammonia. The latter then reacts with the nitrous acid and 
liberates nitrogen, which accounts for the presence of this gas in 
quite large amount in nitric oxide that has been stored over 
water for a considerable length of time. 

Nitric oxide is absorbed by solutions of ferrous salts, potassium 
permanganate, potassium dichromate, and alkaline sodium 
sulphite. It is also taken up by concentrated sulphuric acid, 



218 GAS ANALYSIS 

one cc. of this acid of 1.84 specific gravity absorbing 0.035 cc - of 
nitric oxide. If the acid has a specific gravity of 1.5, one cc. of it 
will absorb 0.017 cc * f the gas. 

Hydrogen dioxide reacts with nitric oxide to form nitric acid 
and water. 

Detection of Nitric Oxide. A delicate method for the de- 
tection of nitric oxide consists in passing the gas, mixed with air, 
through a dilute solution of the hydroxide of either sodium or 
potassium and adding Griess's reagent. The reactions that take 
place in the absorption are, according to Le Blanc, 1 as follows: 

2 NO + O 2 >> 2 NO 2 , 

NO + NO 2 - N 2 O 3 , 

NO 2 + absorbent > nitrate and nitrite, 

N 2 0s + absorbent > nitrite. 

The nitrite that has thus been formed in the absorbent is 
detected by first adding acetic acid to the sodium hydroxide or 
potassium hydroxide until the solution has a faint acid reaction 
and then adding Griess's reagent as improved by Ilosvay 2 and 
Lunge. 3 The reagent in this modified form is prepared as 
follows: 0.5 gram of sulphanilic acid is dissolved in 150 cc. of 
dilute acetic acid, o.i gram of solid a-naphthylamine is boiled 
with 20 cc. of water, the colorless solution is poured off from the 
violet residue and to the solution 150 cc. of dilute acetic acid is 
added. The two solutions are then mixed and the reagent is 
kept in a tightly stoppered bottle. 

Lunge states that the reagent is not at all affected by the 
light. This is contradicted by Reckleben, Lockemann and 
Eckardt 4 who state that even in diffused daylight the reagent 
soon takes on a yellowish-red color which renders the detection 
of small amounts of nitrous acid impossible. They find that if 

1 Zeit. fur Elektrochemie, 12 (1906), 541. 
*Bull. soc. chim. (3), 2 (1889), 347. 

3 Z.f. angew. Chem., 1889, 666. 

4 Z.f. analyt. Chem., 46 (1907), 671. 



PROPERTIES OF THE VARIOUS GASES 219 

the solution is kept in the dark it remains completely clear and 
colorless for months. 

In making the test the acidified solution of the absorbent is 
warmed to about 80 and about one-fifth of its volume of the 
Griess's reagent is added. If nitric oxide was present in the gas 
mixture, the solution turns red. The reaction is extremely 
delicate, one part of nitrous acid in one thousand million parts 
of the solution giving a distinct red coloration after one minute. 

Determination of Nitric Oxide. Nitric oxide may quanti- 
tatively be determined by absorption of the gas with a solution 
of ferrous sulphate. The reagent contains one part by weight 
of the salt dissolved in two parts by weight of water, and it is 
very slightly acidified with dilute sulphuric acid. It is used in 
a Hempel double pipette for liquid reagents. The analytical 
absorbing power of this solution 15-2.5. This reagent, however, 
tends to give up the absorbed nitric oxide to indifferent gases, 
and the method does not yield correct results when nitrous oxide 
is present with the nitric oxide. 

It has been proposed to determine nitric oxide by mixing it 
with hydrogen and burning the mixture in a Drehschmidt cap- 
illary tube (see under Nitrous Oxide) . Moser, who has recently 
made a careful comparison of the various methods for the deter- 
mination of this gas states 1 that this method does not yield uni- 
form results both because of the secondary reaction which causes 
the formation of ammonia and because of the porosity of red- 
hot platinum to gases. 

The absorption of nitric oxide by sodium sulphite is original 
with Divers, 2 who, however, gives no details concerning the 
preparation of this solution further than to say that it is "a 
strong solution of either sodium or potassium sulphite to which 
a little alkali hydroxide has been added." He states that it 
" quickly absorbs every trace of nitric oxide, which it fixes in 
the form of hyponitrososulphate, Na2N202SOa." 

1 Z.f. analyt. Chem., 50 (1911), 401. 
*Jour. Chem. Soc., 75 (1899), 82. 



220 GAS ANALYSIS 

Moser finds that this reagent is not superior to ferrous sul- 
phate and that the absorption by sodium sulphite takes place 
quite slowly and is complete only after long shaking. 

A satisfactory titrimetric method for the determination of 
nitric oxide is that based upon the reaction between the gas 
and an acidulated solution of potassium permanganate. 

10 NO + 6 KMnO 4 + 9 H 2 SO 4 = 

3 K 2 SO 4 + 6 MnSO 4 + 10 HNO 3 + 4 H 2 O. 

The reaction was first examined by Terreil 1 who found that 
nitric oxide is completely oxidized to nitric acid by a neutral 
or an acidified solution of potassium permanganate, while 
nitrous oxide is not attacked. Lunge 2 ascertained that the 

speed of reaction between nitric oxide and a y~ solution of po- 
tassium permanganate is so slight that complete absorption 
of the gas is attained only when an apparatus that brings about 
prolonged and intimate contact between the gas and absorbent 
is employed. He recommends for this purpose the ten-bulb 
tube shown on page 359, but better results will undoubtedly 
follow the employment of a Friedrichs spiral gas washing bottle, 
page 123. Before beginning the determination the air in the 
apparatus must be displaced by carbon dioxide because of the 
reaction between nitric oxide and oxygen. To avoid this opera- 
tion and also to obtain more complete absorption, Moser 3 
suggests that the gas mixture be passed into a spiral absorption 
bulb that is made entirely of glass and that is figured in his arti- 
cle. A simple and satisfactory substitute for this spiral bulb 
may be made by fusing to one of the tubes of the bulb of a Hem- 
pel gas pipette of about 130 cc. capacity a capillary tube about 
3.5 cm. long, and to the other tube of the bulb a piece of glass 
tubing about i cm. external diameter and 20 cm. long. The bulb 
is placed in a clamp with the short capillary tube uppermost, 

1 Complex rendus, 63 ( 1 866) , 970. 

2 Z.f. angew. Chem., 1890, 567. 

3 Loc. cit. 



PROPERTIES OF THE VARIOUS GASES 221 

and the long stem is inserted into a wide mouth bottle of about 
250 cc. capacity in which is placed a measured volume (about 
200 cc.) of the standardized solution of potassium permanganate. 
The potassium permanganate is approximately ' decinormal in 
strength and to every 100 cc. of the solution is added from 30 to 
50 cc. of 2 N sulphuric acid. The capillary tube of the bulb is 
closed by a short piece of rubber tubing and pinchcock. A water 
suction pump is connected to this tube, and the permanganate 
solution is drawn up until it fills the tube and reaches nearly to 
the top of the capillary tube. The gas burette containing the 
sample of gas under examination is connected with the bulb 
by means of the usual piece of bent capillary tubing and the 
gas sample is passed over into the bulb. The pinchcock at the 
top of the bulb is then closed and the bulb is disconnected from 
the burette. The bottle is grasped in the left hand and the lower 
tube of the bulb in the right hand, and with the end of the large 
tube of the bulb resting upon the bottom of the bottle, the bulb 
is shaken for about ten minutes to effect complete reaction .be- 
tween the nitric oxide and the potassium permanganate. The 
pinchcock at the top of the bulb is then opened and the solu- 
tion is allowed to run out of the bulb down into the bottle, the 
bulb being finally rinsed with distilled water. An excess of a 
standardized solution of ferrous sulphate is added to the po- 
tassium permanganate and the excess of ferrous sulphate is 
titrated back with potassium permanganate. 

The results by this method even when the Moser absorption 
bulb is employed are somewhat lower than those obtained by 
absorption with ferrous sulphate, which Moser ascribes to the 
reaction between the nitric oxide and the oxygen dissolved in 
the solution of potassium permanganate. 

Schonbein l found that when nitric oxide was brought into 
contact with an excess of hydrogen dioxide the gas is oxidized to 
nitric acid: 

2 NO + 3 H 2 O 2 = 2 HN0 3 + 2 H 2 O 

1 /./. prakt. Chem., 81 (1860), 265. 



222 GAS ANALYSIS 

The applicability of this reaction to the determination of 
nitric oxide has been studied by Davis, 1 by Wilfarth 2 and by 
Lunge. 3 Lunge discarded the method because his experiments 
indicated that the absorption of nitric oxide by hydrogen dioxide 
either in acid or in alkaline solution was not complete. Moser 4 
found that this criticism is correct when the method is carried 
out in the manner described by Wilfarth and by Lunge, but 
he states that with the absorption bulb that he devised it is 
possible to obtain complete oxidation of nitric oxide in from six 
to twelve minutes. He employs as absorbent a three per cent 
solution of hydrogen dioxide in a definite volume of which (about 
no cc.) the free acid is first determined by titration with a stan- 
dardized solution of potassium hydroxide, using a one per cent 
solution of phenolphthalein as indicator. The reagent is then 
brought into the absorption bulb, the gas is passed in from a 
gas burette, and the gas and hydrogen dioxide are shaken to- 
gether for several minutes. The absorbent is then transferred 
to a beaker and the nitric acid that has been formed is titrated 
with potassium hydroxide. If acid or alkaline gases are present 
in the gas mixture under examination they must first be re- 
moved by passing the mixture through suitable absorption ap- 
paratus. Under such conditions, however, the determination of 
the nitric oxide with potassium permanganate is preferable to 
that with hydrogen dioxide. 

Determination of Nitrites in the Atmosphere. The method 
of Ilosvay and Lunge for the detection of nitrites may also be 
employed for the determination of nitrites in the atmosphere. 
A measured amount of air is drawn through a solution of sodium 
hydroxide or potassium hydroxide and the color that results 
when Griess's reagent is added under the conditions above pre- 
scribed is compared with the color yielded by a standard ni- 
trite solution. For approximate work the standard solution 

1 Chemical News, 41 (1880), 188. 
2 Z.f. analyt. Chem., 23 (1884), 587. 

3 Z.f: angew. Chem., 1890, 568. 

4 Loc. cit. 



PROPERTIES OF THE VARIOUS GASES 223 

may be prepared by dissolving a weighed amount of either 
potassium nitrite or sodium nitrite in water. If greater accuracy 
is desired the standard nitrite solution may be prepared by pre- 
cipitating a solution of silver nitrate with sodium nitrite, re- 
crystallizing the silver nitrite twice from hot water and then 
adding to its solution in hot water sodium chloride, and remov- 
ing the precipitated silver chloride by filtration. 

NITROGEN TETROXIDE 

Properties of Nitrogen Tetroxide. Specific gravity (NO 2 ), 
1.5906. Weight of one liter (NO2), 2.0563 grams. The mole- 
cule of nitrogen tetroxide is considered to have the formula N2O4 
at temperatures below 11 and to dissociate into NO2 as the 
temperature rises. At the average temperature of the laboratory 
the gas will contain both the simpler molecule NC>2 and the 
polymer ^64. 

When brought into contact with water, nitrogen tetroxide 
forms nitric acid, nitrous acid and nitric oxide, according to 
the equations 

ON-ON0 2 + H 2 = HONO 2 + HO-NO, 
3 ON-ONO 2 + 2 H 2 = 4 HONO 2 + 2 NO. 

When nitrogen tetroxide is passed through a dilute solution of 
sodium hydroxide, oxygen or air being absent, sodium nitrite 
and nitrate are formed l in the proportions shown in the first 
equation above. If, however, oxygen or atmospheric air is 
present with the nitrogen tetroxide, some of the nitrite is oxidized 
to nitrate. The gas is rapidly absorbed by concentrated sul- 
phuric acid (1.7 to 1.8 sp. gr."), nitrosyl sulphuric acid and nitric 
acid being formed. 

ON-0-NO 2 + S0 2 (OH) 2 = S0 2 (OH) (ONO) + HO-NO 2 

1 Lunge and Berl, Z.f. angewandte Chem., 19 (1906), 857. 



224 GAS ANALYSIS 

Nitrogen tetroxide may be detected by absorbing the gas 
in a dilute solution of sodium hydroxide, acidifying this with 
acetic acid and adding Griess's reagent. (See under Nitric 
Oxide.) 

AMMONIA (NH 3 ) 

Properties of Ammonia. Specific gravity, 0.5895; weight 
of one liter, 0.7621 gram. One gram of water absorbs, at a 
pressure of 760 mm., 

at o, 0.875 gram (1129 cc.) 
" 10, 0.679 " ( 876 " ) 

" 20, 0.526 * ( 6 7 8 " ) 

Alcohol and ether also absorb considerable quantities of the 
gas. 

Detection of Ammonia. Ammonia may be detected when 
present in fairly large amounts by means of litmus paper or 
turmeric paper. A more sensitive reagent for the detection of 
minute amounts of ammonia is Nessler's reagent which is an 
alkaline solution of potassium mercuric iodide, K^Hgl^ When 
ammonia acts upon this solution mercurammonium iodide 



N=Hg 
M 

is formed. If the amount of ammonia is appreciable, the com- 
pound appears as a reddish brown precipitate. With smaller 
amounts of ammonia it imparts merely a yellow color to the 
solution. The reaction is very delicate; 0.05 mg. of ammonia in 
one liter of water can readily be detected. 

Determination of Ammonia. Ammonia may be determined 
by passing the gas mixture through a measured amount of dilute 
hydrochloric or sulphuric acid of known strength and titrating 
the excess of acid with a standard solution of an alkali, using 
litmus or methyl orange as indicator. 



PROPERTIES OF THE VARIOUS GASES 225 

If the amount of ammonia in the gas mixture is very small, as 
for example in atmospheric air, the ammonia may be absorbed 
by passing it through ammonia-free distilled water slightly 
acidified with sulphuric acid and then determining the ammonia 
colorimetrically with Nessler's reagent. 

CARBON DIOXIDE (C0 2 ) 

Properties of Carbon Dioxide. Specific gravity, 1.5201; 
weight of one liter, 1.9652 grams. 

According to Naccari and Pagliani one volume of water ab- 
sorbs, between 17 and 27, 

1.5062 0.036511 / -+- 0.0002917 / 2 . 

One cc. of sulphuric acid (sp. gr. = 1.78) dissolves, at 14 C. 
and 816.4 mm - pressure, 1.16 cc. of carbon dioxide. 

Carbon dioxide is readily absorbed by a solution of potassium 
hydroxide or of barium hydroxide. 

Determination of Carbon Dioxide. For the volumetric de- 
termination of the gas, a solution of one part of caustic potash 
in two parts of water is employed. The analytical absorbing 
power of this solution is 40. For the rapid and approximate 
determination of carbon dioxide by means of this absorbent, 
the Honigmann gas burette (page 7 2) may be used. With the 
Bunte gas burette (page 74) somewhat - more accurate results 
can be obtained. 

The most satisfactory forms of absorbing apparatus for use in 
technical gas analysis are the spiral pipette described on p. 81 
or the Hempel simple pipette for solid and liquid reagents 
(Fig. 35). With the latter the cylindrical part C is first closely 
filled with very short rolls of iron wire gauze. The gauze has 
a mesh of i to 2 mm., and the rolls are from i to 2 cm. long and 
about 5 mm. thick. The high viscosity of the reagent causes 
it to cling to the wire gauze when the gas is passed into the pi- 
pette and, as a consequence, the absorption of the carbon 



226 GAS ANALYSIS 

dioxide is very rapid. The viscosity of the reagent serves also 
to protect the iron wire gauze from oxidation by any oxygen 
in the gas mixture. Unless the amount of carbon dioxide in a 
gas mixture is unusually high, it is quantitatively removed by 
simply passing the gas once into either pipette and allowing it 
to remain there a few seconds. 

Special methods for the determination of small percentages 
of carbon dioxide such as are found, for example, in atmospheric 
air are described in Chapter XVIII. 

CARBON MONOXIDE (CO) 

Properties of Carbon Monoxide. Specific gravity, 0.9673 ; 
weight of one liter, 1.2506 grams. One volume of water dis- 
solves, according to L. W. Winkler, 

at o, 0.03537 vo1 - of CO 
" 10, 0.02816 

" 20, 0.02319 " 

According to Carius, alcohol dissolves, between o and 25, 
0.20443 volume of carbon monoxide. 

Detection of Carbon Monoxide by Blood Spectrum. The 
most delicate and dependable method for the detection of carbon 
monoxide is that in which the gas is absorbed by a solution of 
blood and the resulting carbon monoxide haemoglobin is de- 
tected by the spectroscope. When a dilute solution of pure 
blood is brought before the slit of the spectroscope, two absorp- 
tion bands, lying between the Fraunhofer lines D and E, are 
seen (Fig. 83, spectra No. i and No. 2). If, now, a reducing 
agent, such as ammonium sulphide, is added to the blood solu- 
tion, these two bands, which are due to the oxyhaemoglobin of 
the blood, disappear and are replaced by a single broad and 
weakly denned band (spectrum No. 4). 

When, however, carbon monoxide has previously been 
brought into contact with the blood solution, the two absorption 



PROPERTIES OF THE VARIOUS GASES 



227 



bands due to carbon monoxide haemoglobin (spectrum No. 3) 
do not disappear when the reducing agent is added. Conse- 
quently the persistence of these two separate absorption bands 
is conclusive proof of the presence of carbon monoxide in the 
gas mixture under examination. 

The solution of blood for use in this test is prepared by freeing 
a sample of blood from fibrin by beating it with a bundle of 
straws and then diluting the clear blood with an equal volume 
of a cold, saturated solution of borax. The addition of borax 

BC D Eb F G 

Pure blood highly diluted 



Blood highly diluted + CO 

Blood highly diluted 

+ NH 4 SH 




FIG. 83 



prevents putrefaction and does not change the spectroscopic 
properties of the blood, reduction and combination with oxygen 
and carbon monoxide taking place just as readily as if fresh 
blood or a solution of haemoglobin were employed. The solu- 
tion used in the absorption of carbon monoxide is prepared from 
the concentrated solution by mixing one cc. of the latter with 
19 cc. of water. This gives a blood solution of the concentration 
i in 40. The absorption of carbon monoxide by this dilute 
blood solution may be effected by filling a 100 cc. bottle with 
water, emptying it in the room of which the air is to be tested 
for carbon monoxide, introducing 3 cc. of the dilute blood 
solution into the bottle, inserting the stopper in the bottle and 
then thoroughly shaking the bottle to bring the blood into con- 
tact with the inclosed gas. A more efficient absorption appa- 
ratus is that designed by Wolff 1 (Fig. 84). In preparing this 

1 Correspondenzblatt des Vereins analytischer Chemiker, 3 (1880), 46. 



228 



GAS ANALYSIS 



apparatus for use a small wad of glass wool is inserted into d 
from above and gently pressed into place. The tube is then 
filled up to / with moderately fine, powdered glass. The grains 
of glass should be about as large as those of ordinary gunpowder 
and before its introduction into the tube the glass should be 
thoroughly cleaned by boiling it with hydrochloric acid, and 
washing it with distilled water. Two cc. of the dilute blood 
solution (i in 40) is then introduced through a from a pipette. 

a is closed and by gen- 
tly blowing into h the 
blood solution is caused 
to uniformly distribute 
itself throughout the 
column of powdered 
glass. The side tube e 
is now connected with 
the gas mixture (air) 




that is to be tested for 
carbon monoxide, and 
the gas is driven or 
drawn through the ab- 
sorption tube, its vol- 
ume being measured 
by a gas meter or 
other suitable device 
attached to h. To pre- 
vent the evaporation of 

the water from the blood solution in the absorption apparatus, 
it is advisable to insert between e and the source of gas a 
U-tube or wash bottle containing sufficient water to keep the 
entering air saturated with moisture. If only very small 
amounts of carbon monoxide are to be expected, a sample of air 
of about 10 liters should be passed through the absorption appa- 
ratus at a rate of about 3 liters per hour. If it is not convenient 
to set up the apparatus in or near the room whose atmosphere 



FIG. 84 



PROPERTIES OF THE VARIOUS GASES 229 

is to be tested, the sample may be collected in a 10 liter bottle 
by filling the bottle with water and emptying it in the room. 

After the absorption of carbon monoxide by the blood solu- 
tion has been accomplished in either of the two ways above 
described, it is transferred to a small test tube and examined 
with a spectroscope. If the Wolff absorption tube has been 
used, the blood solution is removed after the test by taking 
out the stoppers a and c, placing the test tube under c, and 
slowly dropping pure water upon the powdered glass. The 
liquid is collected in the test tube until the volume amounts 
to 3 cc. Since 2 cc. of the dilute blood solution (i in 40) was 
originally used, the resulting 3 cc. of solution would now have 
a concentration of i in 60. 

Any spectroscope of not too great dispersion may of course be 
employed for the examination of the blood spectrum, but a 
small direct vision spectroscope is quite as satisfactory for this 
purpose as a larger one. For checking the result of the spec- 
troscopic examination a second small test tube should be filled 
with the original blood solution, also diluted to i in 60, that has 
not been exposed to the action of the gas. One drop of a strong 
solution of ammonium sulphide is added to the contents of 
each tube, the tubes are corked and thoroughly shaken, and 
the spectra are examined after the tubes have stood for about 
half an hour. The presence of the two absorption bands 
shown in Fig. 83, spectrum No. 3, in the J)lood solution that has 
been exposed to the gas, and the absence of these bands in the 
solution of pure blood is conclusive proof of- the. presence of 
carbon monoxide in the air under examination. When the test 
is made in this manner the delicacy of the method is about 0.03 
per cent by volume of carbon monoxide. 

Kostin has found l that if the oxygen of the air is first removed, 
the delicacy of the blood test for carbon monoxide is greatly 
enhanced, and that under these conditions one part of the gas in 
forty thousand parts of air may be detected. The removal of 

1 Archivfur die Gesammte Physiologic, 83 (1901), 572. 



230 



GAS ANALYSIS 



oxygen may be effected by passing the air through 3 liters of a 
saturated solution of ferrous sulphate to which i liter of strong 
ammonium hydroxide has been added. The solution is placed 
in an aspirator bottle that is filled with iron wire gauze (A, 
Fig. 85). Four liters of this solution which contains much 
undissolved ferrous hydroxide is able to absorb the oxygen 
contained in 80 liters of air. Two such bottles are employed, 
the air under examination being first drawn into one and then 




FIG. 85 

driven into over the other, and passed backwards and forwards 
between the two aspirators until all oxygen has been removed. 
The residual gas is next forced from one aspirator into the other 
through one of the washing flasks BB' and the absorption ap- 
paratus K containing the blood solution. The washing flasks 
are charged with oxalic acid for the removal of any ammonia 
that may be given off from the material in the aspirator bottles. 
Ogier and Kohn-Abrest remove 1 oxygen by means of a solu- 

1 Ann. chim. analyt. appl., 13 (1908), 218. 



PROPERTIES OF THE VARIOUS GASES 231 

tion of sodium hyposulphite, which is probably more rapid in 
its action and more convenient to handle than is the reagent 
used by Kostin. 

Some investigators are of the opinion that the best method 
for detecting the presence of carbon monoxide in blood is that 
suggested by Kunkel. The blood is here diluted with 10 volumes 
of water and an equal volume of a 3 per cent tannin solution is 
then added. If the blood contains carbon monoxide, a reddish 
precipitate is formed, while with normal blood the precipitate 
is dark brown. These color reactions become especially distinct 
after five or six hours. 

On the other hand, Doepner 1 states that the spectroscopic 
detection of carbon monoxide in blood is fully as satisfactory as 
the best of the precipitation methods. 

Detection of Carbon Monoxide by means of Iodine Pent- 
oxide. Iodine pentoxide and carbon monoxide react on each 
other with the liberation of free iodine and the formation of 
carbon dioxide. 

I 2 O 5 + 5 CO = 2 I + 5 CO 2 

C. de la Harpe and Reverdine 2 first utilized this reaction for the 
detection of carbon monoxide. More recently Levy and Pecoul 3 
find that by passing the liberated iodine into chloroform, minute 
amounts of carbon monoxide in air can be detected. They state 
that one volume of carbon monoxide in 10,000 volumes of air 
will set free sufficient iodine to give to the chloroform an intense 
color. If acetylene is present in no greater proportion than 
i : 10,000, it will cause no coloration of the chloroform, but larger 
amounts of acetylene should be removed before the test is made. 

Determination of Carbon Monoxide by Absorption. For 
the absorption and volumetric determination of carbon monox- 
ide a hydrochloric acid or an ammoniacal solution of cuprous 
chloride is employed. 

1 Z. /. Medizinalbeamte, 22 (1909), 287. 

2 Ghent. Ztg. 12 (1888), 1726. 

3 Comptes rendus, 142 (1906), 162. 



232 GAS ANALYSIS 

The hydrochloric acid solution of cuprous chloride may be 
prepared, according to Winkler, by adding a mixture of 86 
grams of copper oxide and 17 grams of finely divided metallic 
copper to 1086 grams of hydrochloric acid (sp. gr. = 1.124), the 
mixture being slowly introduced and the acid frequently stirred. 
The copper powder is best prepared by the reduction of copper 
oxide with hydrogen. After this mixture has been added to the 
acid, a spiral of copper wire reaching from the bottom of the 
bottle up to its neck is inserted, and the bottle is closed with a 
soft rubber stopper. The solution is dark in the beginning, but 
upon standing it becomes wholly colorless. In contact with the 
air, however, it again turns dark brown, and some cupric chloride 
forms. 

The analytical absorbing power of the solution is 4 cc. of 
carbon monoxide. 

Another method somewhat more rapid and convenient than 
that just described is given by Sandmeyer. 1 

Twenty-five parts of crystallized copper sulphate and 1 2 parts 
of dry sodium chloride are placed in 50 parts of water and heated 
until the copper sulphate dissolves. Some sodium sulphate may 
separate out at this point, but the preparation is continued 
without the removal of this salt. 100 parts of concentrated 
hydrochloric acid and 13 parts of copper turnings are then 
added and the whole is boiled in a flask until decolorized. To 
avoid excessive evaporation it is desirable to insert in the neck 
of the flask a tall condensing tube or an upright condenser. The 
addition of platinum foil to the contents of the flask will facilitate 
reduction. The solution should be kept in bottles that are 
filled up to the neck and are closed by rubber stoppers. 

The ammoniacal solution of cuprous chloride may be prepared 
as follows: 

800 cc. of the hydrochloric acid solution prepared by the 
Winkler method given above or 1200 cc. of the Sandmeyer 
solution is poured into about 4 liters of water, and the resulting 

1 Berichte der deutschen chemischen Gesellschaft, 17 (1884), 1633. 



PROPERTIES OF THE VARIOUS GASES 233 

precipitate is transferred to a graduated stoppered cylinder of 
250 cc. capacity. After about two hours the precipitate and 
liquid which is above the 50 cc. mark is drawn off by means 
of a siphon and 7.5 per cent ammonium hydroxide is added 
up to the 250 cc. mark. The stopper is inserted, the cylinder is 
well^ shaken, and it is then allowed to stand for several hours. 
A solution prepared in this manner has so slight a tension that 
the latter may in nearly every case be disregarded. 

The analytical absorbing power of this solution is 6 cc. of 
carbon monoxide. 

Frischer suggests 1 the preparation of an ammoniacal solution 
of a cuprous salt by adding ferrous sulphate to an ammoniacal 
solution of cupric sulphate, but he gives no specific directions. 

Solutions of cuprous chloride have no considerable tension, so 
that this may be disregarded in analyses in which only approxi- 
mate results are desired. In very exact determinations, however, 
the gases that have been in contact with the reagent must be 
freed from hydrogen chloride or from ammonia. 

The solutions of cuprous chloride may conveniently be used 
in the Hempel double pipettes for liquid reagents (Fig. 36). 

If, after the absorption of carbon monoxide in a gas mixture, 
the hydrogen is to be determined with palladium, the ammonia- 
cal solution must be used. If the amount of carbon monoxide 
alone is to be ascertained, the hydrochloric acid solution may be 
employed with equally good resultSi 

H. Drehschmidt 2 has shown, however, that the union of 
carbon monoxide with cuprous chloride is so feeble that upon 
shaking a solution that has taken up any considerable quantity 
of carbon monoxide, this gas is again given up in an atmosphere 
free from carbon monoxide. For this reason two pipettes are 
used in the absorption, one pipette containing a solution of cu- 
prous chloride that has been in use some time, the other a solution 

1 Chem. Ztg., 32 (1908), 1005. 

2 Berichte der deutschen chemischen Gesellschaft, 2O (1887), 2344, 2752; and 21 
(1888), 2158. 



234 GAS ANALYSIS 

that has been but little used. In the absorption, the gas in 
question is first shaken for two minutes with the first-mentioned 
solution, is drawn back into the burette and is then passed into 
the second pipette containing the but slightly used solution, 
and is shaken three minutes therein. According to Drehschmidt, 
the ammoniacal solution is to be preferred to the hydrochloric 
acid one. 

The results obtained by Gautier and Clausmann 1 in their 
experiments on the removal of carbon monoxide by absorption 
with cuprous chloride demonstrate the necessity of using two 
solutions of cuprous chloride as Drehschmidt recommends, 
and of shaking the gas with the absorbent, and furnish 
convincing evidence of the difficulty of effecting complete 
removal of carbon monoxide in the apparatus of Elliott 
or with the form of absorption pipette customarily employed in 
the Orsat apparatus. Producer gas contains a high percentage 
of carbon monoxide (sometimes as high as thirty per cent) and 
a comparatively small amount of hydrogen. In the analysis of 
such gas mixtures it should be borne in mind that the analytical 
absorbing power of the acid solution of cuprous chloride is only 
4, and of the ammoniacal solution of cuprous chloride only 6, 
and that the absorption of carbon monoxide by either of these 
reagents becomes quite slow even before these limits are reached. 
It is consequently of particular importance that record be kept 
of the volume of carbon monoxide that the absorbent has taken 
up, and that the absorbent be renewed as soon as it has lost its 
efficiency. 

Certain gases other than carbon monoxide are soluble to an 
appreciable degree in solutions of cuprous chloride. This renders 
it necessary, if accurate results are to be obtained, to saturate 
the cuprous chloride solution with those gases that are slightly 
soluble in it before proceeding to the absorption of carbon 
monoxide. 

Solutions of cuprous chloride absorb not only carbon mon- 

1 Compt. rend., 142 (1906), 485. 



PROPERTIES OF THE VARIOUS GASES 235 

oxide, oxygen and acetylene, but also the so-called heavy hydro- 
carbons. For this reason the heavy hydrocarbons, even if their 
determination is not desired, must be removed from the gas mix- 
ture before the carbon monoxide is absorbed by cuprous chloride. 
Failure to do this is a frequent cause of erroneous results. 

Determination of Carbon Monoxide by means of Iodine 
Pentoxide. Nicloux l and Gautier 2 employ the reaction be- 
tween iodine pentoxide and carbon monoxide (see p. 231) for 
the quantitative determination of the latter substance. Kinni- 
cutt and Sanford 3 have shown that this method can be used for 
the determination of very small amounts of carbon monoxide 
not only in air, but also in illuminating gas. The gas mixture 
under examination must first be freed from unsaturated hydro- 
carbons, hydrogen sulphide, sulphur dioxide, and similar reduc- 
ing gases. To accomplish this Kinnicut and Sanford pass the 
gas through two U-tubes, one containing sulphuric acid 4 and 
the other small pieces of potassium hydroxide. 5 The purified 
gas is then passed through a small U-tube containing 25 grams 
of iodine pentoxide. Inasmuch as this substance acts upon 
cork, rubber, and the usual lubricants, Morgan and McWhorter 
later suggested 6 that the iodine pentoxide be placed in a U-tube 
with side arms, and that the large ends of the U-tube be then 
sealed before the blast lamp. The U-tube is suspended in an oil 
bath and its exit tube is joined to a Wolff absorption tube (see 
page 228) containing 0.5 grams of potassium iodide dissolved in 
5 cc. of water. The oil bath is heated to 150 C. The tempera- 
ture should not be allowed to rise much beyond 150 C., for 
Nowicki 7 has found that iodine pentoxide itself begins to de- 

1 Compt. rend., 126 (1898), 746. 
*Ibid., 126 (1898), 931. 

3 /. Am. Chem. Soc., 22 (1900), 14. 

4 It would be preferable to place the sulphuric acid in a Friedrichs spiral gas wash- 
ing bottle (see p. 123). 

5 See also Weiskopf, /. Chem. Met. Soc. S. Africa, g (1909), 258, 306. 

6 J. Am. Chem. Soc., 29 (1907), 1589. 

7 Oesterr. Zeit.f. Berg-HiM, 54 (1906), 6. 



236 GAS ANALYSIS 

compose at 165 and is completely broken down at 300. He 
also states that the oxidation of carbon monoxide by iodine 
pentoxide begins at 45 and is complete at 88. From 250 cc. to 
1000 cc. of the gas mixture under examination is then passed 
through the apparatus at the rate of about one liter in two hours. 
The iodine that is set free in the reaction is absorbed by the 
solution of potassium iodide in the Wolff tube. 

Kinnicut and Sanford determined the amount of carbon 
monoxide in the gas mixture by titrating the free iodine with 
N/IOOO solution of sodium thiosulphate; 0.002266 gram of 
iodine is equivalent to one cc. of carbon monoxide measured 
under standard conditions. 

In the reaction between iodine pentoxide and carbon monox- 
ide, one cc. of carbon monoxide yields one cc. of carbon dioxide 
which in the above method passes through the solution of 
potassium iodide. Morgan and McWhorter 1 recommend that 
as a check upon or substitute for the iodine titration, the liber- 
ated carbon dioxide be determined. This they do by passing the 
gas that issues from the Wolff tube through an absorption 
apparatus 2 containing 50 cc. of a solution of barium hydroxide 
such as is used in the Hesse method for the determination of 
carbon dioxide in air, and determining the volume of the ab- 
sorbed carbon dioxide by titration with a standard solution of 
oxalic acid that contains 1.1265 grams of crystallized oxalic acid 
to the liter. Five cc. of this solution is equivalent to one cc. of 
carbon dioxide measured under standard conditions. Phenol- 
phthalein, one part in 250 parts of alcohol, is used as indicator. 

The above method for the determination of carbon monoxide 
by the use of iodine pentoxide gives very accurate results if the 

1 Loc. cit. 

2 They used a long test tube (24 x 2.5 cm.). This might advantageously be re- 
placed by a glass cylinder about 20 cm. high and 4 cm. internal diameter, fitted 
with a three-hole rubber stopper carrying an inlet and exit tube, and the tip of a 
burette. Such an arrangement would permit of the titration of the solution of 
barium hydroxide without transferring it to another container and thus exposing it 
to the air. 



PROPERTIES OF THE VARIOUS GASES 237 

carbon monoxide is present in quite small amounts. By means 
of it one part of carbon monoxide in 40,000 parts of air may be 
determined in as small an initial volume of air as one liter. It is, 
however, not suited to the determination of large amounts of 
carbon monoxide as Gill and Bartlett have shown l in their 
examination of the method of Smits, Raken and Torwogt 2 who 
had proposed the employment of the method for the determina- 
tion of carbon monoxide in illuminating gas. 

Colorimetric Determination of Carbon Monoxide. Hal- 
dane has devised 3 a colorimetric method for the determination 
of small amounts of carbon monoxide in air. The method is 
based upon the fact that when oxygen and carbon monoxide are 
passed through a blood solution the amounts of oxyhaemoglobin 
and carbon monoxide haemoglobin that are formed are in the 
ratio of the partial pressures of these two gases in the air, multi- 
plied by a constant. The percentage of oxygen in the gas mix- 
ture can easily be determined by analysis, and if the value of 
the constant is known, the percentage of carbon monoxide in 
the gas can then be calculated from the relative amounts of 
oxyhaemoglobin and carbon monoxide haemoglobin that are 
formed in a solution of blood through which the gas mixture 
in question has been passed. 

A dilute solution of oxyhaemoglobin is of a yellow color, while 
that of carbon monoxide haemoglobin is pink. The two solu- 
tions required for the colorimetric determination are (i) A five 
per cent solution of defibrinated blood/ This solution should 
be freshly prepared and should be kept in a stoppered bottle. 
(2) A solution of carmine, which is prepared by grinding one 
gram of carmine with a few drops of ammonium hydroxide in 
a mortar and dissolving the substance in 100 cc. of glycerine. 
Ten cc. of this liquid diluted to one liter with water forms the 
standard solution. 

1 J. Ind. and Eng. Chem., 2 (1910), 9. 

2 Z.f. angew. Chem., 1900, 1002. 

3 /. Physiol., 18 (1895), 461. 



238 GAS ANALYSIS 

The air under examination is drawn through a bottle of 
about 200 cc. capacity fitted with a three-hole rubber stopper. 
In two of the openings of the stopper are inserted the inlet and 
outlet tubes for the passage of the air, and the third is closed 
by a glass plug. After the air originally in the bottle has been 
completely displaced by the air under examination, the rubber 
tubes attached to the glass tubes of the bottle are closed by pinch- 
cocks. The glass rod closing the third opening in the stopper 
is then removed, and there is inserted through this opening 
the tip of a small pipette that contains about five cc. of the 
blood solution. This solution is allowed to run down into the 
bottle, the pipette is withdrawn, the opening in the stopper 
is again closed with a plug, and the flask is gently shaken for 
about five minutes. 

The blood solution is then transferred to a small colorimeter 
tube. In a second colorimeter tube of exactly the same dimen- 
sions, five cc. of the original blood solution is placed, and in a 
third tube five cc. of the blood solution that has been saturated 
with carbon monoxide by shaking the blood with coal gas. 
The standard carmine solution is now run from a burette into 
the second colorimeter tube until the color of the liquid is 
identical with that of the solution that has been saturated 
with carbon monoxide. The carmine solution is then added 
to the contents of the first test tube until the same tint is 
produced. 

If x cc. of the carmine solution were run into a second tube, 
and y cc. into the first tube, then 



x + 5 
X * x zoo = 5, 



y +5 



in which 5 is the percentage saturation of the blood that has 
been shaken with the air under examination. The amount of 
carbon monoxide in the air may then be calculated from the fol- 
lowing table: 



PROPERTIES OF THE VARIOUS GASES 



2 39 



PERCENTAGE SATURATION 


CARBON MONOXIDE IN AIR 


10 


0.015 per cent 


20 


0.04 




30 


0.08 




40 


O.I2 




SO 


0.16 




60 


O.22 




70 


0.30 




80 


O.6O 




90 


1.2 





The method is stated to give fairly accurate results for amounts 
of carbon monoxide in air between 0.015 an d one per cent. With 
more than one per cent of carbon monoxide the gas should be di- 
luted with air that is free from carbon monoxide. 

Determination of Carbon Monoxide by Fractional Com- 
bustion. Nesmjelow 1 has made an exhaustive study of the 
fractional combustion of carbon monoxide in the presence of 
hydrogen and methane. He summarizes the results of his ex- 
periments as follows: 

(1) That when hydrogen mixed with air is passed through a 
U-shaped tube that contains palladium asbestos and stands at 
the temperature of the room, the hydrogen is burned completely 
upon a single passage of the gas mixture through the tube; 

(2) That when a mixture of hydrogen, carbon monoxide and 
air is passed through the U-tube, both the hydrogen and carbon 
monoxide (in the proportions in which he used them) burn com- 
pletely without previous warming of the palladium asbestos. 
It is thus easily possible to determine hydrogen and carbon 
monoxide by combustion over palladium asbestos, and ascer- 
taining the contraction and the volume of carbon dioxide 
formed; 

(3) That the combustion of carbon monoxide under the above 
conditions begins at 1 20, while that of methane does not begin 

1 Z. analyt. Ch., 48 (1009), 232. 



240 GAS ANALYSIS 

below 150, and that if a mixture of hydrogen, carbon monoxide, 
methane and air is passed through the palladium asbestos tube, 
at a speed not exceeding one liter per hour, hydrogen and car- 
bon monoxide will be completely oxidized and methane will 
not be attacked. If the speed of flow of the gas mixture be in- 
creased, the rise of temperature in the U-tube, resulting from 
the more active combustion, may cause some of the methane 
to burn and thus render the results worthless. 

Nesmjelow then describes a method, original with him, for the 
fractional combustion of carbon monoxide by means of copper 
oxide. Copper oxide, mixed with asbestos fibers, is heated to 
dark redness and, after cooling in a desiccator, is placed in a 
small U-tube of hard glass. This is connected at the two ends 
with a gas burette and pipette in the usual manner, and a sand 
bath is then brought up under it and the lower part of the tube 
is covered with the sand. The bath is heated to 250, and the 
mixture of hydrogen, carbon monoxide, methane and air passed 
through it about six times. The sand bath is then removed 
and the gas cooled to the temperature that it had at the begin- 
ning. The volume is measured and then the carbon dioxide 
that has been formed is determined by absorption. From these 
data the carbon monoxide and the hydrogen (which of course 
burns also) are calculated. At the above temperature methane 
is not oxidized. The speed of flow of the gases through the 
U-tube has no effect upon the accuracy of the separation. 

METHANE (CH 4 ) 

Marsh-gas Fire-damp 

Properties of Methane. Specific gravity, 0.5539; weight 
of one liter, 0.7160 gram. 

According to Bunsen, i volume of water absorbs at a tempera- 
ture /, 

0.05449 0.0011807 t + 0.000010278 t 2 ; 



PROPERTIES OF THE VARIOUS GASES 241 

hence at 20, 0.03499 volume. 

One volume of alcohol absorbs at temperature /, 

0.522586 0.0028655 / + 0.0000142 t 2 ; 
hence at 20, 0.47096 volume. 

Determination of Methane. Methane may be determined 
by explosion with oxygen or air (see p. 141), by combustion with 
copper oxide (see p. 200), by combustion in the Drehschmidt 
platinum capillary tube (see p. 154) or by combustion in the 
Dennis pipette (see p. 148). 

(i) CH 4 + 2 O 2 = CO 2 + 2 H 2 

i vol. 2 vol. I vol. liquid 

The amount of methane may be ascertained either by deter- 
mining the volume of carbon dioxide that is formed, which 
will equal the volume of the methane, or by absorbing the 
carbon dioxide without measuring it and ascertaining the to- 
tal diminution in volume, J of which will equal the volume of the 
methane. 

In the opinion of the author the method of determining meth- 
ane with the combustion pipette is superior (a) to the explo- 
sion method because it permits of the combustion of the total 
residue and avoids the possibility of error through formation 
of oxides of nitrogen; (b) to the combustion with copper oxide 
because the latter calls for high and prolonged heating of the 
combustion tube; (c) and to the combustion with the Dreh- 
schmidt capillary because this method necessitates the use of a 
comparatively large volume of an explosive gas mixture, and 
further because of the tendency of the Drehschmidt tube to 
show leakage after a short period of use. 

The combustion pipette and its level-bulb may be filled with 
water if no gases other than methane and nitrogen are present 
in the gas mixture; the methane is here determined by passing 
the gases, after combustion, into a potassium hydroxide pi- 



242 GAS ANALYSIS 

pette to completely remove the carbon dioxide and then cal- 
culating the methane from the total diminution in volume (see 
above). 

If the combustion pipette and its level-bulb are filled with 
mercury and the gases are measured over mercury, then hydro- 
gen, methane and nitrogen may be determined simultaneously 
by a single combustion by measuring the contraction after com- 
bustion and the volume of carbon dioxide that is formed. 

A measured volume of the gas mixture is transferred to the 
combustion pipette and is burned in the usual manner by the 
slow addition of a measured amount of oxygen (see p. 149). 
The residual gas is then passed back into the burette and the 
contraction in volume is measured. The gas mixture is next 
passed into the potassium hydroxide pipette to absorb the 
carbon dioxide and is then again drawn back into the burette 
and measured. 

Since one volume of methane produces, on combustion, one 
volume of carbon dioxide (see Equation i), the volume of the 
methane in the gas mixture is equal to the volume of carbon 
dioxide formed. 

Since 

(2) 2 H 2 + O 2 =2 H 2 O, 

2 vols. i vol. liquid 

the contraction due to the combustion of hydrogen is equal to 
f the volume of hydrogen in the gas mixture. The contraction 
due to the combustion of methane (see Equation i) is equal to 
twice the volume of the carbon dioxide formed. Consequently 
the total contraction in the gas volume that results when a mix- 
ture of hydrogen and methane is burned may be represented 
by the expression 

Contraction = f H 2 + 2 CO 2 
or f H 2 = Contraction 2 CO 2 

or vol. H 2 = f (Contraction 2 C02) 



PROPERTIES OF THE VARIOUS GASES 



243 



The volume of hydrogen in the gas mixture is therefore found 
by subtracting twice the volume of carbon dioxide formed in 
the combustion from the total contraction, and taking f of the 
remainder. 

The following analyses, taken from actual practice, show the 
order in which the various measurements are made, and illus- 
trate the accuracy of the determination with the combustion 
pipette. 





I 


II 


III 


IV 


V 


Gas residue taken . . 


cc. 
61 .4 
98.5 
159-9 
58.8 

101 .1 

34.3 
24.5 

Per cent 
56.4 
39-9 
3-7 


cc. 

64.50 

96.55 
161.05 

54.95 

106.10 

29.15 
25.80 

Per cent 
56.30 
40.00 
3-70 


cc. 
67.00 

98.55 
165-55 
55-30 

110.25 

28.60 
26.70 

Per cent 
56.60 
39-90 
3-50 


cc. 
64.0 
97-6 
161.6 
56.3 
105-3 

30.7 
25-6 

Per cent 
56.4 
40.0 
3-6 


cc. 

65-7 

IOO.O 

165.7 

57-6 
108.1 

3i-4 
26.2 

Per cent 
56-5 
39-9 
3-6 


Oxygen taken 


Total 
Residue after combustion .... 
Contraction 
Residue after absorbing CO2 in KOH 
pipette , _ 7 . 
Carbon dioxide found / . 


Hydrogen . 


Methane 


Nitrogen (diff ) . 





Hydrogen, methane, carbon monoxide and nitrogen may be 
determined by a single combustion if, in addition to the meas- 
urement of the total contraction and of the volume of carbon 
dioxide formed, the volume of oxygen consumed in the combus- 
tion is ascertained. 

The combustion is carried on exactly in the manner described 
above for a mixture of hydrogen, methane and nitrogen except 
that after the carbon dioxide has been absorbed and the residue 
measured, the excess of oxygen is determined by passing the gas 
residue into a pipette containing alkaline pyrogallol or sodium 
hyposulphite and subtracting this result from the total volume 
of oxygen added. The difference is the oxygen consumed in the 
combustion. Having thus ascertained the contraction resulting 
from the combustion, the volume of carbon dioxide formed, and 



244 GAS ANALYSIS 

the amount of oxygen consumed, we have all the data necessary 
for the calculation of the amounts of carbon monoxide, hydrogen, 
methane and nitrogen existing in the original mixture. 

The volume changes that result from the combustion of 
hydrogen and methane are shown in Equations i and 2 on 
pages 241 and 242. When carbon monoxide is burned, two vol- 
umes of the gas unite with one volume of oxygen to form two 
volumes of carbon dioxide. 

(3) 2 CO + 2 = 2 C0 2 . 

2 VOls. I Vol. 2 V01S. 

From these three equations the following expressions may be 
derived: 

Contraction = % CO + f H 2 + 2 CH 4 . 
Carbon dioxide formed = CO + CH 4 . 
Oxygen consumed = i CO + i H 2 + 2 CH 4 . 

From these last three equations a variety of formulas for the 
calculation of the various components of the original mixture 
may be derived. Noyes and Shepard give 

(1) H 2 = Contraction minus oxygen consumed. 

(2) CO = | (2 CO 2 + -J- H 2 minus oxygen consumed). 

(3) CH 4 = CO 2 CO. 

(4) N 2 = Original volume (H 2 + CO + CH 4 ). 
Instead of (2) and (3) we may also use 

CO = CO 2 CH 4 . 

OTT 2 Contraction CO 2 3 H2. 
CH 4 = 

3 

If no nitrogen is present in the original mixture the following 
equations of Vignon may be employed, V representing the vol- 
ume of the gas mixture taken for the combustion. 



PROPERTIES OF THE VARIOUS GASES 



245 



H 2 = V CO 2 . 

CO = i CO 2 + V f contraction. 
CH 4 = f CO 2 + f contraction V. 

The following analyses, taken from actual practice, illustrate 
the determination of carbon monoxide, hydrogen and methane 
by this method. The determination of nitrogen " by difference," 
after the removal of the absorbable and combustible constitu- 
ents, does not yield accurate results. It is distinctly preferable 
to ascertain directly the amount of nitrogen in the gas mixture 
by the method outlined on p. 317. 





I 


II 


III 


IV 




cc. 


cc. 


cc. 


cc. 


Volume of gas residue taken . 


83 45 


85.05 


83 05 


86.Q5 


Oxygen added 


97-65 


96.25 


97.90 


99-95 


Total . 


181.10 


181.30 


180.95 


186.90 


Volume after combustion 


49-30 


46.95 


49-75 


49-50 


Contraction resulting from com- 










bustion 


131 80 


134 35 


131.20 


137 40 


Volume after absorption of carbon 










dioxide . 


13-05 


10.15 


13-75 


12. OO 


Volume of carbon dioxide formed 










in the combustion .... 


36.25 


36.80 


36.00 


37 50 


Volume after absorption of excess of 










oxygen ........ 


2-53 


2.60 


2-45 


2.62 


Oxygen in excess 


10.52 


7-55 


11.30 


9-38 


Oxygen consumed in combustion 










of CO, H 2 , and CH 4 ... . 


87-13 


88.70 


86.60 


90 57 



From the above experimental results the calculated percent- 
ages of the various gases are as follows: 





I 


II 


in 


IV 


Carbon monoxide 


Per cent 
6 2 


Per cent 

6 i 


Per cent 
6 2 


Per cent 

6 o 


Hydrogen 
Methane , 
Nitrogen (difference) .... 


53 5 
37 3 
30 


53 7 
37-2 
30 


53 7 
37-2 
2.9 


53 9 
37-i 
30 



246 GAS ANALYSIS 

In a recent article x Hempel states that he has found it difficult 
to obtain complete combustion of methane with the Dennis 
combustion pipette when methane is mixed with nitrogen. He 
asseverates that when the ordinary procedure is followed, a part 
of the methane may escape combustion, and that for complete 
combustion it is necessary to maintain the spiral at red heat for 
a considerable length of time, which causes surface oxidation of 
the mercury in the pipette, and, as a consequence, too high con- 
traction. There is no doubt that this error would result if the 
spiral were subjected to prolonged heating, but experience of 
several years with the combustion pipette leads the author to 
believe that the maintenance of the spiral at red heat for sixty 
seconds after the introduction of the gas suffices in all cases for 
complete combustion of the methane, a statement that seems to 
be borne out by the analyses given on pages 243 and 245 and 
many others that might be cited. When the spiral is heated for 
so brief a time no appreciable oxidation of the mercury in the 
pipette results. 

THE HEAVY HYDROCARBONS 

As used in technical gas analysis, the term "heavy hydro- 
carbons" comprises gases of the series CnH 2 n (the olefines), 
such as ethylene, C2H 4 , propylene, C 3 H 6 , and butylene, C 4 Hs; 
of the series CnH^n _ 2, such as acetylene, C2H2; and of the series 
CnH2n_6, such as benzol (benzene), C 6 H 6 , and toluol (toluene) 
C 7 H 8 . 

The heavy hydrocarbons are the chief illuminants in coal gas 
or carburetted gas, and for this reason their determination is of 
importance when the gas is to be used directly for illuminating 
purposes . 

Absorption of Heavy Hydrocarbons. All of these gases are 
absorbed by fuming sulphuric acid of about 1.94 specific gravity 
containing about 24% free sulphur trioxide at 15. The acid 
is placed in a special absorption pipette of the form shown in 

1 Zeit.f. angew. Ghent., 36 (1912), 1841. 



PROPERTIES OF THE VARIOUS GASES 



247 



Fig. 86. The small upper absorption bulb B is about 5 cm. in 

diameter and is filled by the glass-blower with pieces of broken 

glass which serves to increase the surface of contact between the 

gas and the acid. When broken glass is used in gas pipettes 

there is danger that some gas may be trapped between the pieces 

of glass. This may usually be 

avoided by drawing up the liq- 

uid very slowly in the bulb that 

contains the broken glass. The 

fuming sulphuric acid is intro- 

duced into the pipette through 

A. When the pipette is not in 

use A and C are covered with 

small glass caps made from 

glass tubing. 

To effect the removal of the 
heavy hydrocarbons, the glass 
caps on the pipette are removed, 
and a short piece of small rubber 
tubing, such as is used on the 
other gas pipettes, is slipped 
upon C. A pinchcock is placed 
upon this rubber tube. The acid 

in the pipette is driven up in the capillary to the point marked 
H by blowing through a rubber tube that has been attached to 
the end A, and the pinchcock is closed. The pipette and gas 
burette are then connected by an empty, dry capillary tube of 
the usual form. The gas mixture is then slowly passed over into 
the pipette, and after a few seconds is slowly drawn back into 
the burette. This is repeated three times or more, the number 
of passages of the gas depending upon the per cent of the heavy 
hydrocarbons present and the strength of the acid. Throughout 
the operation the fuming sulphuric acid should never be drawn 
above the point H in the capillary of the pipette. When the gas 
is drawn back into the burette the last time, the acid in the 




JT IG 



248 GAS ANALYSIS 

pipette should be brought exactly to the point H. The pinch- 
cock at the top of the burette is now closed. The diminution 
in the gas volume may not yet be read off on the burette because 
of the presence in the gas of sulphur trioxide from the fuming 
acid in the pipette. This, together with any sulphur dioxide 
that may have been formed during the absorption, is removed 
by passing the gases into a pipette filled with potassium hy- 
droxide (see p. 225). Then gas is then drawn back into the bu- 
rette and the decrease in volume noted. 

The moisture content of the gas, after it has been brought 
into contact with the fuming sulphuric acid and the potassium 
hydroxide, will of course be less than at the beginning of the 
determination when the gas was "saturated" with water vapor. 
To avoid error from this cause in the final measurement the 
gas must in this, as in all other similar absorptions, finally be 
read over water or over mercury upon which stands a drop of 
water. 

This method of manipulation introduces slight errors in the 
results for those gases that are determined after the heavy 
hydrocarbons are removed, because the connecting capillary 
tube and the upper part of the capillary of the pipette are filled 
with air when the burette and pipette are connected. The 
volume of air in the capillaries is, however, so small 1 that the 
errors arising from this source may be disregarded in technical 
analyses. 

ETHYLENE (^H^) 

Properties of Ethylene. Specific gravity, 0.9684; weight 
of one liter, 1.2520 grams. 

One volume of water absorbs at temperature /, 

0.25629 0.00913631 t + 0.000188108 t 2 ', 
hence at 20, 0.1488 volume (Bunsen). 

1 The length of the empty capillary tube need not exceed 16 cm. which has a 
volume of only 0.16 cc. 



PROPERTIES OF THE VARIOUS GASES 249 

One volume of alcohol absorbs at t, 

3.59498 0.057716 i + 0.0006812 t 2 ; 

hence at 20, 2.7131 volumes (Carius). 

Ether absorbs about twice its volume, turpentine oil and pe- 
troleum two and a half times their volumes, and olive oil its 
own volume of ethylene. 

Determination of Ethylene by Absorption. Bromine water 
absorbs the gas rapidly and completely; l the vapor of bromine 
must be removed after the absorption by passing the gas into a 
potassium hydroxide pipette. The reagent is prepared by dilut- 
ing saturated bromine water with twice its volume of water. It 
then contains about one per cent of bromine. The liquid is 
placed in a Hempel double absorption pipette for liquid reagents 
(Fig. 36) with water in the last two bulbs. 

The usual absorbent for ethylene is fuming sulphuric acid, 
ethionic acid, C2H 6 S2O7, being formed. The determination is 
carried out in the manner described on p. 247. 

Determination of Ethylene in presence of Acetylene. 
Tucker and Moody state 2 that ethylene may be determined in 
mixture with acetylene by passing the gases through an ammoni- 
acal silver solution which removes acetylene completely but ab- 
sorbs only a relatively small amount of ethylene. The method is 
not exact but it might prove useful in an approximation of the 
percentages of ethylene and acetylene in a mixture of the two 
gases. The ammoniacal silver solution that is used in this sep- 
aration is prepared by dissolving 10 grams of silver nitrate in 
500 cc. of distilled water, adding dilute hydrochloric acid until 
the solution is barely acid to litmus paper, and then adding am- 
monium hydroxide until the solution is slightly ammoniacal. 
When acetylene is absorbed by this solution, silver acetylide, 
Ag 2 C2, is formed. 

1 Treadwell and Stokes, Berichte der deutschen chemischen Gesettschaft, 21 (1888), 
3131; Haber and Oechelhauser, ibid., 29 (1896), 2700. 

2 J. Am. Chem. Soc., 23 (1901), 671. 



250 GAS ANALYSIS 

Separation of Ethylene from Benzene. The separation 
of ethylene from benzene may, according to Haber and Oechel- 
hauser, 1 be accomplished by means of bromine water which 
removes the ethylene completely but does not appreciably 
attack the benzene if the contact between gas and reagent is not 
prolonged beyond two minutes. Some benzene vapor is, how- 
ever, mechanically carried down by the bromine vapor, and for 
this reason the method does not yield very accurate results. 

Separation of Ethylene from Butylene. Fritzsche states 2 
that ethylene may be volumetrically separated from butylene 
by means of sulphuric acid of 1.62 specific gravity which absorbs 
butylene but not ethylene. 

PROPYLENE (C 3 H 6 ) 

Specific gravity, 1.4527; weight of one liter, 1.878 grams. 

The gas may be determined by absorption with fuming sul- 
phuric acid or by combustion. Details of these methods are 
given on pages 247 and 149. 

ACETYLENE 

Properties of Acetylene. Specific gravity, 0.8988; weight 
of one liter, 1.1620 grams. 

Acetylene is quite soluble in a number of liquids, as is shown 
in the following table: 3 

at 12 and 755 mm. 

i vol. saturated salt solution dissolves o . 23 vol. acetylene 
i " water " 1.18 " " 

at 1 8 and 760 mm. 

i vol. carbon disulphide dissolves i . o vol. acetylene 
i " oil of turpentine " 2.0" " 

i " carbon tetrachloride 2.0 " " 

1 /./. Gasbdeuchtung, 39 (1896), 799; 43 (1900), 347. 

2 Z.f. angew. Chem., 1896, 456. 

3 Vogel, Handbuchfiir Acetylen, p. 152. 



PROPERTIES OF THE VARIOUS GASES 251 

at 18 and 760 mm. 

vol. amyl alcohol dissolved 3 . 5 vol. acetylene 

" styrol 3-5 " 

" chloroform 4.0 " 

" benzene 4.0 " 

" absolute alcohol " 6.0 " 

acetic acid 6.0 " 

" acetone 25 " 

at 15 and 12 atm. 
i " acetone " 300 vol. acetylene 

at 80 and 760 mm. 
i " acetone " 2000 vol. acetylene 

It is slowly absorbed by concentrated sulphuric acid, acetyl 
sulphonic acid, C 2 H 4 SO 4 , being formed. An ammoniacal solu- 
tion of cuprous chloride absorbs the gas rapidly and there is 
formed a brown to violet-red precipitate of copper acetylide, 
Cu 2 C 2 , which explodes when heated or struck. Acetylene 
produces in an ammoniacal silver solution 1 a white precipitate, 
Ag 2 C 2 , which is even more explosive than the copper acetylide. 
If the gas is led into ammoniacal solutions of aurous thiosulphate 
or potassium mercuric iodide, exceptionally explosive com- 
pounds are formed. 

All of the ammoniacal solutions of metals that have been 
mentioned may be used as absorbents for acetylene, 

Determination of Acetylene. Although acetylene may be 
determined by combustion with oxygen, this method cannot 
usually be employed because the gas occurs in mixtures with 
other combustible gases. One volume of acetylene yields on 
combustion 2 volumes of carbon dioxide. When 2 volumes of 
acetylene are burned there is a contraction of 3 volumes. 

2 C 2 H 2 + 5 O 2 = 4 CO 2 + 2 H 2 O. 
2 vols. 5 vols. 4 vols. liquid. 

1 The method of preparing this solution is described under Ethylene, p. 249. 



252 GAS ANALYSIS 

It is best determined by leading it through an ammoniacal 
cuprous chloride solution, a reddish brown precipitate being 
thrown down. The precipitate is filtered off, and is washed with 
water containing ammonia until the wash-water passes through 
colorless. The moist copper acetylide may be collected in a 
Gooch crucible and dried over calcium chloride at 100 in a cur- 
rent of carbon dioxide : and weighed as Cu 2 C 2 . Dry copper 
acetylide may, however, explode at a temperature as low as 
60. 

The acetylene may be determined, without danger of explo- 
sion, by taking advantage of the fact that the moist precipitate 
contains carbon and copper 2 in the atomic proportion of 1:1, 
and determining the copper in the moist compound. This 
is done by pouring hydrochloric acid upon the precipitate which 
is thereby decomposed with evolution of acetylene. As it is 
difficult to completely decompose the copper acetylide, the end 
of the reaction is not waited for, but the rest of the precipitate, 
without being washed, is dried on the filter and ignited. The 
copper oxide is dissolved in a few drops of nitric acid, and this 
solution is added to the hydrochloric acid filtrate first obtained. 
The copper in the solution may then be determined electrolyti- 
cally, or it may be precipitated from hot solution with sodium 
hydroxide, filtered off, washed, ignited and weighed as cupric 
oxide. 

Acetylene may be determined volumetrically in the Hempel 
apparatus by absorbing it with fuming sulphuric acid contained 
in the pipette shown in Fig. 86. It is necessary to pass the gas 
repeatedly into the pipette until no further diminution in vol- 
ume is noted upon measuring the residual gas in the burette. 
Before making the final measurement, the gas must, of course, 
be passed into the potassium hydroxide pipette to remove 
the sulphur trioxide. Traces of acetylene may still remain 
in the gas mixture after this treatment with fuming sul- 

1 Scheiber, Z. analyt. Chem., 48 (1909), 537. 

2 Scheiber, Ber. d. deutsch. Chem., Ges. 41 (1908), 3816. 



PROPERTIES OF THE VARIOUS GASES 253 

phuric acid, and these may be removed by passing the gas into 
a pipette containing an ammoniacal cuprous chloride solution. 
If oxygen is present with the acetylene, it is removed, after the 
treatment of a gas mixture with fuming sulphuric acid, by ab- 
sorption with alkaline pyrogallol. Phosphorus cannot be used 
for the absorption of oxygen in the presence of even very small 
amounts of acetylene because the gas inhibits the union between 
oxygen and phosphorus to such an extent as to render it impos- 
sible to obtain even approximately correct results for oxygen with 
this reagent. 

BENZENE (C 6 H 6 ) 

Specific gravity at 15, 0.885. Melting-point, about 6. 
Boiling-point, 80.3. 

Determination of Benzene. Benzene is rapidly absorbed 
by fuming sulphuric acid and this reagent may be employed for 
the determination of the gas if no other heavy hydrocarbons 
are present. This, however, is rarely the case, and the impor- 
tance of benzene as an illuminant renders very desirable the 
perfection of a method for the accurate volumetric separation 
and determination of benzene vapor in the presence of other of 
the heavy hydrocarbons. 

Absorption of Benzene by Alcohol. In 1891 Hempel and 
Dennis 1 proposed a method for the removal of the benzene 
vapor that was based on the ready absorption of that substance 
by absolute alcohol. They used a mercury pipette (Fig. 50) 
that contained above the mercury i cc. of absolute alcohol 
that was first saturated with the illuminating gas under exami- 
nation. After the removal of the benzene the residual alcohol 
vapor was absorbed by passing the gas residue into a mercury 
pipette containing i cc. of water. 

Further examination 2 of this method demonstrated, however, 
that the removal of benzene vapor by alcohol is not complete 

1 Berichte der deutschen chemischen Gesellschaft, 24 (1891), 1162. 

2 Dennis and O'Neill, Jour. Am. Chem. Soc., 25 (1903), 503. 



2$4 GAS ANALYSIS 

and that furthermore the solubility of various gases in alcohol l 
is so appreciable that errors arising from this cause cannot 
be entirely eliminated by saturation of the alcohol with these 
gases. 

Absorption of Benzene by Paraffin Oil. The removal of 
benzene by cooled paraffin oil was proposed by Muller. 2 The gas 
mixture is first dried by passing it through apparatus containing 
calcium chloride and is then slowly passed through an absorption 
apparatus containing liquid paraffin of 0.88 to 0.89 specific grav- 
ity and of a boiling-point of about 360. The absorption ap- 
paratus is weighed before the experiment, is cooled during the 
experiment with a freezing mixture of ice and salt, and after 
the absorption is brought to room temperature and again 
weighed. The amount of gas that is passed through the ab- 
sorbent is measured by a gas meter placed after the absorption 
apparatus. 

Determination of Benzene as Dinitrobenzene. Harbeck 
and Lunge 3 devised a method for the determination of benzene 
that is based upon the fact that benzene, when present in a 
gas mixture in relatively small amount, is quantitatively con- 
verted into dinitrobenzene when the gases are passed through a 
suitable absorption apparatus containing a mixture of equal 
weights of concentrated sulphuric acid and fuming nitric acid. 
The dinitrobenzene, which is difficultly soluble in water but 
easily soluble in ether, is extracted with ether and, after evapora- 
tion of the solvent, is weighed. From this weight the amount 
of benzene in the gas is calculated. The method is quite accu- 
rate, but unfortunately it is so time-consuming as to preclude 
its use in routine analysis. 

Pfeiffer determines 4 the dinitrobenzene obtained by the Har- 
beck and Lunge method by a volumetric procedure based upon 

1 See Lunge, Chemisch-technische Untersuchungsmethoden, 2, 585. 

2 /./. Gasbeleuchtung, 41 (1898), 433. 

3 Z.f. anorg. Chem., 1 6 (1808), 41; also Chemisch-technische Untersuchungsmethoden, 
2, 592. 

4 Chemiker-Zeitung, 28 (1904), 884. 



PROPERTIES OF THE VARIOUS GASES 255 

the reaction first mentioned by Limpricht 1 in which the dinitro- 
benzene is reduced to diamidobenzene by stannous chloride and 
the excess of the reducing agent is determined by titration with 
an iodine solution of known strength. The reactions involved 
are 

C 6 H 4 (NO 2 ) 2 + 6 SnCl 2 + 12 HC1 = 

C 6 H 4 (NH 2 ) 2 + 6 SnCl 4 + 4 H 2 O, 
SnCl 2 + 2 I + 2 HC1 = SnQ 4 + 2 HI. 

Separation of Benzene from Ethylene. In the method of 
Haber and Oechelhauser 2 the total amount of the heavy hydro- 
carbons is determined by means of fuming sulphuric acid and 
the ethylene in another sample is determined by absorption in 
bromine water of known strength and titration of the residual 
free bromine with sodium thiosulphate. Assuming that only 
benzene and ethylene are present the amount of benzene is 
equal to the difference between these two results. 

The method gives fairly accurate results, but it is open to the 
objection that, for benzene, it is indirect and that a determina- 
tion takes considerable time. 

Absorption of Benzene with Nickel Solution. Dennis and 
O'Neill 3 developed a gas volumetric method for the determina- 
tion of benzene that is based upon the reaction that takes place 
when nickel cyanide, ammonia and benzene are brought to- 
gether, the compound Ni(CN) 2 NH 3 'C 6 H 6 being formed. 4 The 
absorbent for benzene was first prepared by dissolving nickel 
nitrate in water and pouring this solution into ammonium hy- 
droxide. The resulting solution had a slight odor of ammonia. 
The reagent was placed in a Hempel simple absorption pipette, 
the gas mixture was run into the pipette and the gas shaken with 
the reagent for three minutes. It was then drawn back into the 

1 Ber. d. deutsch. chem. Ges., u (1878), 35. 

2 Jour. f. Gasbeleuchtung, 39 (1896), 799; 43 (1900), 347. 

3 J. Am. Chem. Soc., 25 (1903), 503. 

4 Hofmann and Kiispert, Z. /. anorg. Chem., 15 (1897), 204. 



256 GAS ANALYSIS 

burette, passed into a pipette containing mercury and 5 cc. of a 
5% solution of sulphuric acid to remove ammonia, after which it 
was drawn back and finally measured. The results obtained 
with this method by different analysts were, however, quite dis- 
cordant. Some chemists found the method to be very accurate 
while others reported it to be far from satisfactory. A careful 
examination of the statements from different analysts rendered 
it probable that those samples of illuminating gas with which 
the method gave good results contain the cyanogen compounds 
necessary to the formation of the product described by Hofmann 
and Kiispert, and that the poor results on other samples of 
illuminating gas might be due to the absence of cyanogen com- 
pounds in the gas. Consequently the solution of ammonia 
nickel nitrate was replaced l by a solution of ammonia nickel 
cyanide. This reagent was found to rapidly and quantita- 
tively absorb benzene from mixtures of benzene vapor with air 
as well as from samples of illuminating gas, and it was further 
demonstrated that ethylene was not taken up by the solution. 
The reagent is prepared as follows : 

To 50 grams of nickel sulphate (NiSO^y H^O), dissolved in 
75 cc. of water, is added 25 grams of potassium cyanide dissolved 
in 40 cc. of water. After the addition of 125 cc. of ammonium 
hydroxide (Sp. Gr. 0.9) the mixture is shaken until the nickel 
cyanide has completely dissolved. It is then cooled to o C. and 
allowed to stand at that temperature for twenty minutes. The 
clear liquid is decanted from the crystals of potassium sulphate 
that have separated, and is treated with a solution prepared by 
dissolving 18 grams of crystallized citric acid in 10 cc. of water. 
After the mixture has stood again at o for ten minutes, the 
greenish blue supernatant solution is decanted and is introduced 
into a gas pipette. Two drops of liquid benzene are now added 
to the reagent and the pipette is shaken until the benzene has 
combined with the reagent, which is evidenced by the appear- 
ance of a fine, granular, white precipitate in the pipette. This is 

1 Dennis and McCarthy, Jour. Am. Chem. Soc., 30 (1908), 233. 



PROPERTIES OF THE VARIOUS GASES 257 

effected in two or three minutes. This addition of benzene to 
the reagent is made because it has been found that a freshly 
prepared solution of the ammonia nickel cyanide does not 
actively remove benzene vapor until some of the compound be- 
tween benzene and the reagent has been formed. 

The reagent is placed in a Hempel double gas pipette for 
solid reagents (Fig. 37) the large bulb of the pipette being 
filled with broken glass. The absorbent is brought into the first 
two bulbs, and water is introduced into the third and fourth 
bulbs. The analytical absorbing power of the reagent is 5 ; con- 
sequently 100 cc. of the reagent in the pipette may be used in 
analytical work for the absorption of 500 cc. of benzene vapor. 

In determining benzene by this method a gas sample is 
measured off in a gas burette which is then connected by means 
of the usual capillary tube with the pipette containing the am- 
monia nickel cyanide solution. The gas mixture is repeatedly 
passed over into the pipette and drawn back into the burette 
during a period of about three minutes, which will suffice for the 
removal of the benzene in amounts up to about eight per cent. 
The gas is finally drawn into the burette which is then joined to 
a double pipette of the form shown in Fig. 37. The bulb A is 
filled with glass tubes and A and B are then charged with a 
five per cent solution of sulphuric acid. Bulbs C and D are 
filled with sufficient water to protect the reagent from the air. 
The gas residue is now passed back and forth about two minutes 
to remove the ammonia that enters the. gas mixture from the 
reagent. If mercury is used as the confining liquid in the burette 
the small amount of water that usually covers its surface will 
absorb ammonia from the reagent. This may rapidly be re- 
moved by drawing into the burette from the pipette sufficient 
dilute sulphuric acid to completely neutralize the ammonium 
hydroxide thus formed and then driving the acid back into the 
burette. 

Both reagents must of course first be shaken with samples of 
the gas mixture under analysis in order to saturate the absorb- 



258 GAS ANALYSIS 

ents with those constituents of the mixture which they do not 
absorb. 

The majority of those who have used this method in technical 
practice have found that it gives uniform and accurate results. 1 

On the other hand, some report that even in its modified form 
the method is not satisfactory. In the greater number of such 
cases, correspondence with the analyst has developed either that 
the reagent was not properly prepared or that the absorption 
apparatus was of an inefficient type. But little weight can be 
attached to the criticism of the method by Harding and Taylor 2 
because of the unconvincing character of the experimental 
work of those authors. They compared the results by the 
ammonia nickel cyanide method with those obtained by another 
method of dubious accuracy, 3 using a gas mixture of unknown 
benzene content, and they assume that differences in the results 
are due to the inaccuracy of the first named method. They 
further found that prolonged contact between the gas mixture 
and the ammonia nickel cyanide and dilute sulphuric acid caused 
a slow but steady diminution of the gas volume and they as- 
cribed this to the absorption by the reagent of hydrocarbons 
other than benzene. 

To test the correctness of this assumption and to ascertain 
whether, as Harding and Taylor maintain, there is slow but 
continuous absorption of gas upon repeated passage of the resi- 
due into ammonia nickel cyanide and 5 per cent sulphuric 
acid, the following experiments were carried out in the author's 
laboratory by Mr. E. L. Davies. Mr. Davies placed the solu- 
tion of ammonia nickel cyanide and of 5 per cent sulphuric 
acid in the double Hempel pipettes above mentioned and passed 
into these pipettes samples of the city gas of Ithaca, which is a 
mixture of coal gas and carburetted water gas. Carbon dioxide 

1 See, for example, Pfeiffer, Z.f. angew. Chem., 20 (1907), 22; Stavorinus, Het Gas, 
1905, p. 554; /./. Gasbeleuchtung, 49 (1906), 272. 

2 Jour. Ind. and Eng. Chem., 2 (1910), 345. 

3 See Haber, Jour.f. Gasbeleuchtung, 43 (1900), 511. 



PROPERTIES OF THE VARIOUS GASES 



259 



was of course first removed from the gas by means of potassium 
hydroxide. He obtained the results that are tabulated below. 





May 27, 

IQI2 


May 28, 

IQI2 


May 29, 

IQI2 


Volume of residue after removal COz . 
Volume after 3 minutes treatment with 
nickel solution and 7 minutes treatment 
with 5% H2SO4 


96.8 cc. 

Q2 6 CC. 


97.0 cc. 

04. . 2 CC. 


96.8 cc. 

04. CC. 


Volume after first repetition with these two 
reagents . . 
Volume after 26. repetition 
" id 


93 . 6 cc. 
93.6cc. 

01 ^ CC. 


94.2 cc. 
94.2 cc. 

04 . 2 CC. 


94 cc. 
94 cc. 
94 CC. 


" " 4th " . . . 


Ql . ^ CC. 


94 . 2 CC. 


94 CC. 


" 5th " 
" 6th " 




94 . 2 cc. 
94 . 2 cc. 


94 cc. 
94.1 cc. 


Total duration of contact with nickel solu- 
tion 


1 8 min. 


24 min. 


18 min. 


Total duration of contact with 5% H2SO4 
Total duration of contact with both re- 
agents 


42 min. 
60 min. 


56 min. 
80 min. 


42 min. 
60 min. 



The above analyses appear to demonstrate conclusively that 
the solutions of ammonia nickel cyanide and 5 per cent sul- 
phuric acid do not gradually absorb constituents of the gas 
mixture other than benzene. 

The results of the experiments with ethylene described by 
Harding and Taylor are directly contradictory to those cited by 
Dennis and McCarthy and are probably incorrect both because 
of impurities in the ethylene that was used and because of solu- 
tion and escape of the gas through the single outer bulb. That 
they find that a gas mixture containing ethylene diminishes in 
volume when shaken with ammonia nickel cyanide for even so 
short a time as one or two minutes is but natural, because in this 
as in all other cases in gas analysis a liquid reagent will dissolve 
somewhat of a gas and must be saturated with the gas before the 
analysis is made. 1 That acetylene dissolves both in the reagent 
1 See Dennis and McCarthy, loc. cit., p. 238. 



260 GAS ANALYSIS 

and in the 5% sulphuric acid is not at all surprising because that 
gas is quite soluble even in distilled water. The point is quite 
beside the question in the present case because acetylene does 
not occur as a constituent of ordinary illuminating gas. 

Stavorinus J subjected the method to a careful experimental 
examination and found that the reagent did not absorb air, 
hydrogen, carbon monoxide, methane, pentane, ethylene, or 
propylene. He continues, "Acetylene on the other hand was 
absorbed, which was to be expected, but since this gas is present 
in illuminating gas in scarcely detectable traces it may be dis- 
regarded. . . . Gases carburetted with benzene gave excel- 
lently agreeing results, and the method can furthermore be 
commended because of its simplicity of manipulation, and its 
speed." 

NAPHTHALENE (CioHg) 

Melting-point, 79; boiling-point, 218. 

Naphthalene is a white crystalline substance that is solid at 
ordinary temperatures. It is, however, quite volatile and for 
that reason its vapor is frequently present in carburetted gas. 

Determination of Naphthalene. For the determination of 
naphthalene in gas mixtures the method original with Colman 
and Smith, 2 and modified and improved by Gair, 3 Rutten, 4 Col- 
man, 5 Jorissen and Rutten, 6 and Albrecht and Miiller 7 is almost 
exclusively employed. It is based upon the fact, first noted by 
Fritzche, 8 that naphthalene unites with picric acid to form a 
crystalline compound of the formula CioHs'CeHsNaOr, which is 
but slightly soluble in a saturated or nearly saturated solution 

1 Loc. cit. 

2 Jour. Soc. Chem. Ind., 19 (1900), 128. 

3 Jour. Soc. Chem. Ind., 24 (1905), 1279. 

4 Eel Gas, 1908, Nos. 9 and 12. 

5 Jour. Soc. Chem. Ind., 28 (1909), 1179. 

6 Jour. f. Gasbeleuchtung, 53 (1910), 269. 
7 Jour.f.Gasbeleuchtung, 54 (1911), 592. 
8 Jour, prakt. Chem., 73 (1858), 282. 



PROPERTIES OF THE VARIOUS GASES 261 

of picric acid. After absorption of the naphthalene, the excess 

N 

of free picric acid is titrated with potassium hydroxide. 

The determination may be carried out as follows: 

The gas mixture, which must be free from tar, cyanogen, 
hydrogen sulphide and ammonia, 1 is passed through two gas 
washing bottles containing a saturated solution of picric acid 
together with some undissolved picric acid. This absorbing 
solution is prepared by weighing off exactly 2.5 grams of picric 
acid, dividing this amount of the acid into two nearly equal 
portions, placing one portion in a gas washing bottle of 100 cc. 
capacity, adding 25 cc. of water and then shaking the bottle 
vigorously until a saturated solution of picric acid is formed. 
The other portion of the solid picric acid is then placed in a 
second gas washing bottle and treated in similar manner. The 
two bottles are then connected to each other glass to glass by 
rubber tubing, and the gas mixture -is led through the absorbent 
at a rate of from 40 to 50 liters per hour. The total volume of 
gas passed through the picric acid is measured by a gas meter 
placed after the wash bottles and it should be such as will 
contain not less than 0.05 gram and not more than 0.20 gram of 
naphthalene. 2 

The contents of the two wash bottles including the undis- 
solved picric acid is carefully transferred to a 250 cc. measuring 
flask, the wash bottles being rinsed with water. The stopper of 
the flask is inserted, and the flask is then heated on a water bath 
for half an hour, with frequent shaking, to from 40 to 50. 
This will cause the complete solution of all of the picric acid. 

In the meantime 2.5 grams of picric acid is weighed out into 
another 250 cc. measuring flask, is dissolved in water and is 
diluted to the mark; 200 cc. of this solution is then titrated 

with potassium hydroxide, lacmoid being used as indicator. 

1 See analysis of illuminating gas, p. 306. 

2 Albrecht and Miiller, loc. cit. 



262 GAS ANALYSIS 

The measuring flask that contains the picric acid by which the 
naphthalene has been absorbed is allowed to cool to the temper- 
ature of the room and is then filled to the mark with water, the 
contents thoroughly shaken, and 200 cc. of the solution is filtered 
off through a dry filter. This filtrate is then also titrated with 

potassium hydroxide. The difference in the number of cubic 

centimeters of potassium hydroxide used in the two titrations 
multiplied by f- X 0.0128 gives the grams of naphthalene ab- 
sorbed by the picric acid in the two wash bottles. This amount 
is then calculated to grams of naphthalene per cubic meter of gas. 

CYANOGEN (C 2 N 2 ) 

Properties of Cyanogen. Specific gravity, 1.7993; weight 
of one liter, 2.3261 grams. 

One volume of water dissolves at 20, 4.5 volumes of cyanogen; 
i volume of alcohol, 20 volumes of cyanogen. 

Burned with twice its volume of oxygen it forms 2 volumes of 
carbon dioxide and i volume of nitrogen. 

Detection of Cyanogen. Free cyanogen, or dicyanogen, 
may be detected according to Kunz-Krause 1 by the Schonbein- 
Pagenstecher reaction. For carrying out this test, strips of 
filter paper are first dipped into a dilute aqueous solution of 
copper sulphate (1:1000), and are then impregnated with a 
3 per cent tincture of gum guaiac. The paper thus prepared 
turns blue when acted upon by dicyanogen or hydrocyanic acid, 
but this blue color is also caused by certain oxidizing agents 
such as ozone and nitric acid. 

The reaction is somewhat sharper when the gas mixture, 
instead of being brought in contact with the paper above 
described, is passed through a wash bottle containing an alcoholic 
copper sulphate gum guaiac solution. 

The reaction has lately been increased in delicacy by E. 
Schaer, who uses guaiaconic acid in place of the gum guaiac. 

1 Zeitschr. angew. Chem., 26 (1901), 652. 



PROPERTIES OF THE VARIOUS GASES 263 

The reagent should always be freshly prepared, and this is done 
by adding to 10 cc. of a dilute aqueous copper sulphate solution 
15 cc. of alcohol in which a little guaiaconic acid has previously 
been dissolved. 

Brimnich states 1 that the delicacy of the Schonbein-Pagen- 
stecher test for hydrogen cyanide may be greatly enhanced by 
moistening the paper with formalin instead of with water before 
exposing the paper to the gas mixture under examination. The 
color that here results if hydrogen cyanide is present is deep 
blue, whereas, if the paper is moistened with water, it is a light 
blue. 

Another delicate reaction for dicyanogen is given by Kunz- 
Krause in the article above cited, this test depending upon the 
formation of isopurpuric acid or picrocyaminic acid, C 8 H 5 N 5 O6, 
from picric acid. 2 cc. of a cold saturated aqueous solution of 
picric acid (i: 86) is mixed with 18 cc. of alcohol and 5 cc. of a 
15 per cent aqueous solution of potassium hydroxide. When 
brought into contact with this solution pure cyanogen yields a 
deep purple-red color, which later turns to brown. On long 
standing the potassium salt of isopurpuric acid separates in the 
form of an oil of purple-red color. This reagent also must always 
be freshly prepared. 

Potassium hydroxide absorbs cyanogen, potassium cyanide 
and potassium cyanate being formed. 

C 2 N 2 + 2 KOH = KCN + KCNO + H 2 0. 

Determination of Cyanogen. Cyanogen may be determined 
by the method of Nauss. 2 100 liters of the gas mixture is passed 
at a rate of from 50 to 100 liters per hour through two absorp- 
tion bottles in each of which is placed 20 cc. of a solution of 
ferrous sulphate (1:10) and 20 cc. of a solution of potassium 
hydroxide (1:3). After the passage of the gas, the contents of 
the absorption bottles is carefully rinsed into a 500 cc. flask, 

1 Chemical News, 87 (1903), 173. 

2 J. Gasbeleitchtung, 43 (1900), 696. 



264 GAS ANALYSIS 

some potassium hydroxide in solution is added and then ferrous 
sulphate (1:10). If hydrogen sulphide is present, the solution 
of ferrous sulphate should be added until no further precipita- 
tion of black ferrous sulphide results. It is advisable to add 
also about one gram of lead carbonate to ensure the complete 
removal of hydrogen sulphide. The contents of the flask is then 
heated for some minutes and allowed to cool. The flask is filled 
to the mark, and 5 cc. more of water is added to compensate for 
the volume of the precipitate. After being vigorously shaken, 
the liquid is filtered off through a dry paper; 50 cc. of the 
filtrate is poured into an excess (20 to 30 cc.) of a hot solution of 
ferric alum that contains 200 grams of ferric alum to the liter. 
The solution is warmed for a short time on a water bath and 
Prussian blue is then precipitated by the addition of dilute 
sulphuric acid. The precipitate is collected on a folded filter in 
a hot-water funnel, and is washed with hot water until sulphuric 
acid has been completely removed. The precipitate with the 
filter is then at once placed in a flask, some water is added, and 
the liquid is heated to boiling, the contents of the flask being 
frequently shaken to loosen the precipitate from the paper. The 
amount of the Prussian blue is then directly determined by 
titration with a -^N solution of sodium hydroxide. 

Fe 4 (Fe(CN) 6 ) 3 + 12 NaOH = 4 Fe(OH) 3 + 3 Na 4 Fe(CN) 6 . 

The solution of sodium hydroxide is added, a little at a time, 
until all of the Prussian blue is decomposed. The contents of 
the flask is kept hot during the addition of the sodium hydroxide 
for the purpose of hastening the reaction. The excess of sodium 
hydroxide is then ascertained by titrating back with -^N acid. 
The liquid must be continuously heated and frequently shaken 
during this last titration, for even in the presence of an excess of 
sodium hydroxide there is some re-formation of Prussian blue 
which causes a green coloration of the liquid. When the color 
changes to a light greenish yellow, the end point has been reached. 

i cc. -jpj-N sodium hydroxide = 0.0007794 gram cyanogen. 



PROPERTIES OF THE VARIOUS GASES 265 

Nauss found from 6 to 15 grams of cyanogen in 100 cubic 
meters of Karlsruhe gas after the last purifier. 

Samtleben, using the analytical method of Nauss, found * in 
coal gas of Bernburg from 155 to 301 grams of hydrogen cyanide 
in 100 cubic meters before the purifiers, and from 8.8 to 21.3 
grams per 100 cubic meters after the purifiers. 

Detection and Determination of Cyanogen in presence of 
Hydrogen Cyanide. Wallis 2 observed that when hydrogen 
cyanide is passed into an acidified solution of silver nitrate it re- 
acts quantitatively with the silver nitrate to precipitate silver 
cyanide. He also states that cyanogen does not react with an 
acidified solution of silver nitrate, and that any cyanogen that 
dissolves as such in the reagent may be removed practically com- 
pletely by passing a current of air through the solution. Upon 
this difference of behavior of cyanogen and hydrogen cyanide 
toward silver nitrate, Wallis bases a method for the detection 
of cyanogen and of hydrogen cyanide when these gases are 
present together in a gas mixture, but he carried the work no 
further than to show the applicability of this method to the 
qualitative examination of a few special gas mixtures. 

Quite recently Rhodes has made a careful study of the re- 
action noted by Wallis and has developed a method 3 that 
permits both of the detection and of the accurate determina- 
tion of cyanogen in the presence of hydrogen cyanide. For 
the detection of cyanogen in the presence of hydrogen cyanide 
he proceeds as follows 

Test tubes 15 cm. long and provided with side arms are used 
for the absorption of the gases. In one such tube is placed 10 cc. 
of a 10 per cent solution of silver nitrate to which one drop of 
dilute (6 N) nitric acid has been added. In the second tube is 
placed 10 cc. of a 2 N solution of potassium hydroxide. The two 
absorption tubes are connected in series and the gas mixture is 

1 /. Gasbeleuchtung, 49 (1906), 205. 

2 Annalen (Liebig) 345 (1906), 353. 

3 J. Ind. and Eng. Chem., 4 (1912), 652. 



266 GAS ANALYSIS 

passed through them. The duration of the passage of the gas 
depends upon the amount of hydrogen cyanide in the gas mix- 
ture. Since the first tube is intended to hold back the hydrogen 
cyanide, the passage of the gas must of course be stopped before 
all of the silver nitrate in this tube is converted into silver cy- 
anide. After the gas mixture has been passed through the ab- 
sorption tubes for a sufficient length of time, it is replaced by a 
current of air which is continued for about ten minutes. The 
second absorption tube, which contains the solution of potas- 
sium hydroxide, is then disconnected and 5 cc. of a solution of 
ferrous sulphate and one drop of a solution of ferric chloride 
are added to the contents of the tube. After about fifteen min- 
utes there is added dilute sulphuric acid in amount sufficient to 
dissolve the ferrous and ferric hydroxides. The appearance of 
a blue precipitate or of a distinct green color in the solution after 
acidification proves the presence of cyanogen in the original 
gas mixture. The delicacy of this reaction for cyanogen is 
shown by the results in the following table : 

VOLUME OF CYANOGEN COLOR DEVELOPED 

10. cc. Blue precipitate 

5 . cc. Blue precipitate 

i . cc. Blue precipitate 

0.4 cc. Green color 

0.3 cc. Faint green color 

o . 2 cc. Very faint green color 

From the above data it appears that as small an amount as 
0.3 cc. of cyanogen may be detected in this manner. That the 
presence of hydrogen cyanide in the gas does not interfere with 
the delicacy of this method was demonstrated by passing through 
the absorbents a mixture of 0.4 cc. of cyanogen and 10 cc. of 
hydrogen cyanide and obtaining a distinct reaction for cyanogen 
under these conditions. 

Since potassium cyanide is hydrolyzed to a considerable degree 
in aqueous solution with the formation of hydrocyanic acid, 



PROPERTIES OF THE VARIOUS GASES 267 

it was thought possible that the passage of a large volume of 
air through the apparatus might carry with it some of the hydro- 
gen cyanide, and thus decrease the delicacy of the test. It was 
found, however, that this was not the case, 0.4 cc. of cyanogen 
still yielding a distinct reaction when 20 liters of air was passed 
through the apparatus subsequent to the introduction of the 
cyanogen. 

A small amount of carbon dioxide in the gas mixture under 
examination does not interfere with the test for cyanogen. But 
if an amount of gas containing carbon dioxide sufficient to con- 
vert all of the potassium hydroxide into potassium carbonate 
is passed through the reagent, the reaction for cyanogen is then 
not obtained. 

The presence of hydrogen cyanide in the original gas mixture 
is detected by collecting on a filter any precipitate that may 
have formed in the solution of silver nitrate in the first absorp- 
tion tube, washing the precipitate with very dilute nitric acid, 
drying it, transferring it to a small sublimation tube, and 
warming it with a small amount, five milligrams or less, of 
iodine. The formation of a sublimate of cyanogen iodide on 
the side of the tube proves the presence of silver cyanide in 
the precipitate and consequently of hydrogen cyanide in the 
original gas mixture; o.i mg. of silver cyanide, equivalent 
to 0.02 mg. of hydrogen cyanide, may be detected in this 
manner. 

To determine cyanogen and hydrogen cyanide in the presence 
of each other the gas mixture is passed through a series of four 
absorption test tubes. Each of the first two of these tubes con- 
tains 5 cc. of a standardized (approximately ) solution of 

silver nitrate and one drop of dilute nitric acid. In the third 
absorption tube is placed 10 cc. of an approximately 2 N solu- 
tion of potassium hydroxide that is free from chloride, and the 
last tube contains 5 cc. of this solution. The gas mixture under 
examination is slowly passed through this absorption apparatus 



268 GAS ANALYSIS 

or is carried through by a slow current of air. The first two 
absorption tubes are then disconnected and the solution of 
silver nitrate that they contain is transferred to a beaker and is 
filtered. The precipitate and filter paper are washed with very 
dilute nitric acid until free from soluble silver salts. The filtrate 
and wash water are then combined and are titrated with a stand- 
ardized solution of ammonium sulphocyanate with ammonium 
ferric alum as indicator, and the amount of hydrogen cyanide 
that was present in the original gas mixture is calculated from 
the volume of ammonium sulphocyanate used. 

The contents of the third and fourth absorption tubes is 
transferred to a beaker and a known volume of a standardized 
solution of silver nitrate is added. The silver nitrate must be 
in excess of the amount required to precipitate all of the potas- 
sium cyanide in the solution as silver cyanide. The solution 
and the suspended precipitate, are then thoroughly stirred, and 
dilute nitric acid is next added until the precipitated silver oxide 
redissolves and the solution becomes slightly acid. The pre- 
cipitate of silver cyanide is now filtered off, the precipitate and 
filter paper are washed with very dilute nitric acid until all 
soluble silver salts are removed, and the filtrate and wash water 
are combined and are titrated with a standardized solution of 
ammonium sulphocyanate with ammonium ferric alum as in- 
dicator. The cyanogen present in the original gas mixture is 
then calculated, the reactions involved in the calculation 
being: 

(CN) 2 + 2 KOH = KCN + KCNO + H 2 O 
KCN + AgNO 3 = AgCN + KNO 3 
AgNO 3 + KCNS = AgCNS + KNO 3 

Analyses made by this method of mixtures of known amounts 
of cyanogen and hydrogen cyanide showed that the procedure 
gives very satisfactory results. 



PROPERTIES OF THE VARIOUS GASES 269 

HYDROGEN CYANIDE (HCN) 

Properties of Hydrogen Cyanide. Specific gravity, 0.9359; 
weight of one liter, 1.2096 grams. 

The gas is easily soluble in water and in alcohol, and is ab- 
sorbed by potassium hydroxide with the formation of potassium 
cyanide. 

Strong acids, especially hydrochloric acid and sulphuric acid, 
decompose hydrocyanic acid with formation of formic acid and 
ammonia. 

Detection of Hydrogen Cyanide. Hydrogen cyanide may 
be detected by absorbing the gas in a solution of potassium hy- 
droxide, and then adding ferrous sulphate and one drop of fer- 
ric chloride to the solution of potassium cyanide. (If the solu- 
tion that is being tested is not alkaline, potassium hydroxide 
should be added at this point.) The solution is then gently 
warmed and is acidified with hydrochloric acid. A dark blue 
precipitate of Prussian blue proves the presence of potassium 
cyanide in the absorbent. Since cyanogen is absorbed by potas- 
sium hydroxide with the formation of potassium cyanide, that 
gas will also give this reaction. 

Another test for hydrocyanic acid is to add ammonium sul- 
phide until the solution takes on a yellow color, then ammonia, 
or, better, a drop of sodium hydroxide, and to heat the solu- 
tion until the excess of ammonium sulphide has been driven off, 
and the solution is again colorless. In this way there is formed 
either ammonium or sodium sulphocyanate, which, after acidi- 
fying, gives the characteristic blood-red color with ferric chloride. 

Hydrogen cyanide may also be detected by the methods pro- 
posed by Kunz-Krause and by Schaer which have already been 
described under Cyanogen. 

Determination of Hydrogen Cyanide. For the determina- 
tion of hydrogen cyanide in a gas mixture the method of L. W. 
Andrews 1 may be used. The gas is absorbed in potassium hy- 

1 American Chemical Journal, 30 (1903), 187. 



270 GAS ANALYSIS 

dioxide and if the resulting solution contains more than about 
one per cent of hydrogen cyanide, it is diluted with water until 
its concentration does not exceed one per cent. Two drops of a 
saturated solution of pure paranitrophenol are then added. If 
the solution takes on a yellow color, decinormal hydrochloric 
acid is added until the color has very nearly disappeared. On 
the other hand, if the solution remains colorless, a decinormal 
solution of potassium hydroxide is added until a very pale- 
yellow tint is observed. 15 to 20 cc. of a solution of mercuric 
chloride containing 40 grams of the pure recrystallized salt to 
the liter is then added, and the solution is stirred and is allowed 
to stand for one hour at the temperature of the air. The hydro- 
chloric acid set free in the reaction 

HgCl 2 + 2 HCN = Hg (CN) 2 + 2 HC1 

is then titrated with a decinormal solution of potassium hydrox- 
ide, the end point of the titration being shown by the appear- 
ance of a pale-yellow tint in the solution. 

HYDROGEN SULPHIDE (H 2 S) 

Properties of Hydrogen Sulphide. Specific gravity, 
1.1773; weight of one liter, 1.5230 grams. 
According to Bunsen's experiments, water absorbs: 

at 2 C., 4.2373 vol. H 2 S 
" 9.8 C., 3.5446 " " 
" 14.6 C., 3.2651 " 
" 19 C., 2.9050 " 

Between 2 and 43.3 the absorption by one volume of water at t 
= 4.3706 0.083687 t + 0.0005213 t 2 volumes of H 2 S. 

According to the same authority alcohol takes up, between i 
and 22, at temperature /, 

17.891 0.65598 t + 0.00661 t 2 volumes. 



PROPERTIES OF THE VARIOUS GASES 271 

One and a half volumes of oxygen are necessary for the com- 
bustion of one volume of hydrogen sulphide, and one volume of 
sulphur dioxide is formed. 

2 H 2 S + 3 O 2 = 2 H 2 O + 2 SO 2 . 

Potassium hydroxide and solutions of salts of several other 
metals absorb hydrogen sulphide with the formation of a sul- 
phide of the metals. 

Detection of Hydrogen Sulphide. If hydrogen sulphide is 
present in any considerable amount, its presence is disclosed by 
its odor. It may more certainly be detected by introducing into 
the gas a strip of moistened " lead-paper." Lead-paper is made 
by dipping filter paper into a solution of lead acetate, drying it 
and cutting it into narrow strips. In using it for testing for 
hydrogen sulphide it should first be moistened either with water 
or with dilute ammonium hydroxide. If hydrogen sulphide is 
present in the gas mixture, the paper becomes covered with a 
glistening brownish black layer of lead sulphide. 

Another method for the detection of hydrogen sulphide is that 
devised by Ganassini. 1 It is based upon the fact that when am- 
monium molybdate is reduced by hydrogen sulphide, the molyb- 
denum salt will react with potassium sulphocyanate to form mo- 
lybdenum sulphocyanate which when dissolved in water yields a 
solution of pinkish red color. The reagent is prepared by dis- 
solving 1.25 grams of ammonium molybdate in 50 cc. of water 
and 2.5 grams of potassium sulphocyanate in 45 cc. of water, mix- 
ing these two solutions and acidifying with 5 cc. of concentrated 
hydrochloric acid. The solution is said to be stable for some days 
if kept in a stoppered bottle and protected from the light. To 
test for the presence of hydrogen sulphide in the gas mixture the 
inside of a small porcelain evaporator is moistened with the re- 
agent, and the gas under examination is caused to impinge upon 
the moistened surface. The test may also be made by dipping a 
piece of filter paper into the reagent and holding the moistened 
1 Boll. Chim. Farm., 41 (1902), 417. 



272 GAS ANALYSIS 

paper in the gas. If hydrogen sulphide is present, the liquid or 
the paper takes on a color that varies from a pale pink to a deep 
pinkish red according to the amount of hydrogen sulphide in the 
gas. Neither acetylene nor sulphur dioxide produces the red 
coloration. 

Determination of Hydrogen Sulphide. Hydrogen sulphide 
may quantitatively be determined by Dupasquier's method, a 
measured quantity of gas being drawn through a solution of 
iodine in potassium iodide, to which some starch paste has been 
added. The operation is stopped as soon as the solution be- 
comes colorless. The reaction is 

H 2 S + 2 I = 2 HI + S, 

but the reaction follows this equation precisely only when the 
solutions are very dilute and are protected from direct sun- 
light 

R. Fresenius 1 determines hydrogen sulphide gravimetrically 
by first drying the gases with calcium chloride and then absorb- 
ing the hydrogen sulphide in U-tubes which are filled with 
pumice-stone impregnated with copper sulphate, and ^, at the 
exit end, with calcium chloride. The pumice-stone is prepared 
as follows: Place 60 grams of pumice-stone, in pieces the size of 
a pea, in a small porcelain dish, and pour a hot concentrated 
solution of from 30 to 35 grams of copper sulphate over it. 
Evaporate the solution to dry ness with constant stirring, place 
the dish in an air- or oil-bath, whose temperature is kept between 
150 and 1 60 C., and let it remain there four hours. 

A tube containing 14 grams of this copper sulphate pumice- 
stone takes up about 2 grams of hydrogen sulphide. To make 
sure of complete absorption two such tubes should always be 
used. When the pumice-stone is less thoroughly dried, it takes 
up a much smaller amount of hydrogen sulphide, and when it 
has been dried at a higher heat until the copper sulphate has 

1 R. Fresenius, Anleitung zur quant. Analyse, 6th ed., Part I, p. 505. Also Zeitschr. 
f. analyt. Chentie, 10 (1871), 75. 



PROPERTIES OF THE VARIOUS GASES 273 

lost its water of crystallization it causes decomposition of the 
hydrogen sulphide and evolution of sulphur dioxide. 

SULPHUR DIOXIDE (SC^) 

Properties of Sulphur Dioxide. Specific gravity, 2.2131; 
weight of one liter, 2.8611 grams. 

Sulphur dioxide is easily soluble in water. According to Sims, 
i volume of water dissolves at 760 mm. pressure 

at 7, 61.65 vol. SO 2 
" 20, 36.43 " " 
" 39-8, 20.5 " " 
" 50, 15.62 " 

One volume of water absorbs at 760 mm. pressure, and at tem- 
peratures between o and 20, at /, 

79.789 2.6077 ^ + - 2 9349 i 2 

volumes of sulphur dioxide; and i volume of the saturated 
aqueous solution contains, at /, 

68.861 1.87025 / + 0.01225 ^ 

volumes of the acid. 

For temperatures between 21 and 40, the coefficient of 
absorption is 

75.182 2.1716 t + 0.01903 t 2 , 

and the amount of gas contained by the saturated aqueous 
solution is 

60.952 1.38898 i + 0.00726 / 2 volumes. 

One volume of alcohol absorbs at 760 mm. pressure and t, 
328.62 16.95 ^ + -3 II 9 P volumes of sulphur dioxide. 

The alcoholic solution of sulphur dioxide, saturated at o, 
contains 216.4 volumes of the gas. 

The gas reddens moist blue litmus paper. 



274 GAS ANALYSIS 

The gas is readily absorbed by solutions of the hydroxides of 
the alkali metals. 

Determination of Sulphur Dioxide. Sulphur dioxide is 
determined either by leading a measured volume of the gas 
through a solution of bromine in water, and precipitating the 
sulphuric acid thus formed by barium chloride, or by measuring 
the amount of gas required to decolorize an iodine solution of 
known strength, 

SO 2 + 2 I + 2 H 2 O = H 2 SO 4 + 2 HI. 

This latter method is very generally employed for the de- 
termination of sulphur dioxide in "burner gas," the usual pro- 
cedure being that recommended by Reich. 1 The operation may 
be carried out in the apparatus shown in Fig. 25. A is a Fried- 
rich's spiral gas washing bottle, B is a glass bottle of about three 
liters capacity and C is a 250 cc. graduated cylinder. 10 cc. of a 
standard solution of iodine containing 12.692 grams of iodine 
to the liter is poured into A. 65 cc. of water is then added to- 
gether with sufficient of a starch solution to give to the liquid 
an intense blue color. B is rilled nearly to the top with water 
and the siphon tube D is filled with water by applying suction 
at its lower end. The apparatus is then connected as shown 
in the figure and the inlet tube of A is joined by glass tubing 
to the chamber or pipe from which the gas is to be drawn. The 
screw pinchcock E is now opened and water is allowed to run 
out of B until a gas bubble starts to rise in the absorption bot- 
tle A. The graduated cylinder is then placed under the end of 
D and the water that flows from B is collected in it. In this 
manner the gas is slowly aspirated through the iodine solution 
until the liquid is decolorized. The pinchcock E is then at once 
closed and the volume of water that has collected in the gradu- 
ated cylinder is measured. 

The amount of sulphur dioxide in the mixture under examina- 

1 F. Reich, Berg-und Huttenmdnn. Zeitung, 1858. 



PROPERTIES OF THE VARIOUS GASES 275 

tion may then be calculated as follows: One cc. of the standard 
iodine solution corresponds to 0.0032 gram SO2 which amount 
under standard conditions possesses a volume of 1.118 cc. If 
b equals the prevailing barometric pressure, / the temperature, 
h the difference in height in millimeters between the level of 
the water in B and the lower end of the siphon tube D, and n 
the cubic centimeters of iodine solution employed, then the ac- 
tual volume under the prevailing conditions of the sulphur 
dioxide, s, that has passed through the iodine solution may be 
calculated by use of the following formula: 

s = 1.118 X n X - 7 ^ X (i + 0.00367 t) cc. 



The volume of the water, w, in the graduated cylinder C is 
equal to the amount of gas that has been drawn through A 
exclusive of the volume of sulphur dioxide; consequently the 
total volume of gas drawn into A equals w -\- s and the per cent 

of sulphur dioxide in the gas mixture equals - 

If it should not be deemed necessary to introduce correc- 
tions for the pressure and temperature, the formula becomes 

m.Sxn 

= per cent 862. 



w + 1.118 x n 

If 10 cubic centimeters of the standard (decinormal) iodine 
solution is used, the volume percentage of sulphur dioxide in 
the original gas mixture that is indicated by different volumes of 
water collected in the graduated cylinder is shown in the table 
on page 276. l 

An apparatus that \$ based upon the same principle as that 
of Reich, but which is so constructed that the per cent of sul- 
1 Lunge, Sulphuric and Alkali, 1903, vol. i, part i, p. 415. 



276 GAS ANALYSIS 

CUBIC CENTIMETERS WATER VOLUME PER CENT SO 2 

COLLECTED IN KILN GAS 

82 12 

86 II. 5 

90 II 

95 io-5 

ICO 10 

106 9.5 

US 9 

i 20 8.5 

128 8 

138 7-5 

148 7 

i 60 6.5 

175 6 

192 5-5 

212 5 

phur dioxide in the gas mixture may be directly read off, has 
been described by Kreidl. 1 

Determination of Sulphur Dioxide in presence of Nitrous 
Acid. The method of Reich cannot be used for the determina- 
tion of sulphur dioxide in the gases from the lead chambers of the 
sulphuric acid process because the hydriodic acid that is formed 
is quickly oxidized again to iodine by the nitrous acid that is 
present. The iodine that is thus set free then oxidizes additional 
amounts of sulphur dioxide with the result that the percentage 
of sulphur dioxide in the gas mixture appears to be much smaller 
than it actually is. Moreover, the presence of nitrous acid ren- 
ders the end point of the reaction, the decolorization of the iodine 
solution, uncertain for the reason that after decolorization has 
been effected by the sulphur dioxide the blue color reappears 
because of the action of the nitrous acid. For the determination 
of sulphur dioxide in the presence of nitrous acid, it is conse- 
quently necessary to modify the method in such manner as to 
prevent the interference of nitrous acid and this is accomplished 
by Raschig 2 by adding sodium acetate to the solution. This 

1 Z.f. Zuck,-Ind. Bohm., 24 (1900), 658. 

2 Z./. angewandte Chern., 22 (1909), 1182. 



PROPERTIES OF THE VARIOUS GASES 277 

reacts with the free nitrous acid to form sodium nitrite and with 
the sulphur dioxide to form sodium sulphite, and these two salts 
do not act upon each other. 

In the Raschig method the absorption bottle A } Fig. 25, 
contains 10 cc. of decinormal iodine solution, about 60 cc. of 
water, a little starch solution and 10 cc. of a cold saturated solu- 
tion of sodium acetate. A U-tube or bulb tube containing 
cotton is placed between A and the lead chambers to prevent 
sulphuric acid from passing into the iodine solution. The amount 
of sulphur dioxide in the gas mixture is determined in the manner 
already described under the Reich method. The nitrous acid 
in the gases may then be determined by rinsing out the contents 
of the absorption bottle A into a flask, adding a drop of phenol- 
phthalein, and titrating the free acetic acid with a decinormal 
solution of sodium hydroxide. From the volume of the sodium 
hydroxide solution used, there is to be subtracted 10 cc. for the 
hydriodic acid resulting from the reduction of the 10 cc. of deci- 
normal iodine solution, and also 10 cc. more for the sulphuric 
acid formed in the reaction (see page 274). The balance of the 
sodium hydroxide that is used indicates free nitric acid or nitrous 
acid. Raschig states that while the method gives satisfactory 
results for sulphur dioxide, it is not very exact for the determina- 
tion of the oxides of nitrogen if the gas sample is taken from the 
beginning of the lead chambers, because here the sulphur dioxide 
is present in preponderating amount. If, however, the gas 
sample is taken from the end of the chamber system where the 
oxides of nitrogen are present in much larger proportion, a pro- 
portionately larger sample of the gases will be needed to de- 
colorize the iodine solution and a determination of the oxides 
of nitrogen will be correspondingly more exact. 

CARBON OXYSULPHIDE (COS) 

Properties of Carbon Oxysulphide. Specific gravity, 
2.0749; weight of one liter, 2.6825 grams. 
Pure carbon oxysulphide has no odor, and its freshly prepared 



2 7 8 



GAS ANALYSIS 



solution in water has no taste. Its action upon the nervous 
system is somewhat similar to that of nitrous oxide. 1 When 
inhaled for a few seconds it causes dizziness and buzzing in the 
ears, but if the inhalation is not continued, the symptoms quickly 
disappear. 

Water absorbs about one-third 2 of its own volume of the gas. 

A solution of potassium hydroxide absorbs carbon oxysulphide 
very slowly, but the gas is rapidly taken up by a solution pre- 
pared by dissolving one part of potassium hydroxide in two parts 
of water and adding an equal volume of alcohol. The analyt- 
ical absorbing power of this solution is 18; that is, a cubic 
centimeter of this reagent is able to absorb 72 cc. of carbon 
oxysulphide. The gas is but slightly soluble in a hydrochloric 
acid solution of cuprous chloride, i cc. of this solution absorbs 
about 0.2 cc. of the gas. 

Experiments made by Hempel 3 upon the analytical absorb- 
ing power of various reagents for carbon oxysulphide, hydrogen 
sulphide, and carbon bisulphide gave the following results: 





ANALVTI 


CAL ABSORBINC 


; POWER 


REAGENT EMPLOYED 


Carbon 
Oxysulphide 


Hydrogen 
bulpnide 


Carbon 
Bisulphide 










Chloroform 
A/r,Vt, > ) T P art triethylphosphine . 


I 




2 3 
-ff. 


Ml * ture i 9 parts chloroform . . . 
Pyridinc 


I ' 
I . I 


4-5 




( i part triethylphosphine . 
Mixture < 9 parts pyridine . . . 
( 10 parts nitrobenzene 
Nitrobenzene 
i part potassium hydroxide in 2 parts 
water. One-half saturated with H2S, 


( 3 
3 


26 

2 


26 
46 


and the 2 portions then mixed 
Saturated solution of copper sulphate in 
a mixture of 200 grams water and 200 

















1 Klason, J. prakt. Chem. 36 (1887), 64. 

2 Witzeck, /. Gasbeleuchtung, 46 (1903), 145. 

3 Z.f. angewandte Chem. 1901, 865. 



PROPERTIES OF THE VARIOUS GASES 279 

Carbon oxysulphide may be separated from hydrogen sul- 
phide by absorbing the latter in an acidulated solution of copper 
sulphate (see table above). Separation from vapor of carbon 
bisulphide may be effected by passing the gases through a mix- 
ture of one part of triethylphosphine and nine parts of chloro- 
form, which absorbs the carbon bisulphide. The most delicate 
reagent for its detection is iodide of starch. If the gas is passed 
through a starch solution that is colored a clear blue by a trace 
of iodine, the color of the solution is very slowly discharged. 
The blue tint changes first to violet, then to red, and finally the 
color disappears completely. Other gases that would act upon 
the iodide of starch must of course be absent. 

One volume of carbon oxysulphide needs ij volumes of 
oxygen for its combustion and yields one volume of COz and 
one volume of SO2. 

Determination of Carbon Oxysulphide. Hempel deter- 
mines 1 carbon oxsulphide in the presence of hydrogen sulphide 
and carbon dioxide by first absorbing the hydrogen sulphide 
with an acid solution of copper sulphate, then decomposing 
the carbon oxysulphide into carbon monoxide and sulphur by 
passing the residual gas mixture through a hot capillary tube 
of platinum, determining the carbon monoxide that is here set 
free by absorption in a hydrochloric acid solution of cuprous 
chloride, and finally determining the carbon dioxide by means of 
potassium hydroxide. 

Witzeck 2 raises objections to this method and gives prefer- 
ence to the procedure proposed by Lunge, which consists in 
passing the gas mixture through an iodine solution for the re- 
moval and the determination of hydrogen sulphide, and then 
shaking the residual gas with a solution of potassium hydroxide 
which will decompose the carbon oxysulphide with the forma- 
tion of potassium sulphide and potassium carbonate. To this 
solution hydrochloric acid is then added to set free hydrogen 

1 Z. /. angewandte Chem. 1901, 865. 

2 Loc. cit. 



2 So GAS ANALYSIS 

sulphide and carbon dioxide. The hydrogen sulphide is deter- 
mined by means of an iodine solution and the carbon dioxide is 
determined by absorption with potassium hydroxide. Since one 
volume of carbon oxysulphide yields upon decomposition one 
volume of hydrogen sulphide and one volume of carbon dioxide, 
the amount of carbon dioxide present in the original mixture 
is ascertained by subtracting from the volume of carbon dioxide 
formed, a volume equal to that of the hydrogen sulphide found 
to be present. 

Carbon oxysulphide cannot be present in washed illuminating 
gas because as Witzeck points out it will be completely decom- 
posed by the water vapor with which it comes in contact. Even 
if it should partially escape decomposition by water it would 
react very rapidly with ammonia or with ammonium hydroxide 
to form ammonium thiocarbamate, 

~ /ONH 4 



S=C =0 + 3 , 

Vlv 



FLUORINE Ft) 

Determination of Fluorine. O. W. F. Oettel devised a 
method for the determination of fluorine in a substance, the 
fluorine being evolved as silicon tetrafluoride, and the volume 
of this gas then being directly measured. Since a large number 
of substances contain both fluorine and carbon dioxide, Hempel 
and W. Scheffler 1 have modified the method to permit of the 
simultaneous determination of fluorine and carbon dioxide in a 
single sample. 

The fluorine is set free as silicon tetrafluoride together with 
carbon dioxide in a suitable apparatus, is collected in a burette, 
and the silicon tetrafluoride is then decomposed and absorbed 
by means of water (a small volume of carbon dioxide is here 
taken up by the water). The carbon dioxide still present in the 
gas is then completely removed by passing the gas into a pipette 
containing caustic potash. The gas residue is again brought 

1 Z.f. anorg. Chem., 20 (1899), i. 



PROPERTIES OF THE VARIOUS GASES 281 

over the water which was first used and by which the silicon 
tetrafluoride was absorbed; the absorbed carbon dioxide here- 
upon escapes from the water and passes into the gas residue. 
Upon transferring the gas once more to the caustic potash pi- 
pette, the remainder of the carbon dioxide is removed, and this 
volume is subtracted from the diminution first obtained by the 
absorption with water. The difference gives the amount of sili- 
con tetrafluoride. In this manner it is possible to make very 
sharp determinations of fluorine in the presence of carbon 
dioxide. 

For setting free the silicon tetrafluoride there is used the ap- 
paratus shown in Fig. 87, II. The evolution flask is connected 
with a simple gas burette filled with mercury and containing on 
top of the mercury some concentrated sulphuric acid. It is well 
to join to the burette a level-bulb instead of a level-tube, and to 
attach a glass stopcock to the lower end of the burette tube 
(see Fig. 87). 

The substance under examination is mixed with finely pow- 
dered quartz, the weight of the quartz being fifteen times that 
of the fluorine which is probably present in the material. The 
quartz is first heated for a long time in a muffle furnace with 
free access of air to remove every trace of organic matter. 

The sulphuric acid to be employed must be freed from or- 
ganic substances and from oxides of nitrogen. This is ac- 
complished by adding to concentrated sulphuric acid about 
5 grams of powdered sulphur and then fuming down the acid to 
two-thirds of its original volume. 

In carrying out a determination the evolution flask II is first 
carefully dried and the substance, together with the proper 
amount of quartz powder, is then introduced into the flask by 
means of a long weighing tube, and the two powders are mixed 
as intimately as possible by shaking the flask. The flask is then 
joined by means of the capillary d and a piece of dry rubber 
tubing to the gas burette I which contains mercury and some 
sulphuric acid, as above described. The rubber tube is held 



282 



GAS ANALYSIS 



firmly in place by means of ligatures of light wire. The vol- 
ume of concentrated sulphuric acid which is placed in the bu- 
rette amounts to only about 0.25 cc. Its presence is necessary 
to avoid the possibility of decomposition of the silicon tetra- 
fluoride by any moisture that might be in the burette. 

ST 




FIG. 87 

In the bells I and m is placed some of the highly concentrated 
sulphuric acid. A water suction pump is now connected to k, 
and the flask II is partially exhausted. The stopcock n is then 
closed, and upon lifting the tube o sulphuric acid flows down 
from m into the flask. The flask is shaken so as to bring the 
acid into intimate contact with the mixture of quartz and the 



PROPERTIES OF THE VARIOUS GASES 



283 



substance, and the contents of the flask is then heated fully up 
to the boiling-point of sulphuric acid, the heating being con- 
tinued for about fifteen minutes. 

If the apparatus should break, the operator might be seriously 
injured by the hot concentrated sulphuric acid. It is well, 
therefore, to protect the eyes with goggles, and to place a glass 
screen between the flask and the operator. 

The heating is now stopped, 
and the gas in the flask is com- 
pletely driven over into the 
burette by filling m with con- 
centrated sulphuric acid and 
carefully lifting the tube o. 
The flask is then disconnected 
from the burette and the total 
volume of the gas is measured. 

The burette is now con- 
nected in the ordinary man- 
ner, by means of a capillary 
tube, with a simple mercury 
absorption pipette of the form 
shown in Fig. 88, the pipette 
containing 5 cc. of water above 
the mercury. The gas is trans- 
ferred to the pipette and 
shaken for five minutes with F IG . gg 

the water. It is then brought 
back into the burette and the diminution in volume is read off. 

The remaining gas is passed into a pipette filled with a solu- 
tion of potassium hydroxide to absorb carbon dioxide, and is 
then drawn back into the gas burette. The volume is observed, 
and the gas is now passed into the first pipette, Fig. 88, and 
shaken again for three minutes. It is then passed back into 
the burette, and the residual volume of gas is measured. This 
gas is then passed once more into the potassium hydroxide 




284 



GAS ANALYSIS 



pipette to determine the small amount of carbon dioxide which 
was taken up by the water used in the first absorption of the 
silicon tetrafluoride. 

All of these operations can be carried out with considerable 
speed, and it is therefore easily possible to make a determination 
of fluorine in two hours. 

As an example of the accuracy of the method, the following 
result may be cited: 2.156 grams of the substance gave 3.56 cc. 
of silicon tetrafluoride, while theory called for 3.45 cc. 

To illustrate the application of the method to the analysis 
of teeth, a few results of determinations of fluorine in teeth ash 
are tabulated below. 

The incineration of teeth is easily effected in a hard glass tube 
in a current of oxygen if the powder is very fine and is placed 
in the tube in a very thin layer. 

In determining fluorine in material that contains organic 
matter, it is very important that the substance should be com- 
pletely incinerated, since the slightest trace of residual carbon 
would act upon the boiling sulphuric acid and cause the forma- 
tion of sulphur dioxide, a gas which would then be absorbed by 
water when the silicon tetrafluoride is determined. 











CO2 


SiF4 




Per cent 


HUMAN 
TEETH 


Grams 
of 
Teeth 
Ash 
taken 


SiF4 
+ 
C02 
found 


CO2 


which 
was 
taken up 
by the 
water 


in 
cubic 
centi- 
meters 


Fluorine 
in 
Grams 


of 
Fluorine 
in the 
Teeth 
Ash 


Unsound 


1-793 


I .O 


4-65 




1.0 


0.0034 


O.IQ 


Sound 


1-434 


i-5 


5-8o 


O.I 


1.4 


0.0047 


0-33 


Sound 


0.831 


1.6 


3-50 




1.6 


0.0054 


0.52 



CHLORINE (C1 2 ) 

Properties of Chlorine. Specific gravity, 2.4494; weight of 
one liter, 3.166 grams. 

Chlorine is quite soluble in water. One part of cold water 



PROPERTIES OF THE VARIOUS GASES 285 

dissolves approximately two volumes of chlorine; hot water 
dissolves less. According to Schonfeld, one volume of water 
absorbs the following volumes of chlorine: 

10, 2.5852 
15, 2.3681 

20, 2.1565 
25, 1.9504 
30, 1.7499 

35, 1-5550 
40, 1.3656. 

Determination of Chlorine. Chlorine may be determined 
by the Bunsen procedure, in which the gas is led through a solu- 
tion of potassium iodide, and the iodine set free is titrated with 
sodium thiosulphate : 

C1 2 + 2 KI = 2 KC1 + 2 I 

2 Na 2 S 2 O 3 + 2 I = Na 2 S 4 O 6 + 2 Nal. 

Chlorine is absorbed by potassium hydroxide or sodium 
hydroxide. In cold dilute solutions the hypochlorite and 
chloride of the alkali are formed : 

2 KOH + C1 2 = KC1O + KC1 + H 2 O. 
In hot concentrated solutions, the reaction is: 

6 KOH + 3 C1 2 =5 KC1 + KC1O 3 + 3 H 2 O. 

The first of these two reactions was used by Treadwell in the 
determination of chlorine in the presence of carbon dioxide, but 
Offerhaus 1 found that even with a very dilute solution of sodium 
hydroxide an appreciable amount of sodium chlorate is formed, 
and that for this reason the titration of the hypochlorite with 

arsenious acid gives results about 0.7 per cent too low. 

1 Z.f. angewandte Chem., 16 (1903), 1033. 



286 GAS ANALYSIS 

Offerhaus obtained very satisfactory results by passing the 
mixture of chlorine and carbon dioxide through two dry Bunte 
burettes connected in series, determining chlorine in the first 
burette by absorbing the gas with a solution of potassium iodide 
and titrating the liberated iodine, and in the second burette 
determining the total amount of chlorine and carbon dioxide by 

absorption of the two gases with sodium hydroxide. The 

difference between the two results gives the amount of carbon 
dioxide. 

To avoid the use of two gas burettes, Treadwell and Christie l 
absorb the chlorine in a decinormal solution of primary potas- 
sium arsenite, KH^AsOs, and directly afterward determine the 
carbon dioxide in the gas mixture by absorption with a solution 
of potassium hydroxide. 

They used a water- jacketed Bunte burette with a tail-stopcock 
at G (see Fig. 43) as well as at C, and with the upper part of 
the burette narrow to render more accurate the reading of small 
residual gas volumes. The burette is cleaned and thoroughly 
dried, and the gas mixture is then passed into the burette 
through the end of the lower stopcock and out through the upper 
stopcock, the passage of the gas being continued until all of the 
air that was originally in the burette has been displaced. The 
lower stopcock is then closed and after ten seconds the upper 
stopcock is closed and the barometric pressure and temperature 
of the water surrounding the burette are noted. The lower 
stopcock is then turned so that the upper end of the stopcock 
communicates with the tube H from the level-bottle B. Tread- 
well and Christie use a level-tube in place of the level-bottle. 
The level-tube is filled with distilled water and this is allowed to 
flow through the rubber tube H and out through the end of the 
lower stopcock G to expel air from the tube and chlorine from 
the end tube and lower stopcock. When the water has flowed 
out of the level-tube and only the connecting rubber tube H is 

1 Z. /.. angewandte Chem., 18 (1905), 1930. 



PROPERTIES OF THE VARIOUS GASES 287 

filled with water, the stopcock G is closed and there is poured 
into the level-tube exactly 100 cc. of a decinormal solution of 
primary potassium arsenite. This solution is prepared by dis- 
solving 4.95 grams of arsenic trioxide in a dilute solution of 
potassium hydroxide, adding phenolphthalein and then sul- 
phuric acid until the color of the solution disappears, and finally 
diluting to one liter. The lower stopcock is then turned so that 
the level-tube communicates with the burette. The arsenite 
solution at first rises rather slowly in the burette, but later its 
passage is more rapid. Toward the close of the absorption of 
the chlorine, the burette is shaken to hasten the completion of 
the reaction. 

After the absorption of the chlorine has been effected, which 
takes about 5 minutes, the liquid in the two tubes is brought to 
the same height and the volume of gas remaining in the burette 
is read off. The level-tube is now lowered, 10 cc. of a solution of 
potassium hydroxide (i 12) is poured into the funnel D, the upper 
stopcock C is carefully opened and the solution drawn down into 
the burette. The stopcock is then closed, the burette is shaken 
to hasten the absorption of the carbon dioxide, the liquid in the 
burette and level-tube is brought to the same height and the 
residual gas volume is read off the temperature and barometric 
pressure being again noted. 

All of the liquid in the level-tube and in the burette is then 
transferred to an Erlenmeyer flask and the apparatus thoroughly 
rinsed with water which is also added to the contents of the flask. 
Some phenolphthalein is then added to the solution and dilute 
hydrochloric acid (1:4) is run in until the red color of the liquid 
just disappears. 60 cc. of a solution of sodium bicarbonate 
containing 40 grams of the salt to the liter is then added to- 
gether with a little starch solution, and the excess of arsenious 

acid is determined by titration with ^ solution of iodine. 

In calculating the results, allowance must be made for the fact 
that the original mixture of chlorine and carbon dioxide is 



288 GAS ANALYSIS 

usually practically free from moisture, while the gas residue in 
the burette is measured in the moist condition. The volume 
which the residual gas would occupy if dry and at the pressure 
and temperature under which the gas sample was measured 
must consequently first be calculated. The difference between 
this volume and the original volume of the sample in the burette 
will give the total amount of chlorine and carbon dioxide. The 
amount of chlorine may be read off after the absorption of that 
gas by the arsenite solution and the correction of the residual 
volume, or it may be determined by titration with an iodine 

solution as above mentioned. One cc of an -- solution of 

10 

iodine corresponds to 0.003546 gram chlorine, and this weight 
of chlorine under standard conditions will occupy a volume of 
1.1015 cc< 

Treadwell and Christie state that the determination of chlorine 
by absorption with the arsenite solution agrees quite closely 
with the results obtained by titration, the average difference 
amounting to 0.13 per cent. 

If a solution contains free chlorine together with hydro- 
chloric acid, they may both be determined in the following 
manner (Fresenius) : 

To a weighed portion of the liquid add an aqueous solution of 
sulphurous acid until the latter is in excess ; after some time add 
nitric acid and then some potassium chromate to destroy the 
excess of sulphur dioxide, and precipitate the total chlorine as 
silver chloride. 

If now the amount of free chlorine is determined in a second 
portion by potassium iodide, the difference gives the quantity 
of chlorine present in the form of chloride. 

The total chlorine may be volumetrically determined by ab- 
sorbing the gases with a solution of sodium hydroxide, adding 
sulphur dioxide, then, after a while, nitric acid and some potas- 
sium chromate, and finally neutralizing the solution by adding 
calcium carbonate. All chlorine is now present as chloride, and 



PROPERTIES OF THE VARIOUS GASES 



289 



the solution is neutral, so that the chlorine may be titrated with a 
neutral silver solution, potassium chromate being used as in- 
dicator. 

HYDROGEN CHLORIDE (HC1) 

Properties of Hydrogen Chloride. Specific gravity, 1.2595; 
weight of one liter, 1.6283 grams. 

According to Roscoe and Dittmar, one volume of water dis- 
solves at o, 503 volumes of hydrogen chloride. The parts by 
weight of the gas which dissolve in one gram of water at a 
pressure of 760 mm. and at different temperatures, are given in 
the following table: 



TEMPERATURE 


HC1 


TEMPERATURE 


HC1 


O 


0.825 


32 


0.665 


4 


0.804 


36 


0.649 


8 


0.783 


40 


0.633 


12 


0.762 


44 


0.618 


16 


0.742 


48 


0.603 


20 


0.721 


52 


0.589 


24 


0.700 


56 


0-575 


28 


0.682 


60 


0.561 



At ordinary temperatures, one volume of alcohol dissolves 327 
volumes of hydrogen chloride. 

Determination of Hydrogen Chloride. If no other acid gas 
is present with the hydrogen chloride, it may be determined by 
drawing a measured quantity of the gas through a standardized 
solution of an alkali and titrating back with an acid. 

Hydrogen chloride may also be determined by absorbing it 
with an alkaline solution free from chlorine, and, after acidifying, 
precipitating it with silver nitrate, and weighing as silver chlo- 
ride. 

A method proposed by Cl. Winkler, 1 and based upon J. Vol- 
hard's volumetric method for the determination of silver, 2 con- 

1 Cl. Winkler, Anleitung zur Untersuchung der Industrie-Case, Part II, p. 322. 

2 J. Volhard, Zeitschrijt fur andyt. Chemie, 13 (1874), 171, and 17 (1878), 482. 



2 9 o GAS ANALYSIS 

sists in placing in a suitable absorption apparatus a few drops 
of ammonium sulphocyanate or potassium sulphocyanate, some 

iron alum solution, and a measured amount of silver nitrate 

10 

solution. Upon leading the gas through this solution the hydro- 
chloric acid reacts with the silver, forming silver chloride. The 
end of the reaction is shown by the blood-red color. The ap- 
pearance of this color is due to the fact that after all of the sil- 
ver nitrate has been changed to silver chloride, the silver sul- 
phocyanate present is also decomposed and ferric sulphocyanate 
is formed. The volume of the gas is measured and the amount 
of hydrogen chloride that it contains is calculated. 

SILICON TETRAFLUORIDE (SiF 4 ) 

Specific gravity, 3.60; weight of one liter, 4.663 grams. 

The gas is completely absorbed by water, and is at the same 
time decomposed 

3 SiF 4 + 4 H 2 O = Si (OH) 4 + 2 H 2 SiF 6 . 

This reaction, which has been employed by R. Fresenius 1 
for the quantitative determination of fluorine, might possibly 
be made use of for the determination of silicon tetrafluoride in 
gases. 

PHOSPHINE (PH 3 ) 

Properties of Phosphine. Specific gravity, 1.175; weight of 
one liter, 1.52 grams. 

Phosphine is a colorless gas with a very unpleasant odor re- 
sembling that of decayed fish. It is very poisonous. The pure 
gas takes fire only at a temperature above 100 . It can be mixed 
with pure oxygen without change, but if the mixture be sud- 
denly brought under diminished pressure, it explodes. Phosphine 
takes fire when brought in contact with a drop of fuming ni- 
tric acid, or w r ith chlorine or bromine. 

1 Fresenius, Quant, chemische Analyse, 6th ed., Part I, p. 431. 



PROPERTIES OF THE VARIOUS GASES 291 

Phosphine is somewhat soluble in water. One volume of water 
absorbs about 0.02 volume of the gas, and takes on its odor and 
a disgusting taste. Exposed to the light, the solution decom- 
poses with evolution of hydrogen and separation of amorphous 
phosphorus. The gas is decomposed by the electric spark into 
phosphorus and hydrogen. 

When a strip of silver nitrate test paper is brought into con- 
tact with the gas, the paper is at once blackened, metallic silver 
and phosphoric acid being formed. 

If phosphine is passed through a neutral aqueous solution 
of potassium mercuric iodide, a crystalline, orange-yellow pre- 
cipitate, PHg 3 I 3 , is produced. 1 

Determination of Phosphine. Phosphine may be deter- 
mined by converting it into phosphoric acid either by burning 
it or by passing it through bromine water or a solution of sodium 
hypochlorite and precipitating the resulting phosphoric acid 
with magnesia mixture. These reactions may also be utilized 
for the detection of phosphine in a gas mixture, the phosphoric 
acid being identified by precipitation with ammonium mo- 
lybdate. 

Further details concerning the determination of phosphine, 
particularly in the presence of acetylene, are given on p. 360. 

ARSINE (AsH 3 ) 

Properties of Arsine. Specific gravity, 2.696; weight of one 
liter, 3.485 grams. 

Arsine is a colorless gas of very unpleasant odor. It is ex- 
tremely poisonous. When passed through a highly heated 
tube, the gas is decomposed and a glistening mirror of metallic 
arsenic is deposited. The gas is slightly soluble in water. 

The best confining liquid for gas mixtures that may contain 
arsine is a freshly boiled concentrated solution of sodium chlo- 
ride. Arsine is completely and rapidly absorbed by solutions of 

1 Lemoult, Compt. rend., 139 (1904), 478. 



292 GAS ANALYSIS 

silver nitrate. The* reaction with dilute neutral silver nitrate or 
with a slightly acid solution of this salt does not quantitatively 
proceed according to the Lassaigne 1 reaction 

AsH 3 + 6 AgNO 3 + 3 H 2 O = H 3 AsO 3 + 6 Ag + 6 HNO 3 
but in part follows the equation: 

AsH 3 + 3 AgNO 3 = AsAg 3 + 3 HN0 3 . 

In the presence of an excess of silver nitrate the silver ar- 
senide formed in the preceding reaction gradually undergoes 
change as follows: 

AsAg 3 + 3 AgNO 3 + 3 H 2 = H 3 AsO 3 + 6 Ag + 3 HNO 3 . 

In dilute ammoniacal silver solution three reactions appear to 
occur: 

(a) AsH 3 + 3 (AgNH 3 ) N0 3 = AsAg 3 + 3 NH 4 N0 3 , 

(b) AsAg 3 + 3 (AgNH 3 ) NO 3 + NH 4 OH + H 2 O - 

NH4AsO 2 + 6 Ag -f 3 NH4NO 3 , 

(c) NH 4 As0 2 + 2 (AgNH 3 ) NO 3 + 2 NH 4 OH = 

(NH 4 ) 3 As0 4 + 2 Ag + 2 NH 4 N0 3 . 

If, however, the solution is heated for some time after absorp- 
tion, the end reaction may be expressed by the equation: 

AsH 3 + 8 (AgNH 3 ) NO 3 + 3 NH 4 OH + H 2 O = 
(NH 4 ) 3 AsO 4 + 8 Ag + 8 NH 4 NO 3 . 

When metallic arsenic stands in contact with an ammoniacal 
silver solution and the solution is warmed, the arsenic is oxidized 
to arsenic acid. 2 

As + 5 (AgNH 3 ) N0 3 + 3 NH 4 OH + H 2 O = 
(NH 4 ) 3 As0 4 + 5 Ag + 5 NH 4 NO 3 . 

1 J. chim. medic., 16 (1840), 685. 

2 Most of the above details are from the article by Reckleben, Lockemann and 
Eckardt, Z.f. analyt. Chetn., 46 (1907), 671. 



PROPERTIES OF THE VARIOUS GASES 293 

Detection of Arsine. Arsine may be detected by allowing 
the gas to act upon a crystal of silver nitrate. If the amount 
of arsine in the gas mixture under examination is not too 
great, there is formed a yellow compound which is said to be 
AsAg 3 - 3 AgNO 3 . If the gas contains considerable arsine, the 
yellow color appears only for an instant and changes to black 
almost immediately. If the gas mixture contains hydrogen 
sulphide, this is removed by passing the gases through a glass 
tube that contains first a plug of cotton, then a second plug of 
cotton that has been moistened with a solution of ammonium 
lead acetate, and beyond this a crystal of silver nitrate and one 
of lead acetate. The latter serves to show whether any hydro- 
gen sulphide has passed the second cotton plug. 

Arsine may also be detected 1 by passing the gas into a rather 
concentrated ammoniacal silver solution which is at once 
darkened by the slightest traces of the gas. The test does not 
serve to detect arsine in the presence of stibine, phosphine, or 
hydrogen sulphide, because those gases also cause a darkening 
of the silver solution. 

Determination of Arsine. Arsine cannot accurately be de- 
termined by passing the gas into a solution of silver nitrate and 
ascertaining either the amount of silver precipitated or of ar- 
senious acid formed. 2 It may, however, be volumetrically de- 
termined by absorbing the gas with a neutral solution of silver 
nitrate or with a solution of sodium hypochlorite containing 
three per cent of active chlorine. 

STIBINE (SbH 3 ) 

Specific gravity, 4.33; weight of one liter, 5.6 grams. 

Stibine is a colorless gas of less pronounced odor than arsine. 
It is but slightly soluble in water. 

When stibine is passed into a solution of silver nitrate a black 
precipitate, SbAg 3 , is formed. If this substance is washed with 

1 Reckleben and Lockemann, Z.f. angew. Chcm., 19 (1906), 275. 

2 Reckleben and Lockemann, loc. cit. 



294 GAS ANALYSIS 

water and boiled with tartaric acid, it is decomposed with the 
formation of silver and a soluble compound of antimony. 

When stibine acts upon a crystal of silver nitrate, the black 
compound, SbAg 3 , is formed. 

Stibine may be determined by passing the gas into a solution 
of silver nitrate, collecting the silver antimonide on a filter, 
washing it, decomposing it with tartaric acid and determining 
the antimony in solution. 



CHAPTER XIV 
FLUE GAS ANALYSIS 

In the examination of the efficiency of the various devices in 
which the chemical energy of the fuel is transformed into heat 
energy, it is usually necessary to determine the composition and 
the heating value of the fuel, and to make an analysis of the gas 
mixture that passes from the zone of combustion into the flue. 
The analysis of solid and liquid fuels does not fall within the 
scope of the present work, but the analysis of flue gas will here 
be considered, and the determination of the heating value of 
solid, liquid and gaseous fuel and the analysis of combustible 
gas mixtures will be discussed in later chapters. 

When carbon is burned in air, one volume of oxygen unites 
with solid carbon to form one volume of carbon dioxide. If pure 
carbon could be completely burned with an amount of air that 
contains oxygen just sufficient for the conversion of the carbon 
to carbon dioxide, the escaping gases would contain the same 
amount of carbon dioxide as there is oxygen in the air, namely, 
about 21 per cent. The combustible matter in commercial fuels 
does not, however, consist entirely of pure carbon, and con- 
sequently the theoretical amount of carbon dioxide that would 
be formed in their complete combustion will always lie below 
21 per cent. If the attempt should be made in actual practice 
to cut down the air supply to the amount theoretically needed 
for the combustion of the fuel, incomplete combustion would 
result. The amount of air admitted to the fuel is, in proper 
firing, from one and a half to two times that theoretically neces- 
sary, with the result that the percentage of carbon dioxide in the 
flue gas will range from about nine to fourteen per cent. With 
careless firing or faulty construction of the furnace the per cent 

295 



296 GAS ANALYSIS 

of carbon dioxide in the flue gas will fall below the above amount 
and the per cent of oxygen in the escaping gases will correspond- 
ingly rise. The greater the excess of air admitted to the furnace 
the larger will be the amount of heat carried off through the flue 
by the gases. 

In the analysis of flue gas, it is at times sufficient to determine 
merely the carbon dioxide in the gas mixture. Usually, how- 
ever, as in a boiler test, it is necessary to determine both carbon 
dioxide and oxygen (and also carbon monoxide if present, al- 
though this is rarely the case). 

Sampling of Flue Gas. If the operator wishes merely to 
ascertain the percentages of these three gases in the flue gases at 
certain intervals, the gases from the fire may be drawn by a 
bottle aspirator through a tube provided with a T-tube (see 
Fig. 7) to which a gas burette is attached in the manner shown. 
Any other aspirating device may of course be employed in place 
of the bottle aspirator. It is inadmissible to collect or store over 
water any gas mixture containing carbon dioxide if, in the de- 
termination of that gas, results of more than approximate ac- 
curacy are desired. The small bottle E contains a little water 
which serves to wash the flue gases and to indicate their speed of 
flow. Before a sample of the flue gases is drawn off in the 
Hempel burette, the pinchcocks d and / are opened and the 
level-tube is raised until the confining liquid stands at c. In 
drawing off the sample for analysis, d and / are opened and the 
level- tube is slowly lowered until slightly more than 100 cc. of 
gas has been drawn into the burette. The two pinchcocks are 
then closed and the rubber tube at the top of the burette is 
slipped off the lower end of the glass tube e. If only approxi- 
mate results are required, water may be used as the confining 
liquid in the burette. For more accurate work mercury should 
be employed. 

If an average sample of the flue gases covering a period of 
several hours is desired, the sampling tube of Huntly (see p. 5) 
should be employed and the sample collected over mercury. 



FLUE GAS ANALYSIS 297 

Although Huntly gives no description of the method to be fol- 
lowed in transferring the gas from the sample tube to a Hempel 
gas burette, it is obvious that this may easily and accurately be 
done in the following manner: 

Invert the tube and fasten it in a clamp. Connect a mercury 
level-bulb with the capillary tube A by a piece of rubber tubing 
about 40 cm. long. Turn the stopcock H so that A communi- 
cates with the side capillary tube B, thus driving all air out of A. 
Connect the capillary tube F with the capillary connecting tube 
of the burette by a short piece of rubber tubing in the usual 
manner, and turn the stopcock K so that F opens into E. Open 
the pinchcock of the burette, raise the level-tube and in this man- 
ner fill F with mercury. Upon now turning the stopcock H and 
K to such positions that A and F communicate with C, and 
lowering the level-tube of the burette, the gas sample will be 
drawn over into the burette without possibility of admixture 
with air. 

Analysis of Flue Gas. If the sample of flue gas is taken in 
the neighborhood of the laboratory, the analysis may rapidly 
and accurately be made either with the form of Orsat apparatus 
devised by the author and described on p. 85, or with the ap- 
paratus of Hempel. If the latter is used, a sample of 100 cc. is 
measured off in a Hempel burette in the manner described on 
p. 59. The three gases, carbon dioxide, oxygen and carbon 
monoxide, are then absorbed in the order given, the decrease of 
volume in cubic centimeters in each case giving directly the 
percentage of the constituent in the flue. gas. 

Carbon dioxide is absorbed in a Hempel simple gas pipette 
for solid reagents that is filled with a concentrated solution of 
potassium hydroxide (see p. 225). The pipette is connected 
with the burette in the manner that has already been described 
in detail on p. 61 and the complete removal of the carbon 
dioxide is accomplished by passing the gas mixture into the 
pipette, allowing it to remain there for a moment and then draw- 
ing it back into the burette. If water is being used as the con- 



298 GAS ANALYSIS 

fining liquid in the burette, it is allowed to run down for one 
minute and the residual gas volume is then read off, the diminu- 
tion in volume being equal to the per cent of carbon dioxide in 
the flue gas. For the removal of oxygen a pipette containing 
phosphorus (see p. 164), alkaline pyrogallol (see p. 160) or sodium 
hyposulphite (see p. 168) may be employed; the manipula- 
tion described under these various reagents should be carefully 
followed so that the complete removal of all of the oxygen in the 
gas mixture may be insured. In the analysis of flue gas with the 
older or, indeed, with some of the later modifications of the 
Orsat apparatus, oxygen is not entirely removed. Since this gas 
is absorbed by cuprous chloride which is next used for the deter- 
mination of any carbon monoxide that may be present, a diminu- 
tion in volume resulting from the absorption of oxygen by the 
cuprous chloride would naturally be ascribed to carbon monoxide 
in the gas mixture. This is a frequent cause of error in the 
analysis and in the calculations that are based upon it. 

After the oxygen has been absorbed, a double gas pipette con- 
taining ammoniacal cuprous chloride (see p. 232) is connected 
with the burette, the residual gas is passed over into the pipette 
and the absorption of carbon monoxide is effected by gently 
shaking the pipette backward and forward without disconnect- 
ing it during a period of three minutes. There will usually be no 
diminution in volume after this treatment, for flue gas rarely 
contains carbon monoxide. It is true that many analyses show 
an appreciable amount of this constituent in the gases formed 
in combustion, but in the experience of the author, this is due 
in the great majority of cases to the incomplete removal of 
oxygen referred to in the preceding paragraph. 

If the Orsat-Dennis apparatus is employed, the absorption 
pipette next to the burette is filled with a solution of potassium 
hydroxide, the next pipette with a solution of sodium hyposul- 
phite or of alkaline pyrogallol and the third pipette with an 
ammoniacal solution of cuprous chloride. Carbon dioxide, oxy- 
gen and carbon monoxide are then absorbed by the three 



FLUE GAS ANALYSIS 299 

reagents in the order given. The manipulation of the apparatus 
is described on p. 87. 

Any sulphur dioxide that is present in the flue gas will be 
absorbed by potassium hydroxide in the determination of carbon 
dioxide. If it is desired to determine the amount of sulphur 
dioxide present, a fairly large sample of the gas should be drawn 
directly from the flue through a tube containing a wad of cotton 
to stop the dust, then through a gas washing bottle containing 
a measured volume of a standard iodine solution and finally 
through a gas meter for measurement. Full details of this 
method will be found on p. 274. 

If the plant that is being tested is at a considerable distance 
from the laboratory, it is frequently more convenient to make the 
analysis of flue gas on the spot than to transport the gas sample 
to the laboratory. In such case the portable Hempel apparatus 
described on p. 69 or the Orsat-Dennis apparatus may be 
employed with equally good results. 

Automatic Flue Gas Analysis. The character and com- 
pleteness of the combustion in a furnace or other heating appa- 
ratus may, to a considerable degree, be judged by the percentage 
of carbon dioxide in the gases escaping through the flue. This 
fact has led to the invention of a number of devices for automat- 
ically and continuously determining carbon dioxide. 

Some of these instruments, those that are based upon the 
determination of the specific gravity of the flue gas, render it 
possible to read off the per cent of carbon dioxide at any time, 
but do not record the results. The gas balance of Lux, the 
dasymeter of Siegert and Diirr and the econometer of Arndt are 
instruments of this type. It is reported that they are no longer 
used in practice. The apparatus of Krell-Schultze which is 
based on this principle has met with favor in certain quarters. 

The Carbon Dioxide Recorder. Another form of appara- 
tus is that in which carbon dioxide in the flue gas is absorbed, 
and the gas volume after the absorption is automatically re- 
corded. As an example of instruments of this form the Pre- 



300 



GAS ANALYSIS 




FIG. 89 

cision Simmance-Abady carbon dioxide recorder is here de- 
scribed. A diagram of the apparatus is shown in Fig. 89. a is 



FLUE GAS ANALYSIS '301 

the siphon tank that contains the float b; dd is the extractor 
tank and bell; j[/ is the recorder tank with counterbalanced bell. 
A small stream of water flows in constantly through x and 
enters the reservoir k which is provided with an overflow pipe oo. 
The water flows from the reservoir k into the siphon tank a 
through the hollow valve stem e. As the water enters a the 
float b is raised, and the bell d, which is connected with b by 
means of the chain cc, falls. When the float b rises to the top 
of the siphon tank it strikes the valve stem e, trips the valve 
and momentarily flushes the siphon tank, the water flowing out 
of a through the tube g. This causes the weighted float b to fall ; 
as it does so it lifts the extractor bell d and thus draws into d 
through the pipe p and the three-way cock h a sample of flue gas. 

The water that passes through the siphon tube g falls into the 
small pan below g which then drops, thereby raising the counter- 
weight q and closing the valve h. This pan is automatically 
emptied in time to allow the valve h to open again after the 
proper interval. 

In the meantime water has been flowing into the siphon tank 
a thus raising the float b and lowering the extractor bell d. As 
the bell sinks, the flue gas that it contains is gradually brought 
under pressure and is forced down through the pipe that con- 
nects with d, and through a solution of potassium hydroxide 
contained in the reservoir m. The carbon dioxide in the flue gas 
is here absorbed and the residual gas passes upward into the 
recorder tankj and raises the bell in that tank. Attached to the 
side of this bell j is a scale n that is graduated from 100 % at the 
bottom to zero per cent at the top. The capacity of the bell of 
the extractor tank d is so chosen that when air that is practically 
free from carbon dioxide is passed through the apparatus, the 
recorder bell j rises to the zero point on the scale. When flue 
gas is passed through the apparatus, the same volume of gas is 
collected in the bell d, but on passage through the solution of 
potassium hydroxide the carbon dioxide in this mixture is 
absorbed, with a consequent reduction in the volume of the gas 



302 



GAS ANALYSIS 



escaping into j. The height to which j rises, and consequently 
the percentage of carbon dioxide in the gas mixture is auto- 
matically recorded. The gas in j is then discharged into the 
outer air and the fresh sample of gas passes into it from m. 

To insure constant 
flow of fresh flue gas 
into the apparatus, the 
inlet water tube at x is 
caused to act as an in- 
jector or aspirator, and 
is connected with p by 
a branch pipe that rises 
and is joined to the as- 
pirator by the side arm 
pi. This serves to con- 
tinuously exhaust the 
pipes that connect the 
recorder to the boilers, 
which insures that the 
successive samples of 
gas that are analyzed 
are from the boiler flue 
and are not stagnant 
gases from the con- 
necting pipes. Fig. 90 
shows this recorder 
mounted and ready for 
use. 

The Autolysator. - 
Instruments of the 
FIG. 90 above type are open 

to the objection that 

the analyses are separated by intervals of several minutes, 
which renders it impossible to read the carbon dioxide con- 
tent of the flue gas at any desired moment. This difficulty is 




FLUE GAS ANALYSIS 



303 



overcome by such an apparatus as the Autolysator of Strache, 
Johoda and Genzken. 1 .. 

This instrument renders it possible to read off, at any moment, 
the per cent of carbon dioxide then present in the flue gas, and 
it also furnishes a continuous record of the percentage of this 
gas. The essential parts of the device are shown in Fig. 91. K 
is a capillary tube the ends of which communicate with the 
differential manometer M . One end of K is connected with the 
regulating valve A which in turn is joined to a water suction 
pump. 




FIG. 91 

The passage of the gas through the capillary K is dependent 
upon the difference in pressure shown upon the manometer M . 
If the volume of gas is kept constant by.a proper adjustment of 
the valve A the volume of gas passing through K is also constant. 
The specific gravity of the gas has no influence upon the speed 
of flow through the long capillary tube. The constant volume 
of gas passing through K is drawn through a second capillary / 
the two ends of which are joined to the manometer N. 

Between the two capillary tubes are introduced the absorp- 
tion vessels B and C which serve to free the gas that is passed 

1 Z. /. chemische Apparatenkunde, 2 (1907), 57. 



304 GAS ANALYSIS 

through J from the constituent that is to be determined. 
The gas mixture under examination enters the apparatus 
at D. 

It is apparent that if no gas is absorbed when the mixture 
passes through B and C the same amount of gas will pass through 
the capillary / in a unit of time as flows through the capillary K. 
If the two capillaries are exactly the same diameter and length, 
the difference in pressure in TV will be exactly the same as that 
shown by M. If, on the other hand, the absorption vessels B 
and C remove a constituent of the gas mixture, then a larger 
volume of gas must pass through the capillary / in a unit of 
time than through the capillary K. If, now, with the aid of the 
regulating valve A the reading of the manometer M and conse- 
quently the gas volume flowing through K be kept constant, 
the amount of gas that will pass through / will increase in 
proportion to the percentage of absorbable constituents that it 
contains. This will increase the difference in level of the liquid 
in the two arms of the manometer N and this difference shows 
directly the percentage of the absorbed constituent in the gas 
mixture. By means of an empirical scale attached to N the 
percentage in the gas mixture of the gas that is being absorbed 
in B and C may be read off at any moment. The apparatus is 
further provided with an automatic registering device which 
gives a continuous record of the percentage of absorbed gas. 
This form of autolysator is manufactured by the Vereinigte 
Fabriken fur Laboratoriumsbedarf, Berlin. 

The Gas Refractometer. Another interesting instrument 
for the determination of a constituent gas in a mixture of gases 
is the Gas Refractometer designed by Haber. 1 The method is 
based upon the fact, first ascertained by Dulong, 2 that the 
light-refraction of gases may be determined with exactness by 
means of a gas prism and telescope; and upon the law of Biot and 

1 Vortrag auf der Hauptversammlung des Vereins deutscher Chemiker, Nurnberg, 
June 8, 1906. Also in Zeit.f. angew. Chem., 19 (1906), 1418. 

2 Ann. de chim. et de phys., 31 (1826), 154. 



FLUE GAS ANALYSIS 305 

Arago 1 that the light-refraction of a gas mixture may be cal- 
culated in simple manner from the refraction of the several 
constituents and their partial pressures. 

In other words, if the index of refraction, less one, is termed 
the refractive power, the total refractive power of a gas mixture 
is equal to the sum of the refractive powers of the constituent 
gases in the same manner as the total pressure of a gas mixture 
is equal to the sum of the partial pressures of the several gases 
that are present. 

To determine the percentage of a gas in a mixture with the 
aid of the gas refractometer, the refraction of the mixture is 
first measured, and then the refraction of the residue after the 
removal of the constituent in question. Or if it is desired to 
ascertain the amount of a gas that has been added to a mixture, 
as in the carburetting of illuminating gas, the refraction before 
and after the addition of the gas is measured. 

The refractometer has been successfully employed in the 
solution of certain special problems in technical practice. It is 
manufactured by the firm Carl Zeiss in Jena, Germany. 

L M em. de I'Acad. de France, 7 (1806), 301. 



CHAPTER XV 

ILLUMINATING GAS FUEL GAS 

COAL GAS PINTSCH GAS WATER GAS PRODUCER GAS 
BLAST-FURNACE GAS NATURAL GAS 

The gas mixtures that fall under the above heading show 
great differences in composition, but they are here grouped 
together because the methods employed for their analysis and 
the sequence of the several determinations are closely similar 
and, in many cases, identical. 

Probably the most complex of these gas mixtures is that 
which results from the destructive distillation of coal, a product 
termed coal gas. A detailed description of the methods em- 
ployed in the examination of this gas is given in the following 
pages, and will be found to include practically all of the points 
involved in the analysis of the other gas mixtures enumerated 
at the head of this chapter. 

COAL GAS 

Although the quantitative composition of coal gas varies with 
the methods employed in its manufacture and with the nature 
of the coal, the constituents of the product are nearly the same 
in every case. The washed gas contains carbon dioxide, carbon 
monoxide, hydrogen, methane, heavy hydrocarbons (illumi- 
nants), vapors of other hydrocarbons such as benzene and 
naphthalene, gaseous compounds of sulphur, water vapor, ni- 
trogen, oxygen, and sometimes cyanogen or hydrogen cyanide. 
The unwashed gas contains ammonia and uncondensed tar, in 
addition to the above ingredients. 

The complete examination of coal gas comprises: 
i. The determination of the illuminating power of the gas; 

306 



ILLUMINATING GAS FUEL GAS 307 

2. The determination of the specific gravity of the gas; 

3. The gas volumetric determination of the principal con- 
stituents of the gas mixture; 

4. The determination of naphthalene; 

5. The determination of the total sulphur in the gas; 

6. The determination of the total cyanogen in the gas; 

7. The determination of the heating value of the gas (see 
Chapter XVI). 

i. The Determination of the Illuminating Power of Coal Gas 

In the measurement of the intensity of sources of light two 
general methods are employed, the direct-comparison method 
and the substitution method. In the first, the light whose 
intensity is to be measured is placed on one side of the photo- 
metric apparatus and the standard light on the other side and 
the two are directly compared. In the second, a light of con- 
venient intensity is compared with the standard; the standard 
is then removed and the light whose intensity is to be compared 
is then put in its place. The intensity of the last light in the 
terms of the standard is then computed. 

While the substitution method is in general superior to that 
of direct comparison the latter is usually employed in the in- 
dustrial measurement of the illuminating power of gases. 

The most satisfactory primary standards are the sperm 
candle, the pentane lamp, the Hefner amylacetate lamp and the 
carbon-filament incandescent lamp. 1 Many forms of photom- 
eter have been devised. Full details concerning their construc- 
tion and use may be found in Praktische Photometric by Dr. 
Emil Liebenthal (1907) and in Photometric Units and Standards 
by E. B. Rosa (see note). 

Of the direct comparison instruments, that designed by Bunsen 
is widely used and gives quite satisfactory results. The instru- 

1 A discussion of these standards will be found in the lecture of Rosa upon pho- 
tometric units and standards published in Lectures on Illuminating Engineering, The 
Johns Hopkins Press, 1911. 



308 GAS ANALYSIS 

ment is constructed on the following principle. If a spot upon 
a screen of white paper is rendered translucent by pressing 
grease or wax into the paper, and the screen is then held between 
two sources of light, the grease spot will appear darker than the 
surrounding paper when the screen is viewed from the side on 
which the stronger light falls. If the illumination on the further 
side of the paper is the stronger, the spot will appear to the eye 
to be lighter than the rest of the screen. If the screen is moved 
to such position between the two sources of light that the in- 
tensity of light falling upon each side of it is the same, the spot 
will disappear. The distance from the screen to each of the two 
lights is now measured. Since the intensities of the two flames 
are to each other as the squares of the distances of the flames 
from the screen, the candle power of one flame in terms of the 
other may be computed according to the formula 



in which 7 is the candle power of the light of known intensity 



mi 

LWJ 



o 
FIG. 92 

and d the distance of this light from the screen, and /' is the 
candle power of the light being measured and d' its distance from 
the screen. 

The construction of the Bunsen photometer is shown in 
Fig. 92. 

LI and L 2 are the two sources of light under comparison and 



ILLUMINATING GAS FUEL GAS 309 

5* the screen of paper on which is the grease spot. To enable the 
operator to see both sides of the screen simultaneously, the 
Riidorff mirrors M \ and MI, each placed at an angle of 70 with 
the plane of the screen, are almost universally employed. Upon 
looking through the opening the eye sees the two images of 
the disk. 

In determining the intensity of a source of light Z, 2 , in terms of 
LI, the photometer screen is moved to the right or left until the 
contrast between the greased and ungreased portions of the 
screen is the same on one side as on the other. The distances 
from the screen to the two sources of light are then read off, 
and the intensity of Lz computed by means of the formula given 
above. 

2. The Determination of the Specific Gravity of Coal Gas 

The specific gravity of coal gas is usually determined by meas- 
uring its time of escape through a small opening. Methods 
that may be employed for this purpose are described on p. 44. 

j. The Gas-Volumetric Analysis of Coal Gas 

The volumetric analysis of coal gas comprises the determina- 
tion of such constituents as are present in amounts sufficient to 
permit of their accurate determination in a sample of not more 
than 100 cubic centimeters. 

These gases usually are: 

1. Carbon dioxide, 

2. Benzene, 

3. Other heavy hydrocarbons, chiefly ethylene, 

4. Oxygen, 

5. Carbon monoxide, 

6. Hydrogen, 

7. Methane (and sometimes ethane), 

8. Nitrogen. 

Inasmuch as methods for the determination of these various 
gases have already been described in Chapter XIII, there will 



310 GAS ANALYSIS 

here be given only a description of the successive steps em- 
ployed in a complete volumetric analysis of coal gas, together 
with such details of the manipulation as have not previously 
been discussed. 

The Determination of the Absorbable Gases. Appara- 
tus. In the opinion of the author, the best form of apparatus 
for the rapid and accurate determination of the absorbable con- 
stituents of coal gas, numbers i to 5 inclusive in the above list, 
is that of Hempel. The Orsat-Dennis apparatus gives equally 
good results, but if constructed with the six absorption pipettes 
that are needed for the removal of the five absorbable gases, it 
becomes so unwieldy that it cannot be recommended for this 
purpose. 

For usual technical practice, a Hempel gas burette without 
water jacket may be employed, although somewhat more ac- 
curate results can be obtained with the use of a water mantle 
around the burette. If the room in which the analysis is carried 
on undergoes fluctuations of temperature, a water-jacketed 
burette should be used in all cases. The accuracy of the analysis 
is of course increased by the use of mercury as the confining 
liquid in the burette, but the differences between the results 
obtained over mercury and over water are usually not great 
enough to warrant the employment of mercury in technical 
practice. 

Manipulation. Clean the burette and level- tube (Fig. 33) 
and see that the rubber tube on the upper end of the burette is 
in good condition and is securely fastened in place by the wire 
ligature. Place an amount of water sufficient for the filling of 
the burette and level-tube in a flask, and saturate it with the 
coal gas that is to be analyzed (see p. 59). Fill the burette 
and level-tube with this water in the manner described on 

P- 59- 

Connect a glass tube to the gasometer or pipe containing the 
coal gas by means of a short piece of rubber tubing. Pass the 
gas through this tube until all air has been expelled, insert the 



ILLUMINATING GAS FUEL GAS 311 

end of it into the rubber tube at the top of the burette, and draw 
into the burette somewhat more than 100 cc. of the gas. Close 
the pinchcock at the top of the burette, disconnect the glass tube, 
and after the water in the burette has run down for one minute 
measure off a sample of exactly 100 cc. at atmospheric pressure 
in the manner described on p. 59. Verify the accuracy of 
this measurement by bringing the water levels in the burette 
and level-tube to the same height and noting whether the 
meniscus in the burette stands exactly at the 100 cc. mark. 

Carbon Dioxide. Place a wooden pipette stand at the side 
of the burette, and, upon the stand, a Hempel gas pipette for 
the absorption of carbon dioxide (p. 225). Connect the pipette 
with the burette by either of the procedures described on 
pp. 6 1 and 64. Where a number of analyses are to be made 
one after another, the second method of connecting the pipettes 
with the burette, described on p. 64, in which a pinchcock is placed 
upon the rubber tube of the pipette, and the solution in the 
pipette is driven over to the far bend of the connecting capillary 
tube and is held there by closing the pinchcock on the pipette, 
will be found to add much to the convenience of the manipu- 
lation and to the rapidity of the analysis. Employ this ma- 
nipulation in connecting other pipettes with the burette unless 
there is a reason for not driving the reagent up into the con- 
necting capillary tube, which is the case with fuming sulphuric 
acid. 

Open the pinchcock at the top of the burette, and pass the 
gas sample into the pipette, allowing the water from the burette 
to follow to the first bend of the capillary tube of the pipette. 
After the gas has stood for thirty seconds in the pipette, draw 
it back into the burette by lowering the level-tube, and bring 
the solution of potassium hydroxide to the same point in the 
connecting capillary at which it stood when the pipette and 
burette were first connected. Disconnect the pipette, allow the 
water in the burette to run down for one minute, bring the sur- 
face of the water in the level-tube to the same height as that in 



312 GAS ANALYSIS 

the burette and read the volume of the residual gas. The dim- 
inution in volume measured in cubic centimeters gives directly 
the percentage of carbon dioxide in the coal gas. 

Benzene. Replace the potassium hydroxide pipette by a 
double pipette for solid reagents (p. 58) that is charged with a 
solution of ammonia nickel cyanide (p. 256). Connect the bu- 
rette with this pipette in the manner employed above and pass 
the gas repeatedly back and forth between the burette and 
pipette for a period of three minutes. Pass the gas into the 
burette, close the pinchcock at the top of the burette, and re- 
place the pipette containing ammonia nickel cyanide by a 
double pipette for solid reagents that is charged with a five per 
cent solution of sulphuric acid (p. 257). Pass the gas back and 
forth about two minutes to remove ammonia. 1 Then draw the 
gas into the burette, close the pinchcock, allow the water in the 
burette to run down for one minute as usual, and read the 
volume of the gas. The difference between this volume and that 
remaining after the absorption of the carbon dioxide, measured 
in cubic centimeters, gives the percentage of benzene in the 
gas. 

Other Heavy Hydrocarbons. Connect the burette by 
means of a dry capillary tube with a pipette containing fuming 
sulphuric acid, making the connection and effecting the absorp- 
tion in the manner described on p. 247. 

Draw the gas back into the burette to such point that the acid 
stands at the original height in the capillary tube of the pipette. 
Close the pinchcock at the top of the burette, replace the sul- 
phuric acid pipette by one containing potassium hydroxide, and 
pass the gas into this pipette to remove sulphur trioxide and sul- 
phur dioxide. Drive the acid back into the burette, and measure 
the decrease in volume after the water has run down for the 

1 If mercury is used in the burette the small amount of water that usually covers 
its surface will absorb a considerable quantity of ammonia from the reagent. In 
such case a volume of dilute sulphuric acid amply sufficient to neutralize the am- 
monium hydroxide thus formed should be drawn over from the pipette into the bu- 
rette, and then driven back into the pipette. 



ILLUMINATING GAS FUEL GAS 313 

usual one minute. The difference between this and the last 
reading gives the percentage of heavy hydrocarbons other than 
benzene. 

Oxygen. Connect the burette with the pipette contain- 
ing phosphorus or alkaline pyrogallol or sodium hyposulphite, 
and remove the oxygen in the manner described in Chapter XIII 
for the reagent that is employed. The diminution in volume 
resulting from this absorption gives the percentage of oxygen in 
the gas. 

Carbon Monoxide. Join the burette to a Hempel double 
pipette containing ammoniacal or acid cuprous chloride (see 
p. 232), drive the gas over into the pipette, and hasten the ab- 
sorption of the carbon monoxide by gently rocking the pipette 
backwards and forwards for three minutes without disconnect- 
ing it from the burette (see p. 63). Draw the gas back into 
the burette, close the pinchcock of the burette, and replace the 
pipette with another pipette containing a solution of cuprous 
chloride that has been but slightly used. Repeat the manipula- 
tion and after two minutes shaking pass the gas back into the 
burette. Some ammonia or hydrogen chloride from the reagent 
will now be present in the gas mixture. When water is used as 
the confining liquid in the burette, these gases will be absorbed 
by it. But when mercury is employed as the confining liquid 
they should be removed before the gas is measured, the ammonia 
by passing the gas into a pipette containing 5% sulphuric acid, 
the hydrogen chloride by passing the gas into a pipette con- 
taining potassium hydroxide. Measure the residual volume. 
The diminution in volume gives the per Cent of carbon monoxide 
in the gas. 

Disconnect the cuprous chloride pipette and replace it by a 
simple pipette (Fig. 34) containing water, and pass the gas 
residue from the burette into this pipette, allowing the water 
from the burette to follow over to the lower bend in the long 
capillary tube of the pipette. Pour out the water in the burette 
and level-tube, rinse out the tubes first with dilute hydrochloric 



314 GAS ANALYSIS 

acid and then with distilled water, and fill them with distilled 
water. Pass the gas back again into the burette and measure its 
volume. 

If hydrogen, methane, and nitrogen are to be simultaneously 
determined in the combustion pipette (see below), the gas residue 
may be passed directly into this pipette after the determination 
of carbon monoxide. The burette that is used in the combus- 
tion is filled with mercury, not with water. 

Hydrogen, Methane (and Ethane), and Nitrogen. 
These gases may be determined separately by the successive 
removal of hydrogen and the paraffins, or if methane is the only 
hydrocarbon present they may be determined simultaneously 
by a single explosion or combustion. If ethane is present with 
methane, the amounts of the two hydrocarbons cannot be deter- 
mined by combustion unless the hydrogen is first removed (see 
Chapter XI). 

For the simultaneous determination of hydrogen, methane 
and nitrogen, and of methane, ethane and nitrogen the combus- 
tion method of Dennis and Hopkins is to be preferred to the 
explosion of the residue with air or oxygen because in the former 
procedure the possibility of incomplete combustion or of the 
formation of measurable amounts of oxides of nitrogen is 
avoided, and because further the complete oxidation of the com- 
bustible gases is independent of the composition of the gas mix- 
ture. The manipulation of the combustion pipette for the simul- 
taneous determination of hydrogen, methane and nitrogen, and 
the calculation of the analytical results is described in detail on 
pp. 149 and 244. If both methane and ethane are present with 
hydrogen and nitrogen in the residue remaining after the removal 
of the absorbable gases, the hydrogen is first removed, and the 
methane and ethane are then burned in the combustion pipette, 
the total contraction being noted, and the volume of carbon 
dioxide formed being ascertained. 

The percentages of methane and ethane are then calculated 
by means of equations 7 and 8 on p. 130. 



ILLUMINATING GAS FUEL GAS 315 

If x represents methane and y ethane, then 

C0 2 = CH 4 + 2 C 2 H 6 , (7) 

and 

T.C. =2 CH 4 + 2^C 2 H 6 (8) 

Subtracting the second equation from twice the first 
2 CO 2 T. C. - ijC 2 H 6 or 



C2 H 6 



3 
Then, knowing the volume of ethane, 

CH 4 = C0 2 2 C 2 H 6 

The successive determination of hydrogen, methane (and 
ethane) and nitrogen may be accomplished in a variety of ways; 
the hydrogen is first removed, the hydrocarbons are then 
burned, and the nitrogen is calculated by difference. 

Of the many methods for the removal and determination of 
hydrogen, the most convenient and accurate are the absorption 
with palladium black (see p. 188), and the fractional combus- 
tion with copper oxide (see p. 201). The fractional combus- 
tion with palladium asbestos cannot be recommended for the 
reasons set forth on p. 193 to 196.' The Hempel method of 
fractional combustion with palladium black (see p. 196) re- 
moves hydrogen completely, but it is open to the objection that 
only a small portion of the combustible residue is used, with 
consequent multiplication of any error that may be made in the 
measurements. 

If the hydrogen is to be removed by absorption with palladium 
black, the gas burette containing the gas residue is connected 
with the U-tube containing the palladium black, the amount 
of air in this U-tube having previously been ascertained by the 
method described on p. 190. The hydrogen is then absorbed 
(see p. 189), and the residual gas is drawn back into the 
burette and measured. The diminution in volume is equal to 



316 GAS ANALYSIS 

the hydrogen in the gas residue plus the oxygen in the air that 
was originally inclosed in the U-tube when the apparatus was 
put together. Subtracting this volume of oxygen from the total 
contraction gives the hydrogen in the gas. 

If the hydrogen is to be removed by fractional combustion 
with copper oxide, the apparatus and method described on 
pp. 201 to 206 is employed. 

After hydrogen has been determined either by absorption 
with palladium black or by fractional combustion with copper 
oxide, the tubes used in these methods will still contain some 
of the combustible residue which must be swept over into the 
burette with about 30 cc. of nitrogen gas from a phosphorus 
pipette before the combustion of the hydrocarbons is proceeded 
with. It is not necessary to know the volume of nitrogen that 
is hereby added to the gas residue, but the total volume of the 
residue and the nitrogen that has been added to it must be ascer- 
tained by measurement before the combustion is made. 

After the removal of the hydrogen, the determination of the 
hydrocarbons of the paraffin series is next made. If methane 
is the only hydrocarbon present, the combustion may be carried 
out in a combustion pipette filled with water because it is here 
not necessary to determine the volume of carbon dioxide that 
is formed in the combustion. If, however, the residue con- 
tains both methane and ethane, the gas burette and the com- 
bustion pipette should be filled with mercury because both 
the total contraction and the volume of carbon dioxide formed 
must be ascertained (see p. 315). If methane is the only hydro- 
carbon present the combustion is carried out as follows: 

About 100 cc. of oxygen or of air, if that volume of air con- 
tains enough oxygen to insure complete combustion, is run into 
the combustion pipette, which is then joined to the burette con- 
taining the gas residue. The terminals of the pipette are then 
connected w r ith the source of current, the current is turned on, 
and the spiral heated to dull redness. The gas residue is slowly 
passed into the pipette, the current being regulated so that the 



ILLUMINATING GAS FUEL GAS 317 

spiral will not rise above a dull red heat at any time. When all 
of the gas has been passed over into the pipette, the platinum 
spiral is kept at dull redness for 60 seconds. The current is then 
turned off, the pipette is allowed to cool, and the residual gas is 
passed back into the burette. Without measuring the residual 
gas volume at this point, the combustion pipette is detached, 
and a gas pipette containing potassium hydroxide is connected 
with the burette. The gas is passed over into this pipette to 
remove all carbon dioxide and is drawn back into the burette 
and measured. When methane is burned, one volume of the gas 
unites with two volumes of oxygen to form one volume of carbon 
dioxide and two molecules of water. If the carbon dioxide re- 
sulting from the combustion is absorbed, the diminution in 
volume that results from the combustion of one volume of 
methane equals three times the volume of the gas. 

CH 4 -f 2 O 2 = C0 2 + 2 H 2 O 
i vol. 2 vols. absorbed liquid 

Consequently one-third of the total diminution observed in this 
combustion equals the volume of methane that is present in the 
gas residue. 

If the residue contains both methane and ethane, the combus- 
tion is carried out over mercury, the contraction in volume after 
the combustion is measured, and the volume of carbon dioxide 
that has been formed is determined by absorption with potas- 
sium hydroxide. The percentage of each of the gases is then 
calculated by the method given on p. 315. 

Nitrogen. It has hitherto been customary in the analysis 
of coal gas to state that the amount of nitrogen in the gas is 
equal to the final residual gas volume after the removal of the 
absorbable constituents and the combustible gases. Usually, 
however, small amounts of air are left in the connecting capil- 
lary tube when the burette and pipettes are joined together, 
and these minute air volumes will cause errors that, although 
negligible in the separate determinations, have a cumulative 



3i8 GAS ANALYSIS 

effect of considerable magnitude upon the volume of residual 
nitrogen. For this reason it is preferable to determine nitrogen 
in a separate sample of the gas. 

This may be done by burning a sample of the gas with an ex- 
cess of oxygen, removing the products of combustion by means 
of potassium hydroxide, absorbing the excess of oxygen with an 
alkaline solution of pyrogallol, and measuring the residue, 
which should be pure nitrogen. The method is carried out as 
follows: 

100 cc. of pure oxygen free from combustible gases, and con- 
taining either no nitrogen, or nitrogen of known amount, is 
placed in the combustion pipette, and a measured amount of the 
sample of illuminating gas, about 50 cc., is passed from a Hempel 
burette into the combustion pipette in the usual manner. After 
combustion is complete the residue is returned to the burette, 
and carbon dioxide and the excess of oxygen are removed by 
passing the gas residue successively into a pipette containing 
potassium hydroxide and one containing alkaline pyrogallol. 
The residual gas is nitrogen. Since a sample of coal gas less than 
100 cc. is used in this determination, the per cent of nitrogen 
in the gas is not equal to the residual volume, but to 

residual volume X 100 
volume of sample 

4. The Determination of Naphthalene in Coal Gas 



Naphthalene is best determined by absorption in picric acid 
according to the method described on p. 261. Before the gas 
enters the absorbent, however, it should be freed from tar, 
cyanogen, hydrogen sulphide and ammonia. This may be 
accomplished 1 by passing the gas mixture through three wash 
bottles containing dilute sulphuric acid and then through two 
wash bottles containing a solution of potassium hydroxide (the 
authors do not give the strength of these reagents), the five 

1 Albrecht and Muller, /./. Gasbeleuchtung, 54 (1911), 592. 



ILLUMINATING GAS FUEL GAS 319 

wash bottles being connected glass to glass by short pieces of 
rubber tubing and being placed in a drying oven heated to 
about 50. From the last washing bottle the gas passes through 
two wash bottles containing picric acid, these bottles being out- 
side of the oven and being connected at their further end with a 
gas meter and suction pump. 

5. The Determination of Total Sulphur in Coal Gas 

Illuminating gas that is prepared by the dry distillation of 
coal always contains compounds of sulphur such as hydrogen 
sulphide and carbon disulphide. Although the greater part of 
these products is removed in the purification of the gas before it 
is admitted to the mains, some of the compounds are always 
found in the washed gas. These sulphur compounds are ob- 
jectionable because of the sulphur dioxide that results from 
their combustion. Inasmuch as all of them form sulphur 
dioxide when they are burned, the determination of the total 
sulphur in the gas is customarily required, and usually no 
attempt is made to determine the separate compounds of the 
element that are present. 

The method that is most generally employed for the deter- 
mination of the total sulphur in illuminating gas consists in 
burning the gas with the aid of oxygen or air, converting the 
resulting sulphur dioxide to sulphuric acid, and determining 
that final product by gravimetric or volumetric means. 1 

The two forms of apparatus most generally used for this 
determination are that proposed by Drehschmidt 2 and the 
English "Referees' Test." 3 The original apparatus of Dreh- 

1 Among the many articles upon this subject there may be cited the following: 
Briigelmann, Z. /. anal. Chem., 15 (1876), 175; Knublauch, Z. f. anal. Chem., 21 

(1882), 335; Poleck, Z./. anal. Chem., 22 (1883), 171; Fairley, /. Soc. Chem. Ind., 5 
(1886), 283; Drehschmidt, Chem. Zeitung, n (1887), 1382; Hempel, Gasanalytische 
Methoden, 3d ed., 1900, p. 255; Witzeck, J. Gasbelewhtung, 46 (1903), 21; Harding, 
/. Am. Chem. Soc., 28 (1906), 537. 

2 Loc. cit. 

3 Abady, Gas Analysts' Manual, p. 178. 



320 



GAS ANALYSIS 



schmidt is fragile and costly, and because of these characteristics 
it is inferior to the modification that has been designed by Hem- 
pel and that is shown in Fig. 93. 




FIG. 93 

Determination of Sulphur by Drehschmidt-Hempel 
Method. The illuminating gas under examination is measured 
in an experimental gas-meter and then passes through a short 
piece of rubber tubing b and the glass tubing c into the flask A , 
Fig. 93. b is provided with a screw pinchcock. The tube c is 
of hard glass, is about 5 mm. in diameter, is bent somewhat 



ILLUMINATING GAS FUEL GAS 321 

downward after it enters the flask and is drawn out at the end to 
a small opening. The neck of the receiving flask A is drawn 
down in the flame of the blast lamp to a small tube which is 
connected at d by means of a piece of rubber tubing with the 
absorption apparatus DD. The three-way glass tube e is in- 
serted in the tubulure of the flask and is held in position in the 
neck by a piece of rubber tubing or a rubber stopper with a large 
opening. The side arm of the three-way piece e is joined by the 
rubber tube / to the cylinder B. This cylinder is filled with 
pieces of pumice-stone upon which there is allowed to drop a 
solution of potassium hydroxide from a separatory funnel. The 
air drawn into the apparatus must pass through this tower and 
is there freed from any hydrogen sulphide which may be present 
in the air of the laboratory, g is connected with an ordinary 
water suction pump. 

In each absorption bottle DD is placed 20 cc. of a 5 per cent 
solution of potassium carbonate. To the contents of the first 
two bottles there is added a few drops of bromine to oxidize the 
sulphur dioxide to sulphuric acid. 

The illuminating gas should be allowed to pass through the 
gas-meter for some time previous to the beginning of the deter- 
mination, to make sure that the meter is completely filled with 
the gas under examination. 

When the apparatus has thus been prepared for the deter- 
mination, the water suction pump is started, and a rapid current 
is drawn through the purifying cylinder B, the flask A, and the 
bottles DD. The tube c is withdrawn from the flask, and the 
gas is ignited at its outlet. The screw pirichcock b is closed until 
the flame is about i cm. long, and c is then introduced into A 
and the cork h is firmly inserted into position, c should be 
moved in or out through h until the flame burns in the middle of 
the flask. It should lie slightly below the lower side of the 
tubulure of the flask. In this position the flame will burn 
quietly for hours, but if it is above the tubulure it will go out, 
because in the upper part of the flask the products of combustion 



322 GAS ANALYSIS 

are not removed with sufficient rapidity by the entering current 
of air. By means of the screw pinchcock b it is easy so to regulate 
the flame as to cause it to burn with sharply denned edges, thus 
insuring complete combustion of the illuminating gas. Note the 
temperature of the gas, the prevailing barometric pressure, and 
the reading of the manometer on the meter. 

After about fifty liters of the gas has been burned, read the 
meter accurately and remove the burner from the globe. At 
this point the barometer, the manometer on the meter, and the 
thermometer should be read again and the average value should 
in each case be used in the calculation of results. 

Rinse the globe with distilled water into a beaker. Pour the 
contents of the three (Muencke) wash bottles into the beaker 
and rinse well with distilled water. Acidify the solution with 
hydrochloric acid and heat to boiling in order to expel the bro- 
mine. Add barium chloride to the hot solution and determine 
the weight of barium sulphate in the usual manner. 

The sulphur, which may exist in the gas as hydrogen sulphide, 
as carbon disulphide, or as organic sulphur compounds, is 
burned to sulphur dioxide, 862, which is oxidized by the bro- 
mine to sulphur trioxide, SO 3 , and this reacts with the po- 
tassium carbonate to form potassium sulphate. Hydrochloric 
acid is added to the solution to decompose the carbonate 
present. 

The amount of sulphur in the gas is calculated from the 
weight of the barium sulphate found, the result being expressed 
in terms of grams of sulphur per cubic meter (1000 liters) of the 
gas at o and 760 mm. 
Grams sulphur per cubic meter = 

1000 , At. wt. sulphur 760 (i + 0.00^67^) 

xx (~p p \ r <, 2 v ' '. 

V J Mol. wt. BaSO 4 (B + b) m 

In the above 

V = liters of gas burned, 
P = grams BaSO 4 found, 



ILLUMINATING GAS FUEL GAS 323 

Pi = grams BaSC>4 found in blank test of reagents, 1 
B = observed barometric pressure, 

b = pressure (in addition to atmospheric) of gas in meter, 
t = temperature of gas in meter, 
m = tension aqueous vapor at P. 
At. wt. S 

AT i + P cr> = ai 3732S- 
Mol. wt. BaSO 4 

To express results as "grains sulphur per 100 cubic feet of 
the gas," multiply "grams per cubic meter" by the factor 
43.698. 

Schumacher and Feder 2 state that only sulphur dioxide and 
no sulphur trioxide is formed in the combustion of the gas in 
the Drehschmidt apparatus. Upon this observation they base 
a volumetric method for the determination of total sulphur. 

A measured volume of a solution of potassium iodate of known 
strength, that contains about 18 grams of potassium iodate to 
the liter, is placed in the absorption bottles DD, and the gaseous 
products of the combustion are drawn through this liquid in the 
usual manner. The solution is then transferred to a flask and 
is boiled for from ten to fifteen minutes to expel the liberated 
iodine. The liquid is then cooled, a little sulphuric acid is 
added, and the excess of potassium iodate is titrated with 
sodium thiosulphate. The authors state that the results agree 
quite satisfactorily with those obtained by the gravimetric 
method. 

In the use of the Hempel modification of the Drehschmidt 
apparatus difficulty is at times experienced in so regulating the 
combustion in the flask A that the flame will be non-luminous 
and at the same time will burn continuously throughout the 
run. Harding states 3 that this difficulty may be avoided by the 

1 The bromine water and potassium carbonate used should be tested qualitatively 
for the presence of sulphates. If the test gives positive results the sulphur is deter- 
mined in a quantity of these reagents equal to that used in the experiment. 

2 Z. /. Unters. Nahr.-Genussm., 10 (1005), 649. 

3 /. Am. Chem. Soc., 28 (1906), 537. 



324 GAS ANALYSIS 

use of a special burner of hard glass which is figured and de- 
scribed in his article. 

Determination of Sulphur by Referees' Method. The of- 
ficial method in use in London, England, for the determination 
of the total sulphur in illuminating gas is known as the Referees' 
Test. 1 

In this method the gas is burned in air that contains ammonia, 
and the resulting water, ammonium carbonate, ammonium 
sulphite, and ammonium sulphate are collected in a condensing 
tower. The products of combustion are then dissolved in water, 
the solution is acidified with hydrochloric acid and is boiled 
to expel carbon dioxide. The sulphate that is present is then 
precipitated with a solution of barium chloride. The accuracy 
of the method has been called in question because of the pos- 
sibility of incomplete retention of the oxides of sulphur by 
the condensing tower, and further because of the probability 
that some of the sulphur would be oxidized only to sulphur 
dioxide, 2 in which case the resulting ammonium sulphite would 
be decomposed when the solution is boiled with hydrochloric 
acid and some sulphur would escape precipitation as barium 
sulphate. These points have been investigated in the Cornell 
Laboratory by Mr. George Hopp. He found that the condensing 
tower that is customarily used will retain the oxides of sulphur 
if the rate of flow of the gas does not exceed twenty liters per 
hour. As to the second point, however, his analyses show that 
the Referees' method yields too low results unless the solution 
of the products of combustion is treated, before acidification, 
with an oxidizing agent that will convert the sulphite to sulphate. 
With these modifications the method appears to give quite 
satisfactory results. 

In the Referees' method the gas is burned in a Bunsen burner 
B, Fig. 94, that stands in a perforated metal base D. The burner 

1 A detailed description of this procedure is given in Abady's Gas Analysts' Manual, 
Chapter V. 

2 In this connection see Schumacher and Feder, Zeit. f. Unters. Nahr.-Genussm., 
10 (1905), 649. 



ILLUMINATING GAS FUEL GAS 



325 




FIG. 94 

that is furnished with the apparatus is a small Bunsen burner 
with a steatite tip. With an ordinary Bunsen burner, however, 
the gas can be burned more rapidly, without the formation of a 



326 GAS ANALYSIS 

smoky flame, than is possible with the special burner. The 
products of combustion pass upward through the conical glass 
chimney C. The upper end of the chimney passes through a 
rubber stopper that is inserted into the tubulure of the cylinder 
A. The upper portion of the cylinder is filled with pieces of 
glass rod about 40 mm. long and 8 mm. in diameter, or with 
glass balls about 15 mm. in diameter. In the bottom of the 
cylinder is a round hole into which is inserted a rubber stopper 
that carries a glass tube. The condensed water flows through 
this tube into the beaker E. 

Pieces of non-effloresced ammonium sesquicarbonate, 

((NH 4 ) 2 CO 3 - 2 NH 4 HCO 3 ), 

about 40 grams in all, are placed around the burner on a per- 
forated plate in the base D. A few pieces of the salt are also 
placed on top of the glass rods or balls in the cylinder. The 
ammonia that is set free by the spontaneous decomposition 
of this substance unites with the sulphur dioxide and prevents 
its escape. 

The gas is first passed through a gas meter until all air has 
been driven from the meter and the water in the meter is sat- 
urated with the gas under examination. The meter is then 
connected with the burner B and the gas is lighted at the burner. 
The flame is turned down until the rate of consumption of gas 
is not more than 20 liters per hour. A screw clamp placed upon 
the rubber tube of the burner furnishes a means of accurately 
adjusting the height of the flame. The burner and the base D 
are then placed under the conical glass chimney and the upper 
end of the chimney is at once inserted into the opening of the 
cylinder A. Readings of the meter, the barometric pressure, 
the manometer on the meter and the temperature of the gas 
as it passes through the meter are immediately made. 

When from 50 to 60 liters of gas has been burned, the gas is 
turned off and the instruments that were read at the beginning 
of the run are now read again. The averages of the readings 



ILLUMINATING GAS FUEL GAS 327 

of the barometer, thermometer and manometer are used in the 
calculation of results. The beaker E is replaced by a clean empty 
beaker and the cylinder A is rinsed by pouring through the tube 
attached to the upper opening of the cylinder two or three por- 
tions of distilled water of 25 cc. each. The chimney C is also 
rinsed out with distilled water into the beaker. These rinsings 
are then added to the contents of the first beaker. A measured 
amount, about 2 cc., of saturated bromine water is added 
and the liquid is thoroughly stirred for a few moments. 1 The 
solution is acidified with hydrochloric acid and is heated to 
boiling to decompose the carbonates that are present and to 
expel the excess of bromine. A solution of barium chloride is 
then added and the precipitate of barium sulphate is collected 
on a filter and is washed, dried, and weighed in the usual manner. 
The amount of sulphur in the gas is calculated from the weight 
of the barium sulphate by means of the formula given on p. 322. 
Young's Volumetric Method for Determination of Sul- 
phur. Young has proposed 2 an indirect volumetric method for 
determining the sulphur in illuminating gas. The solution of 
the sulphates obtained by the Referees' method is treated with 
bromine water in the manner above described and then acetic 
acid is added in an amount sufficient to decompose the ammo- 
nium carbonate 3 that is present. The solution is then made up 
to definite volume and to a measured portion of it there is added 
a measured excess of a standard solution of barium chloride. 
The precipitated barium sulphate is not removed by filtration, 
but solution and suspended precipitate are transferred to a 
platinum or porcelain dish and the whole is evaporated to dryness 
and is then heated to low redness to expel the hydrochloric acid 
and ammonium chloride. The dish is allowed to cool and the con- 

1 If the bromine water contains sulphates, the amount of sulphur in the volume of 
this reagent that is added should be subtracted from the final result. Ammonium 
sesquicarbonate usually contains no sulphate, but it nevertheless should be tested 
for this impurity before being used. 

2 Stone's Practical Testing of Gas and Gas Meters, p. 116. 

3 These chemicals must be free from non-volatile halogen salts. 



328 GAS ANALYSIS 

tents is washed out with distilled water into a beaker. An amount 
of a 10% solution of potassium chroma te sufficient to precipitate 
all of the barium chloride and to color the supernatant liquid 
pale yellow is then added, and a standard solution of silver 
nitrate is run in from a burette until the red color of silver 
chromate remains permanent. The solutions that are here used 

are a solution of silver nitrate that contains 8.449 grams 
AgNOa to the liter and a - solution of barium chloride that 

contains 26.0375 grams BaC^ to the liter. In the calculation 
of results the volume of the gas that has been burned is corrected 
to standard conditions (760 mm., O C.). The volume of barium 
chloride equivalent to the volume of silver nitrate that has 
been added (5 cc. AgNO 3 = i cc. BaCk) is then calculated, 
and this result is subtracted from the volume of barium chloride 
that was added. The remainder represents the amount of 
barium chloride that reacted with the sulphate in the solution. 
Knowing the strength of the solution of barium chloride, the 
actual weight of the barium chloride may then easily be calcu- 
lated, and from this the grams of sulphur in the corrected volume 
of gas that has been burned. This final result should then be 
converted into the amount of sulphur in grams per cubic meter 
of the gas, or in grains per one hundred cubic feet of gas. 

6. The Determination of Cyanogen in Coal Gas 

For the determination of the total cyanogen in illuminating 
gas the method of Nauss (p. 263) may be used. 

PINTSCH GAS 

Pintsch gas is made by the destructive distillation of crude 
petroleum or its distillates. It possesses an illuminating power 
three or four times greater than that of average coal gas, and it 
can be brought under a pressure of ten atmospheres with a loss 
of only ten per cent of its illuminating power. Twenty-five 



ILLUMINATING GAS FUEL GAS 329 

samples of the compressed gas showed on analysis the following 
average composition: 

Heavy Hydrocarbons (Illuminants) 

Benzene, C 6 H 6 ) 

Ethylene, C2H 4 , etc. V . . . . 35 per cent 

Propylene, CsHe j 

Carbon Monoxide, CO . . . . . 0.5 

Hydrogen, H 2 ...... . . 4-5 

Methane, CH 4 I 

Ethane, C 2 H 6 J ' 

In the analysis of a sample of Pintsch gas the constituents 
would be determined in the order already given under illumi- 
nating gas, namely : 

Carbon dioxide by absorption with potassium hydroxide, 

Benzene by absorption with ammonia nickel cyanide and 
5 per cent sulphuric acid, 

Heavy hydrocarbons other than benzene by absorption with 
fuming sulphuric acid and potassium hydroxide, 

Oxygen by absorption with alkaline pyrogallol, 

Carbon monoxide by absorption with ammoniacal cuprous 
chloride, 

Hydrogen by fractional combustion with copper oxide 
(p. 201) or by absorption with palladium-black (p. 188), 

Methane and ethane by combustion with oxygen in the com- 
bustion pipette (p. 149), and calculation of the percentages of 
the two gases by the method set forth on p. 315. 

The high percentage of heavy hydrocarbons in Pintsch gas 
renders it necessary that the treatment of the mixture with the 

[absorbents for these constituents be thorough and sufficiently 
prolonged to insure the complete removal of these gases. 
The large amount of methane and its homologues precludes 
the use of the total residue in the final combustion if, as is 
desirable, the volume of oxygen and the volume of the resulting 
carbon dioxide are to be kept within the capacity of the gas 



330 GAS ANALYSIS 

burette (100 cc.). This is apparent from the equations repre- 
senting the combustion of methane and ethane. 

CH 4 + 2 O 2 = C0 2 + 2 H 2 O 

1 VOl. 2 VOl. I VOl. 

2 C 2 H 6 + 7 O 2 = 4 CO 2 + 6 H 2 O 
2 vol. 7 vol. 4 vol. 

Consequently, in the combustion of methane and ethane in 
Pintsch gas, 100 cc. of oxygen is first passed into the combustion 
pipette and then only such portion of the combustible residue is 
introduced as will ensure the presence of an excess of oxygen in 
the pipette after the combustion is complete. 

It is not possible, by means of one complete combustion, to 
determine more than two hydrocarbons of the methane series 
(see p. 130, First Case). For this reason, if the combustible 
residue contains, in addition to methane and ethane, a higher 
homologue of the series, this third hydrocarbon cannot be de- 
termined by the above procedure. It is usually satisfactory, 
however, to consider that the combustible residue, after the 
removal of hydrogen, contains only methane and ethane and to 
calculate the results on the basis of that assumption. 

PRODUCER GAS BLAST-FURNACE GAS 

In the analysis of these gas mixtures the determination of 
benzene may be omitted but no further special modification 
of the usual procedure is needed unless the combustible residue 
is to be determined by explosion. Producer gas and blast- 
furnace gas frequently contain so small an amount of com- 
bustible gas that the residue will not explode when mixed with 
oxygen or air. In such case pure hydrogen or oxyhydrogen 
gas must be added to the residue (see p. 144). 



CHAPTER XVI 

THE DETERMINATION OF THE HEATING VALUE OF 

FUEL 

The heating value of a fuel is determined by burning a known 
amount of the fuel in an apparatus termed a fuel calorimeter and 
measuring the heat that is produced. 1 

Fuel calorimeters are of two types, continuous and discontin- 
uous. The heating value of solid fuels is usually determined 
with a calorimeter of the discontinuous form, while with liquid 
and gaseous fuel a continuous calorimeter is customarily em- 
ployed. 

i. The Determination of the Heating Value of Solid Fuels 

The most satisfactory and accurate method for the determina- 
tion of the heating value of solid fuel consists in burning a 
weighed amount of the fuel with the aid of compressed oxygen in 
a bomb that is immersed in water. -The heat evolved in the 
combustion warms the water that surrounds the bomb and from 
this rise in the temperature of the water the heating value of the 
fuel is calculated. 

The Bomb. Of the many forms of bombs that have been 
devised, the best known types are those of Berthelot, Mahler, 
Hempel, Atwater, Krocker, Emerson and Langbein. That 
designed by Mahler will here be described. 

The Mahler bomb (Fig. 95) is a steel cylinder B of 10 cm. 
external diameter at the lower end and 14 cm. high, with walls 

1 For full discussion of this subject, see Kalorimetrische Methodik, by W. Glikin, 
IQII; Die kalorimetrische Heizwertbestimmung von Kohle mil besonderer Berucksicht- 
igung der Kalorimetereichung, Jacob, Zeitschrift fur chemische Apparatenkunde, 2 
(1907), 281, 313, 337, 369, 499, 533, 565, 597; Circular of the Bureau of Standards, 
No. II, The Standardization of Bomb Calorimeters. 

331 



332 



GAS ANALYSIS 



8 mm. thick. The outer surface is nickel-plated; the inner 
surface is usually covered with white enamel, although some of 
the finer instruments are lined with platinum or gold. The 

bomb rests in a nickel- 
plated sheet iron saddle H 
which renders possible the 
free circulation of water be- 
tween the bottom of the 
calorimeter vessel and the 
bottom of the bomb. The 
bomb is closed by a steel 
cover C which also is nickel- 
plated on the outside and 
enamelled on the inside. 
The joint between the bomb 
and the cover C is made gas 
tight by setting into the 
top of the bomb a lead 
gasket against which a pro- 
jecting ring R on the under 
side of the cover impinges 
when the cover is screwed 
down into place. Com- 
pressed oxygen is passed 
into the bomb through the 
opening in the stem of the 
needle valve V and the tube 
W. The bomb is closed by 
screwing down the valve V 
until the conical lower end 
is pressed against the open- 
ing that leads into the bomb. 
A platinum rod P passes 
through the cover of the 
FIG. 95 bomb and is insulated from 




DETERMINATION OF HEATING VALUE OF FUEL 333 

the metal of the cover. Another platinum rod S, about one 
mm. in diameter and of the form shown in the figure, is 
fastened to the lower end of P by means of a small bind- 
ing post. A platinum rod that carries a platinum plate F is 
fastened by a binding post K to the lower end of S. The 
plate F is about 28 mm. in diameter, and has sides about 
4 mm. high. Soldered to the lower end of the tube through 
which the oxygen is admitted is another platinum rod which 
is joined by a binding post to the platinum rod T. T ex- 
tends downward to the same distance as the branch rod 
from S. 

The fuel is placed in the platinum pan F and is ignited by 
passing an electric current through a fine iron wire of about 
0.15 mm. diameter that is wrapped around the lower ends of the 
wires 6* and T and rests against the fuel. 

Preparation of Sample of Coal. The substance, usually 
coal, whose heating value is to be determined, should be accu- 
rately sampled and pulverized to pass a loo-mesh sieve. Coal 
should be air-dried, the loss in weight on drying being deter- 
mined and the heating value calculated back to the undried 
coal. 

The sample of the air-dried coal that is to be used for the 
combustion may be handled with greater convenience and with 
less danger of loss if the coal is first compressed into a compact 
mass or briquet by means of such a press as that shown in Fig. g6. 
The cylindrical opening A in the steel block H is filled with the 
powdered sample which is then compressed to a coherent mass 
by turning the bar B and driving down the plunger C. The 
small cylinder of coal is then pushed out of A by turning the 
screw 5 upward, inserting the steel plate P that carries H into 
the slot KK and again driving down the plunger C upon the 
coal cylinder in A . 

This compression of the coal to the form of a briquet does not 
appear to be necessary, so far as accuracy of result is concerned, 
in the case of anthracite coals. These coals may be weighed 



334 



GAS ANALYSIS 



B 





FIG. 96 



DETERMINATION OF HEATING VALUE OF FUEL 335 

in powdered form directly into the platinum pan F. With bitu- 
minous coal, however, it frequently happens that an appreciable 
amount of the powdered sample is thrown out of the platinum 
pan by the violent escape of volatile matter during the combus- 
tion in the bomb, and, after the combustion, the interior of the 
bomb will frequently be found to be covered with a fine, black 
dust. The degree to which a powdered bituminous coal may 
escape combustion in the bomb is shown by the results of an 
examination into this subject made for the author by Mr. N. R. 
Beagle. Mr. Beagle found that it was practically immaterial 
whether an anthracite coal be compressed into a briquet or 
burned in the powdered form. But with a bituminous coal he 
obtained an average result of 7170 calories per gram when the 
fuel was burned in the powdered form and 7308 calories per 
gram when the bituminous coal was briqueted. The interior of 
the bomb after combustion showed unburned coal dust in each 
case when powdered coal was used, whereas when the coal 
briquet was employed, none of this powder was visible after 
combustion. 

If the coal is compressed, the little cylinder of coal is freed 
from coal dust by brushing it with a camals' hair brush and is 
then trimmed with a knife to the proper weight. The coal 
sample should weigh about one gram. The sample, E, is then 
placed in the platinum pan F and is accurately weighed. 

The Calorimeter. The calorimeter vessel is a nickel-plated 
metal cylinder / (Fig. 97) that should be just large enough to 
permit of complete immersion of the bomb and thorough stirring 
of the water. It is supported in a double- walled metallic vessel K 
that is enamelled on the surface next to the calorimeter, and is 
provided with a metallic cover that has openings, w w, through 
which this jacket may be filled with water. This vessel is further 
covered on the sides and top and bottom with a layer of felt 
about one centimeter thick. The calorimeter vessel is placed 
within the jacket vessel K in the position shown in the figure and 
this inner opening of K is provided with a cover R that is made 



336 




FIG. 97 

in two pieces and that has openings through which pass the 
thermometer T and the rods of the stirrer 55. The thermometers 
that are used in this work are usually filled with mercury and 



DETERMINATION OF HEATING VALUE OF FUEL 337 

have the scale marked on the stem. They should cover a range 
of 10 to 15 C. with graduations in 0.01, or should be of the 
Beckmann type with a scale range of about six degrees. Before 
being placed in use the thermometers should be tested and the 
corrections for errors in the scale ascertained. The stirrer may 
be run by a motor or may be operated by hand. The stirring 
should be slow and in all cases as uniform as possible. 

The calorimeter vessel should not rest directly upon the metal 
jacket but should stand upon supports PP of glass, porcelain 
or ebonite. The stirrer should be of the screw type, but should 
move straight up and down. The rotary movement of the stir- 
rer in the usual form of Mahler calorimeter makes it impossible 
to adequately cover the inner calorimeter vessel. 

Preparation of the Bomb. Clean the inside of the bomb 
and polish the nickel surface of the bomb and its cover. Place 
the cover of the bomb in an upright position in a clamp or on 
a ring stand. Wind a piece of iron ignition wire (see above) 
about 3 cm. long around a pin to give it spiral form and then 
weigh the wire. If the apparatus is in frequent use, it will be 
found more convenient to ascertain the weight of the ignition 
wire per linear centimeter and then to measure the length of 
the piece that is used. 

Wrap the ends of the ignition wire around the platinum wires 
6 1 and T (see Fig. 95). Clean the platinum plate F, place within 
it the weighed coal briquet E or the powdered coal, and then 
fasten it to 5 by means of the small binding post K in such posi- 
tion that the spiral of ignition wire rests lightly against the top 
of the coal. 4 

Introduce from 0.5 to one cc. of water into the bomb, place 
upon the bomb the cover carrying the coal sample, screw down 
the cover with the hand, and finally set it down firmly with a 
wrench. 

To fill the bomb with compressed oxygen, proceed as follows: 

Connect to U, Fig. 95, by means of a nut the flexible copper 
tube L (Fig. 98) that leads to the manometer M and the oxygen 



338 




FIG. 98 
tank O. 1 Open the valve of the oxygen tank slowly and allow the 

1 The oxygen should of course contain no combustible gases such as carbon mo- 
noxide, hydrogen or hydrocarbons. 



DETERMINATION OF HEATING VALUE OF FUEL 339 

pressure in the bomb to rise to about five atmospheres. Close the 
valve of the bomb, disconnect the copper tube L, and then care- 
fully open the valve F, Fig. 95. This operation serves to rinse 
out the bomb with oxygen and thus to remove the greater part 
of the nitrogen of the air that was originally in the bomb. This 
is done to prevent the formation of an appreciable amount of 
nitric acid from atmospheric nitrogen during the combustion. The 
correction for the heat of formation of nitric acid is, however, 
usually less than six calories, a value so small that the rinsing 
of the bomb with oxygen may be omitted in most commercial 
work. 

Now connect L again with U, open the valve of the oxygen 
tank carefully and fill the bomb with oxygen to a pressure of 
25 atmospheres. Close the valve V and disconnect L. 

Combustion of the Sample. Fill the jacket space of the 
calorimeter with water of a temperature about that of the room. 
Place the bomb, prepared for the combustion as above described, 
in the calorimeter and connect its terminals by wires with the 
apparatus that is to furnish the electric current for the heating 
of the iron ignition wire. Storage cells or dry cells that will 
yield a current of a potential of not more than 15 volts should 
be employed. If a no- volt lighting circuit is used there is 
danger of arcing and consequent evolution of heat within the 
bomb. The battery and ignition wire should previously be 
tested to make sure that the current will heat the wire to in- 
candescence in the space of one second. Pour into the calo- 
rimeter vessel that contains the bomb a weighed amount of 
water of a temperature of from ij4 to 2 below that of the 
room. The same amount of water should be used in all com- 
bustions. The volume necessary for the complete immersion 
of the bomb will vary in different calorimeters from about 
2200 cc. to 2700 cc. 

Introduce the stirrer and the thermometer and then put on 
the cover of the calorimeter. Begin stirring and continue it 
for about five minutes. At the end of this time the temper- 



340 GAS ANALYSIS 

ature should be constant or should be regularly and only 
slightly rising or falling. Now begin readings of the thermom- 
eter in the calorimeter, noting the time in hours, minutes and 
seconds, and repeat these readings every minute for a period 
of five minutes in all. These five readings cover what is termed 
the "preliminary period." Throughout the whole experiment 
the water in the calorimeter should be stirred at a uniform rate 
between all readings. 

At the end of the preliminary period, throw in the switch 
(preferably exactly on an even minute) and ignite the sub- 
stance. Throw out the switch at the end of one second. Read 
the thermometer every twenty seconds, recording the time of 
each reading as before. Continue these readings every twenty 
seconds until the maximum temperature has been reached 
and the temperature begins to fall. This ends the "middle 
period." 

From this point make readings one minute apart over a period 
of time equal to the length of the preliminary period. This 
constitutes the "after period." Remove the bomb from the 
calorimeter and slowly open the valve to relieve the excess of 
gas pressure within the bomb. Then unscrew the cover of the 
bomb and examine the interior of the bomb to make sure that 
the fuel was completely burned. 

The Water Equivalent of the Calorimeter. When a sam- 
ple of fuel is burned in the bomb, the greater part of the heat 
that is evolved is transferred to the surrounding water which is 
thereby raised in temperature. The remainder of the heat is 
taken up by the apparatus itself. Each particular apparatus will 
have a definite heat capacity of its own, which will be different 
from that of another apparatus even of the same type. It is cus- 
tomary to express the heat capacity of the instrument in terms 
of the number of grams of water that would be raised iC. in 
temperature by the heat absorbed by the apparatus. This 
result is termed the Water Equivalent of the calorimeter. It 
should experimentally be ascertained with great care for each 



DETERMINATION OF HEATING VALUE OF FUEL 341 

instrument, because an error in this will affect all determina- 
tions made with the calorimeter. 

The water equivalent of most of the bomb calorimeters now 
on the market is determined by the manufacturer and is marked 
upon the instrument. If, however, the calorimeter is not so 
marked, or if the operator deems it desirable to ascertain the 
correctness of the marking, the water equivalent of the ap- 
paratus may be determined once and for all 

(a) By weighing the different parts of the apparatus, multi- 
plying the weight of each part by the specific heat of the 
material of which that part is made, and adding the re- 
sults: or 

(b) By the method of mixtures: 1 or 

(c) By setting free a known amount of heat within the bomb 
and ascertaining the resulting rise of temperature of the water 
in the calorimeter vessel. The most accurate results by this 
method are obtained by the insertion of an electric resistance 
heater within the bomb, but usually the determination is made 
by burning in the bomb a weighed sample of a combustible 
substance whose heat of combustion has accurately been as- 
certained. 

Standard Combustible Substances. The combustible 
substances in most general use as standards are cane sugar, 
benzoic acid and naphthalene. Samples of these substances, 
specially prepared for this purpose, may be obtained from the 
Bureau of Standards at Washington. Circular No. n of the 
Bureau contains the following statement concerning these three 
materials : 

" Sucrose is not volatile nor strongly hygroscopic, but is rather 
difficult to ignite and sometimes does not burn completely. 
It has a heat of combustion of about 3950 calories, or only 
about half that of the average coal. The more exact value for 
each sample will be given in the certificate. 

"Benzoic acid is only slightly volatile, is not very hygroscopic, 
1 See Jakob, Z. f. chem. Apparatenkunde, n (1907), 533. 



342 



GAS ANALYSIS 



has a heat of combustion of about 6320 calories and burns more 
readily than sugar. 

"Naphthalene is quite volatile but not hygroscopic; it has a 
heat of combustion of about 9610 calories, a little higher than 
that of most coals, and it ignites and burns very readily. 

"Of these materials probably the most satisfactory for work 
of the highest accuracy is benzoic acid, but for calibration of 
commercial calorimeters to an accuracy of o.i per cent naph- 
thalene has some advantages. The loss by sublimation from 
samples of naphthalene made up into briquets will hardly ex- 
ceed o.i or 0.2 per cent in an hour." 

This last mentioned method is the most satisfactory for the 
calibration of commercial calorimeters. It is carried out as fol- 
lows: Compress some of the standard combustible substance in 
the press into the form of a briquet, trim it down until it weighs 
about one gram, 1 free it from loose particles and dust, and burn 
it in the calorimeter in the manner already described. 

EXAMPLE OF THE DETERMINATION OF THE WATER EQUIVA- 
LENT OF A CALORIMETER 
Readings on Beckmann Thermometer During the Experiment 



PRELIMINARY PERIOD 


MIDDLE 


PERIOD 


AFTER 


PERIOD 


Time Temp. 


Time 


Temp. 


Time 


Temp. 


2:30:00 2.430 


2:35:20 


2-54 


2:41:30 


4-750 


31:00 2.434 


36:00 


3-26 


42:00 


4-747 


32:00 2.438 


36:20 


4.16 


43:00 


4-743 


33:00 2.443 


36:40 


4.46 


44:00 


4-737 


34:00 2.446 


37:00 


4.62 


45:00 


4-732 


35:00 ^2.450 
Sample ignited 


37:20 
37:40 


4.70 
4-73 


46:00 

- - 


4-728 




38:00 


4-75 








38:20 


4-751 








38:40 


4-752 








39:00 


4-753 








39:20 


4-753 








39:40 


4-753 








40:00 


4-753 








40:20 


4-753 








40:40 


4- 753 








41 :oo 


4-753 







1 The amount of the substance should be such as will cause about the same rise in 
temperature in the calorimeter as that which results from the combustion of about 
one gram of the fuels that are later to be tested. 



DETERMINATION OF HEATING VALUE OF FUEL 343 

Weight of sample of benzoic acid . . i . 0020 grams 

Weight of water in calorimeter , . . 2250 grams 

Weight of iron ignition wire . '. . . 0.004 gram 

Pressure of oxygen in the bomb . . . 25 atmospheres 



Reading of thermometer at end of middle 

period . . ... . . 4-753 

Reading of thermometer at beginning of 

middle period ........ 2.450 

Observed rise of temperature . . . . 

Radiation correction (see below) 

Corrected rise of temperature .... 2.322' 



Heat of combustion of benzoic acid in cal- 
ories per gram . . 6 32O 

Heat evolved by combustion of sample of 

benzoic acid taken .^ .... 1.0020 X 6320 = 6332.6 cals. 

Heat of combustion of iron in calories per 

gram l6oo 

Heat evolved by combustion of ignition 

wire .... 0.004 X 1600 = 6. 4 cals. 

Heat evolved by combustion of sample . 6 339 ca | s 



Total weight of water that would be raised 

i C. in temperature by heat evolved . 6339 

2 322 = 2 73 grams. 

Water equivalent of calorimeter, or total 
weight of water that would be raised one 
degree in temperature, less the weight of 
the water in the calorimeter vessel . . 2730 2250 = 480 grams. 



The Radiation Correction. If the calorimeter could be per- 
fectly insulated from its surroundings, the only temperature 
observations that would be necessary for the determination of 
the water equivalent of the apparatus or of the heating value of a 
fuel would be the temperature of the water before the ignition 
and after the combustion. Perfect insulation is, however, im- 
possible, and there is a continuous transfer of heat between the 
calorimeter and its surroundings, due to conduction, radiation, 



344 GAS ANALYSIS 

convection currents of air and evaporation of water in the calo- 
rimeter. This heat transfer will affect the thermometric readings 
and consequently a correction, termed the radiation correction, 
must be applied to eliminate the errors due to gain or loss of 
heat by the calorimeter during the determination. Among the 
various methods for ascertaining the radiation correction that 
are in use, 1 the following will be found satisfactory and suffi- 
ciently accurate for commercial work. In this, the average rate 
of heat transfer between the calorimeter and its surroundings 
during a period of, say, five minutes, before the ignition of the 
fuel, "Initial Radiation Rate," and for a like period after the 
maximum temperature resulting from the combustion has been 
reached, "Final Radiation Rate," is computed. The time at 
which the mean temperature of the combustion period is reached 
is then calculated, and the initial radiation correction is com- 
puted for the first part of the middle period, and the final radia- 
tion correction for the last part. From these results the corrected 
rise in temperature during the combustion is obtained. The 
radiation correction is determined for each run of the calorimeter. 
In the example of the determination of the water equivalent of 
the apparatus given above the radiation correction is calcu- 
lated in the following manner: 

Radiation Rate, Preliminary Period, = 

2.450 -2.430 o 



5 
Radiation Rate, After Period, = 

4.753 - 4.728 
5 



= 0.005 per minute 



1 See Experimental Engineering by Carpenter and Diederichs, 7th ed., 1911, 
p. 482. 

2 This correction is positive if the temperature is falling during the preliminary 
period and negative if it is rising. 

3 This correction is positive if the temperature is falling during the after period 
and negative if it is rising. 



DETERMINATION OF HEATING VALUE OF FUEL 345 



Mean Temperature of Middle Period 



2.450 + 4-753 



Time at which mean temperature was reached (ascertained by 

plotting curve, or by interpolation), 2:36:10. 

Portion of middle period to which correction for "preliminary" 

radiation rate is to be applied, 2:36:10 2:35 = 

i min., 10 sec. = i^ min. 

Portion of middle period to which correction for "after" radia- 
tion rate is to be applied, 2:41:00 2:36:10 = 
4 min., 50 sec. = 4-f- min. 

Radiation Correction = 
0.005 X 4-jj- 0.004 X * e = - OI 9 

Example of the Determination of the Heating Value of a 
Sample of Coal. 

Weight of sample of coal i . 0050 grams 

Weight of water in the calorimeter . . 2250 grams 
Weight of iron ignition wire .... o . 004 gram 
Pressure of oxygen in bomb .... 25 atm. 



PRELIMINARY PERIOD 


MIDDLE 


PERIOD 


AFTER 


PERIOD 


Time Temp. 


Time 


Temp. 


Time 


Temp. 


11:02:00 2.QIO 
03 2.916 
04 2.922 
05 2.928 
06 2.934 


11:07:20 
07:40 
08:00 
08:20 
08:40 


2.96 
3-03 
3-18 
3-70 

4.22 


11:14:00 
15:00 
1 6:00 
17:00 
1 8:00 


5-498 
5-493 
5-490 
5.486 
5-482 


07 2.940 
Coal ignited 


09:00 
09:20 
09:40 


4.70 
5-06 
5-26 








10:00 
10:20 


5-40 
5.46 








10:40 


S-49 








11:00 


5-500 








11:20 


5-Soi 








11:40 


5-502 








12:00 


5-502 








12:20 


5-502 








12:40 


5-502 








13:00 


5-502 







346 GAS ANALYSIS 

From these data the heating power of the coal is calculated by 
use of the formula: 

(W + E) (T * R) - C 
1 = 



in which H represents the heating value of the fuel, W the weight 
of the water in the calorimeter vessel, E the water equivalent of 
the calorimeter, T the rise in temperature caused by the com- 
bustion, R the radiation correction, C the heat of combustion of 
the iron ignition wire, and G the weight in grams of the sample 
of fuel. 
In the above example 

W = 2250 grams 

E = 480 grams 

T = 2.562 C. 

R = + 0.007 C. 

C =6.4 calories 1 

G = 1.0050 grams 
(W + E) (T + R) C 
~G~ 

(2250 + 480) (2.562 + 0.007) 6.4 

=6972 calories per gram. 

1.005 

It is customary in this country to express the heating value of 
a fuel in terms of British thermal units 2 (B. T. U.) per pound of 

1 Correction is sometimes introduced for the heat of formation of nitric acid that 
is formed by the oxidation of nitrogen gas in the bomb. This is done by washing 
out the bomb with distilled water after the combustion and titrating the acid with 
a standard solution of an alkali. The correction is so small that it may be disre- 
garded in commercial work. If the bomb is rinsed with oxygen gas before the com- 
bustion, the amount of nitric acid that is formed from the atmospheric nitrogen in 
the bomb will be so slight as to be negligible even in quite accurate work. Moreover 
sulphurous acid and sulphuric acid that result from the combustion of the sulphur 
in the coal are frequently found in the bomb after the combustion. The presence 
of these compounds will vitiate the titration results for nitric acid. Furthermore 
their heat of formation should not be subtracted from the heating value of the fuel. 

2 A British thermal unit is the amount of heat required to raise the temperature 
of one pound of water one degree Fahrenheit. 



DETERMINATION OF HEATING VALUE OF FUEL 347 

coal, instead of in calories per gram. The latter expression 
multiplied by 1.8 gives the B. T. U. per pound. Consequently 
in the foregoing example 

H = 6972 x 1.8 = 12549.6 B. T. U. per pound. 

2. The Determination of the Heating Value of Liquid and Gaseous 

Fuels 

The heating value of some liquid fuels may be determined 
by dropping the liquid on a small cellulose block 1 and then 
burning this in the usual manner in a bomb calorimeter. The 
determination is, however, customarily made with a calorim- 
eter of the continuous type, such as that devised by Junkers. 
This instrument is primarily designed for use with gaseous fuels, 
but by means of special attachments it may be employed with 
liquid fuels as well. 

The Junkers Gas Calorimeter 

The calorimeter (Fig. 99) consists of an upright combustion 
chamber 28 through which the products of combustion from 
the flame 27 first rise, then pass downward through thin-walled 
copper tubes (shown in the cross section) and finally escape 
through ji and 32. The rate of escape of these gases is controlled 
by the damper jj and their temperature is shown by a thermome- 
ter inserted through an opening in the top of the pipe 32. The 
water vapor in the combustion gases is partially condensed and 
this condensed water flows out through 35. Cold water enters 
the apparatus at 3, passes downward through 6, rises around 
the bulb of the thermometer ij and then enters the calorimeter 
and passes upward through the space around the heating tubes. 
At the top of the calorimeter the warmed water flows through 
the perforated plates 38' which have staggered holes to promote 
thorough mixing. It passes out of the apparatus through 18, 20 
and 21 either to the measuring apparatus or to waste. The 

1 See Kellner, Landwirtschaftl. Versuchsstat., 47 (1896), 275. 



348 GAS ANALYSIS 

water is warmed in its passage through the calorimeter; the 
temperature of the inlet water is measured by the thermometer 




FIG. 99 

15 and that of the escaping water by the thermometer 43. The 
calorimeter is surrounded by a polished nickel-plated jacket 
36. The rate of the flow of the water is regulated by means of 



DETERMINATION OF HEATING VALUE OF FUEL 349 

the plug cock 9 and a pointer and scale shown in the figure to 
the right, and the head is kept constant by the overflow device 4. 
The rate of flow of the gas whose heating power is being deter- 
mined is regulated by the cock 22. 

The rate of flow of the water and the gas should be so ad- 
justed that 

(1) the escaping gases shall have approximately the same 
temperature as the surrounding atmosphere, and 

(2) the difference in the temperatures of the entering water 
and the escaping water shall be from 5 to 10, or sufficiently 
great to permit of accuracy in the heat calculations. 

The determination of the heating power of a gas by the Jun- 
kers method is carried out as follows: 

Preparation of Apparatus. Level and adjust the experi- 
mental gas meter G (Fig. 100) and the pressure regulator at its 
right, and fill each with the proper amount of water. Connect 
them together with tubing and connect the inlet tube of the gas 
meter with the holder or main containing the gas to be examined. 
Attach the burner to the outlet tube of the pressure regulator by 
means of rubber tubing, place the burner on the table, turn on 
the gas and light it at the burner. Allow the gas to burn for 
about fifteen minutes to insure the saturation of the water in the 
meter and pressure regulator with the constituents of the gas mix- 
ture, and the removal of air from these instruments and from the 
connecting tube. In the meantime place the calorimeter in the 
position shown in the figure, and level it by means of the screws 
at the lower ends of the legs. The apparatus should be protected 
from drafts, and the temperature of the room should be as nearly 
constant as possible. Place the thermometers 73, 43 and 32, 
Fig. 99, in place and connect 3 with the water supply by means of 
a rubber tube. The entering water should have a temperature 
slightly lower than that of the room. Turn on the water, and 
by means of the pointer E adjust its rate of flow so that some 
of the entering water will overflow and pass out through 4 
and 5. 



350 



GAS ANALYSIS 



Regulate the air supply to the burner to give a flame with a 
slightly luminous tip which will insure the perfect combustion of 
the entering gas and will prevent the cooling of the flame through 
an excess of air. 




G 



; Tb drain 



FIG. 100 



Now insert the burner in the combustion chamber and screw 
it firmly into place in such position that the vertical tube will 
project about 12 cm. upward into the combustion chamber. A 
mirror held at an angle below the combustion chamber will 
enable the operator to see into the chamber and observe whether 
the burner is set in place in the middle of the chamber and 
whether the gas is burning properly. 



DETERMINATION OF HEATING VALUE OF FUEL 351 

Regulate the water supply by means of the pointer so that 
there is a difference of from 5 to 10 between the temperatures 
of the entering water and of that leaving the calorimeter. Read 
the thermometer inserted at 32 and note whether the escaping 
gases have approximately the temperature of the room. If 
they have not, adjust the rates of flow of the water and gas 
until this result is attained. When the temperatures of the 
escaping water and of the escaping gases have become constant 
and the condensed water has begun regularly to drop from the 
tube 35 the actual determination of the heating value may be 
begun. 

Determination of the Heating Value of the Gas. Read 
and record the prevailing barometric pressure, the temperature of 
the gas in the meter and the pressure of the gas on the manome- 
ter of the regulator. At the moment that the large hand of the 
gas meter passes the zero mark, note the position of the small 
hand of the meter and at once insert into the graduated cylinder 
of 2000 cc. capacity the rubber tube C that is connected with the 
outlet 21 and that has up to this time been connected with the 
drain. Place a 100 cc. graduated cylinder under the tube 35 to 
catch the condensed water. When the large graduated cylinder 
becomes filled to the upper mark it is replaced for the moment 
by a beaker and is emptied. It is then immediately returned 
to its position under the rubber tube and the water that has 
run into the beaker is poured into the cylinder. The number 
of times that the cylinder is emptied during the determination 
must, of course, be accurately recorded. 

Read the thermometers 1 3 and 43 at one-half minute intervals. 
When from 30 to 50 liters of gas has been burned, note accu- 
rately the reading of the gas meter and at once remove the rubber 
tube from the large cylinder and withdraw the small cylinder in 
which the condensed water is being collected. Record the vol- 
ume of water that has been measured in the large cylinder and 
the volume of the condensate that is collected in the small gradu- 
ated cylinder. Again read the temperature of the gas in the me- 



352 GAS ANALYSIS 

ter and the pressure that is shown on the manometer of the regu- 
lator. Then turn off the gas and after this has been done, shut 
off the water. 

Calculation of Results. Average the readings of the tem- 
perature of the gas in the meter and of the pressure on the ma- 
nometer of the regulator at the beginning and the end of the ex- 
periment and use the mean values in the calculation of results. 

Reduce the volume of gas that has been burned to the volume 
that it would occupy under standard conditions with the aid of 
the formula 

p+ s m 

VQ = 1) 

760 (l + 0.00367 /) 

in which 

VQ represents the volume of the gas, in liters, under standard 
conditions, 

v represents the volume of the gas, in liters, under the pre- 
vailing conditions, 

p represents the barometric pressure in millimeters of mercury, 

5 represents the reading of the manometer on the meter, in 
millimeters of mercury, 

m represents the tension of water vapor at t, in millimeters 
of mercury, 

/ represents the temperature of the gas in the meter. 

The heat evolved by the combustion of the gas may be ex- 
pressed as total heat, gross heat, or net heat. 1 Rosa defines total 
heat as the amount of heat measured by the calorimeter per 
unit quantity of gas burned, if the air (admitted to the calorim- 
eter at room temperature) is dry, and if all of the water vapor 
formed by combustion is condensed in the calorimeter, and both 
it and the products of combustion escape at room temperature. 
Gross heat is the amount of heat measured by the calorimeter 
when the gas and the air are admitted to the calorimeter at 
room temperature, but are not dry, and when the products of 
combustion are cooled substantially to room temperature be- 

1 Rosa, The use of Gas for Heat and Power, Centenary Celebration Lectures, p. 143. 



DETERMINATION OF HEATING VALUE OF FUEL 353 

fore leaving the calorimeter, these products escaping as gases ex- 
cept for a small amount of water vapor that is condensed and 
collected as water at room temperature. The net heating value 
of a gas is the total heating value minus the latent heat at room 
temperature of all of the water vapor that is formed in the com- 
bustion. 

The gross heating value of the gas may be calculated by 
means of the formula 



in which 

H represents the heating value of the gas expressed in calories 
per liter, 

W represents the number of cubic centimeters of water that 
has been heated, 

T represents the average difference in the readings of the 
thermometers ij and 43, 

V represents the volume of gas in liters, under standard con- 
ditions, that has been burned. 

The net heating value of the gas may be calculated by means 
of the formula 






in which 

H r represents the lower heating value of the gas expressed 
in calories per liter, 

W as above, 

T as above, 

V as above, 

W represents the number of cubic centimeters of water con- 
densed during the combustion of the gas. 

/ represents the temperature of the condensed water escaping 
from 35, Fig. 99. 



354 GAS ANALYSIS 

To express the heating power of a gas in B. T. U. per cubic 
foot, multiply the calories per liter by the factor 0.11236. 

Gross and Net Heating Value. A word of explanation as 
to the meaning of the terms gross and net heating value may not 
be out of place. When a gas that contains hydrogen or com- 
pounds of hydrogen is burned, steam is formed. If this steam 
at 100 is condensed to water at 100 within the heating appara- 
tus, 537 calories are set free for every gram of water thus formed. 
This amount of heat thus becomes available and it, together 
with the heat liberated upon the cooling of the condensed water 
to room temperature, is included in the gross heating value of 
the gas. 

When, however, the gas is used in gas stoves, gas engines or 
for the heating of Welsbach mantles, the steam that is formed 
is not condensed, and consequently its latent heat does not be- 
come available. Deduction of this loss gives the net heating 
value of the gas. 

There is a considerable difference of opinion as to whether 
the gross heating value or the net heating value most accurately 
expresses the calorific power of the gas. A discussion of this 
question will be found in Stone's Practical Testing of Gas and 
Gas Meters. 

Automatic Gas Calorimeter. Professor Junkers has also 
devised an automatic form x of his calorimeter. The under- 
lying principle of the device is the same as that employed in 
the other form of the Junkers apparatus, but the instrument is 
made automatic by rendering constant the ratio of the amount 
of gas burned to that of water passing through the calorimeter, 
in which case the difference of temperature is a direct measure 
of the heating value of the fuel. The temperature difference 
is measured by a thermocouple, the junctions of which are 
immersed in the entering and escaping water. The readings 
are made on a millivoltmeter. 

1 J. Gasbeleuchtung, 50 (1907), 520. 



CHAPTER XVII 
ACETYLENE GAS 

The chief object of the analytical examination of acetylene 
is the detection and determination of certain impurities in the 
gas rather than the determination of acetylene itself. 

Impurities in Commercial Acetylene. Commercial calcium 
carbide may be contaminated with metallic calcium, calcium 
phosphide, calcium sulphide, aluminum carbide, aluminum ni- 
tride, magnesium nitride, or calcium nitride; consequently in the 
analysis of acetylene the following impurities have to be con- 
sidered, hydrogen, ammonia, phosphine, organic compounds 
of phosphorus, hydrogen sulphide, organic compounds of sulphur, 
silicon hydride, carbon monoxide, 1 methane (oxygen, nitrogen). 

Of these, hydrogen, carbon monoxide, methane, oxygen, and 
nitrogen need not usually be determined since they are, as a 
rule, present in only small amounts, are without appreciable 
effect upon the luminosity of the acetylene flame, arid, if they 
are susceptible of oxidation under the prevailing conditions, 
yield products that are not objectionable* On the other hand, 
ammonia, phosphine, organic compounds of phosphorus, hy- 
drogen sulphide, organic compounds of sulphur, and silicon 
hydride should be tested for and, if found to be present, should 
be determined, because, upon combustion of the gas, nitric acid 
is formed from ammonia, phosphoric acid from phosphine and 
other compounds of phosphorus, sulphurous acid and sulphuric 
acid from hydrogen sulphide and other compounds of sulphur, 
and silicon dioxide from silicon hydride. These products of 
oxidation vitiate the air and attack or clog the metal parts of 
the burner. 

1 Keppeler, J. Gasbdeuchtung, 45 (1902), 804. 
355 



356 GAS ANALYSIS 

Sampling of Calcium Carbide. The analyst may at times 
be called upon to analyze acetylene gas itself, but more often 
he is given a sample of calcium carbide and is asked to report 
upon the purity of the acetylene that is evolved from it. As 
commercial calcium carbide is usually far from uniform in com- 
position, trustworthy results as to the purity of the acetylene 
that it yields can be obtained only from an average sample that 
is prepared from a fairly large amount of the carbide. Such a 
sample of the carbide cannot, however, be prepared in the usual 
manner by breaking the lumps into small pieces, grinding these 
to a powder, and mixing the powder. The substance is so 
hard that considerable time would be required to pulverize 
the pieces, and during the work the moisture of the air would 
decompose an appreciable amount of the carbide. The best 
that can be done under the circumstances is to rapidly break 
up the carbide into pieces about the size of a pea, to sift these 
without delay to remove the carbide dust, to then roughly mix 
the pieces of carbide together, and to place the material thus pre- 
pared in dry, tightly stoppered bottles. A sample prepared in 
this manner, is, of course, far from being homogeneous, and for 
this reason the portion of carbide taken for a determination 
should amount to about fifty, or even one hundred, grams. 

Determination of Hydrogen in Acetylene. Hydrogen in 
crude acetylene results from the action of metallic calcium upon 
the water used to decompose the calcium carbide, or from 
polymerization of acetylene and splitting off of hydrogen 
when the gas is generated at high temperature. 

Hydrogen in acetylene may be determined with the Hempel 
apparatus by absorbing the acetylene with fuming sulphuric 
acid, oxygen with alkaline pyrogallol, the last traces of acetylene 
with ammoniacal cuprous chloride, and determining hydrogen 
(and methane if present) in the residue by combustion. 

Determination of Ammonia in Acetylene. Ammonia is 
formed by the action of water upon metallic nitrides, as 
Mg 3 N 2 + 3 H 2 O = 3 MgO + 2 NH 3 



ACETYLENE GAS 357 

Lewes determines ammonia in crude acetylene by passing 
the gas through a solution of sulphuric acid of known strength 
and ascertaining the excess of sulphuric acid by titration of the 
solution with fo ammonium hydroxide, using litmus as indi- 
cator. 

Determination of Phosphine in Acetylene. Phosphine is 
almost always present 1 in crude acetylene. It is due to the 
reaction between calcium phosphide and water. If the acetylene 
is evolved at high temperature, as is frequently the case when 
water is allowed to drop upon the calcium carbide, organic phos- 
phorus compounds may also be formed, but if appreciable rise 
of temperature during the generation of the gas is avoided, the 
amount of these organic substances is negligible, and all of the 
phosphorus that is present may be assumed to exist in the form 
of phosphine. 

The amount of phosphine in crude acetylene is quite variable, 
but it usually lies between .03 per cent and 1.8 per cent. 2 The 
regulations of the British Acetylene Association state that " car- 
bide which, when properly decomposed, yields acetylene con- 
taining from all phosphorus compounds therein more than 0.05 
per cent by volume of phosphine, may be refused by the buyer, 
and any carbide found to contain more than this figure, with a 
latitude of .01 per cent for the analysis, shall lie at the risk and 
expense of the seller. ..." If the permissible maximum of 
phosphine lies in the neighborhood of .05 per cent by volume, 
it is apparent that the determination of this gas in crude acety- 
lene cannot satisfactorily be accomplished by a volumetric 
absorption method that uses a sample of only one hundred cc. 
of acetylene. 

Of the methods that have been proposed for the determina- 
tion of the gaseous compounds of phosphorus in acetylene, the 

1 Vogel, Handbuchfur Acetylen, p. 232. 

2 Vogel, loc. tit., p. 234. The analyses given by Fraenkel, /. Gasbeleuchtung, 51 
(1908), 431, show from .024 to .057 per cent by volume of phosphine in crude acety- 
lene. 



3$8 GAS ANALYSIS 

combustion method developed by Eitner, 1 Keppeler, 2 and Fraen- 
kel, 3 and the sodium hypochlorite absorption method of Lunge 
and Cedercreutz 4 are in most general use. The first of these 
methods, in which the phosphorus in crude acetylene is deter- 
mined by burning the gas and ascertaining the amount of 
phosphoric acid in the products of combustion, gives the total 
amount of phosphorus, whether it is present in the gas as phos- 
phine or in the form of organic compounds of phosphorus. The 
acetylene is burned in an Acetylene-Bunsen burner under a cylin- 
drical glass hood, and the products of combustion are drawn 
through an oxidizing solution, such as sodium hypochlorite 
or sodium hypobromite. The resulting phosphoric acid is then 
determined by precipitation with " magnesia mixture." On 
account of the difficulty in regulating the pressure of the gas as 
it comes from the evolution apparatus, Fraenkel recommends 
that the acetylene from about 50 grams of calcium carbide be 
collected over a salt solution in a large tubulated bottle, and 
that the gas be then driven from this bottle through the burner. 
This necessitates the use of glass bottles of about 20 liters 
capacity, and if the acetylene is to be mixed with an equal vol- 
ume of hydrogen before combustion, as Fraenkel recommends, 
the containers must be so large as to render them very unwieldy 
and quite expensive. Moreover, the accuracy of the determina- 
tion of phosphorus in the gas will undoubtedly be affected by 
the reaction between the compounds of phosphorus and the 
confining liquid. 

For these reasons the method of Lunge and Cedercreutz in 
which the crude acetylene is passed directly from the generating 
apparatus through a solution of sodium hypochlorite is to be 
preferred to the combustion method if it will yield accurate 
results. The apparatus that was used by these authors is 
shown in Fig. 101. A weighed amount of the calcium carbide 

1 /./. Gasleleuchtung, 44 (1901), 548. 

9 Ibid., 45 (1902), 802. 

3 Ibid., 51 (1908), 431. 

4 Z./. angew. Chem., 1897, 651. 



ACETYLENE GAS 



359 



(from 50 to 70 grams) is placed in the flask B, and there is in- 
serted into the neck of B a rubber stopper that carries a short 
delivery tube and a separately funnel A. The ten-bulb ab- 
sorption tube C is charged with about 75 cc. of a three per cent 
solution of sodium hypochlorite and is connected to the evolu- 
tion flask. Water is now allowed to drop slowly from A upon 
the carbide in B at a rate of from 6 to 7 drops a minute. The 
evolution of acetylene will cease in from three to four hours. 




FIG. 101 

Air is then drawn through the apparatus to carry over into C 
any acetylene that may still remain in B. The contents of the 
absorption tube C is transferred to a beaker and the phosphoric 
acid in the solution is precipitated by magnesia mixture. 

Objection has been raised to this method because the acetylene 
is generated by dropping water upon calcium carbide, which 
is said to give rise to organic compounds of phosphorus that 
will pass through the solution of sodium hypochlorite without 
undergoing complete oxidation, and further because of the prob- 
able incompleteness of the absorption of the evolved phosphine 
by the solution of sodium hypochlorite in the ten-bulb tube. 



3<5 



GAS ANALYSIS 



In seeking to improve this absorption method two points that 
present themselves are, therefore, 

(1) A method of generating acetylene that will avoid ap- 
preciable rise of temperature when the calcium carbide is de- 
composed, and 

(2) An absorption apparatus that is more efficient than the 
ten-bulb tube used by Lunge and Cedercreutz. 

The method described by Dennis and O'Brien 1 seems to 
fulfill these requirements in a most satisfactory manner. 




FIG. i 02 

The evolution of acetylene without marked rise of temperature 
is accomplished in simple fashion by the employment of a small 
Kipp apparatus about 40 cm. high, and with bulbs about 10 cm. 
in diameter. The annular space around the stem between the 
middle and bottom bulbs is covered with a perforated rubber 
disk D (Fig. 102). A solution of sodium chloride, saturated 
at room temperature, is poured into the top bulb until the end 
of the stem in the bottom bulb is covered with the liquid. A 
perforated stopper carrying a short glass tube is inserted in the 
neck of the top bulb, the stopper with exit tube and glass 

l Jour. Ind. Eng. Chem., 4 (1912), 834. 



ACETYLENE GAS 361 

stopcock is inserted in the tubulus of the bulb B, and the further 
end of the outlet tube is connected with the absorption appara- 
tus that contains the solution of sodium hypochlorite. Hydro- 
gen gas is now passed into the upper bulb of the Kipp generator 
and through the absorption apparatus to displace the air. About 
50 grams of the calcium carbide under examination, broken 
into pieces about the size of a pea and sifted to remove the dust, 
is placed in a dry weighing tube and this is at once tightly 
stoppered and weighed. When practically all of the air has 
been displaced from the Kipp apparatus by hydrogen, the stop- 
per in the tubulus of the bulb B is removed, the contents of the 
sample tube is poured into the bulb and the stopper is at once 
reinserted. The current of hydrogen through the apparatus 
is continued for about one minute, the stopcock is then closed, 
and the stopper and tube are removed from the upper bulb of 
the Kipp generator. An additional amount of salt solution 
sufficient to cause the apparatus to function as a gas generator 
is then introduced into the upper bulb. The stopcock is now 
opened to such an extent that the evolved gases pass through 
the apparatus at a rate slightly faster than will permit of the 
bubbles being counted. Under these conditions the decomposi- 
tion of a sample of 50 grams will be effected in about two hours. 
The reaction between the salt solution and the calcium carbide 
proceeds at a uniform rate, and with.no appreciable rise of 
temperature. 

The absorption apparatus that is employed is a Friedrichs 
gas washing bottle modified in form so that the apparatus can 
easily be rinsed out with water at the close of the run. The 
absorbing solution is introduced into the outer cylinder to such 
height that it will stand at the top of the widened foot of the 
cylinder, and the spiral with the ground glass shoulder is then 
inserted. When a gas is passed into the bottle through the 
central tube, it follows the grooves of the spiral when it rises 
and pushes some of the solution ahead of it. These gas wash- 
ing bottles are much more compact than the ten-bulb tube 



362 GAS ANALYSIS 

used by Lunge and Cedercreutz, and experiment has shown 
that the absorption attained by their use is surprisingly rapid 
and complete. The solution of sodium hypochlorite with which 
the absorption apparatus is charged is prepared by dissolving 
15 grams of sodium hydroxide in 100 cc. of water, saturating the 
ice-cold solution with chlorine, driving out the excess of chlorine 
with a current of air, and then determining the amount of sodium 
hypochlorite in the solution by treatment with hydrogen dioxide 
in a Lunge nitrometer (see p. 397). The solution is then diluted 
to three per cent NaCIO, and about 75 cc. of this solution is 
placed in each bottle. 

After the decomposition of the calcium carbide is complete, 
the acetylene that remains in the generator is driven over into 
the absorption bottles by again passing hydrogen through the 
apparatus in the manner above described. The contents of the 
gas washing bottles is transferred to a beaker, the bottles and 
inner tubes being thoroughly rinsed with distilled water. 10 cc. 
of concentrated hydrochloric acid is added to the liquid which 
is then boiled until the odor of chlorine is no longer noticeable. 
Ammonium hydroxide is added to alkaline reaction and the 
phosphoric acid that is present is determined by precipitation 
with magnesia mixture, and weighing as magnesium pyrophos- 
phate. 

The volume of phosphine to which the weight of magnesium 
pyrophosphate is equivalent may be calculated as follows : 

Mg 2 P 2 O 7 : 2 PH 3 = 222.72 : 68.13, 
or weight Mg2P2O7 X 0.3059 = weight phosphine. 



Since one gram of phosphine occupies a volume of 657.9 cc - 
at O C. and 760 mm. pressure, 

volume of PH 3 in cc. = 
weight in grams Mg 2 P2O7 X 0.3059 X 657.9 

or, volume of PH 3 in cc. = 

weight in grams Mg 2 P 2 (>7 X 201.25 



ACETYLENE GAS 363 

Determination of Volume of Acetylene evolved from Sam- 
ple of Carbide. It is customary to report the results as the 
per cent by volume of phosphine in the evolved acetylene. This 
necessitates the determination of the volume of gas that is lib- 
erated by the calcium carbide under examination. The most 
convenient method for making this determination is that pro- 
posed by Bamberger l who places a definite amount of the car- 
bide in a weighed two-neck Wolff bottle of about 400 cc. ca- 
pacity, and runs in upon the carbide an amount of a saturated 
solution of sodium chloride sufficient to entirely decompose 
the substance. The whole apparatus is weighed before and after 
the reaction, and the loss in weight equals the weight of the 
evolved gas which is here assumed to consist entirely of acety- 
lene. The total weight of the Bamberger apparatus before 
the decomposition of the carbide amounts to from 550 to 800 
grams. This weight may materially be reduced by employ- 
ing, in place of the Wolff bottle, an Erlenmeyer flask of about 
250 cc. capacity. This is fitted with a two-hole rubber stop- 
per into one opening of which is inserted the stem of a small 
separatory funnel of 125 cc. capacity; the other opening of the 
stopper carries a U-tube filled with calcium chloride. A sample 
of the calcium carbide amounting to about 50 grams is placed 
in a weighing bottle, is accurately weighed, and is then intro- 
duced into the flask. The stopper carrying the separatory fun- 
nel and the U-tube is then inserted, and the funnel is filled with 
a 20 per cent solution of sodium chloride. The whole apparatus 
is then weighed on a balance accurate to o.oi gram. The total 
weight of this modified form of the Bamberger device is approxi- 
mately 300 grams. The salt solution is now allowed to drop 
slowly upon the calcium carbide, and, after decomposition is 
complete, dry air is passed through the apparatus to expel all 
of the acetylene. The apparatus is then again weighed, the 
difference between the two weighings giving the weight of the 
acetylene evolved. One kilogram of chemically pure calcium 
1 Z.f. Cdc. und Acet., i (1898), 210. 



364 GAS ANALYSIS 

carbide yields 405.93 grams of acetylene, equivalent to 348.4 
liters of acetylene under standard conditions. Assuming that 
the loss of weight in the apparatus equals the weight of the 
acetylene evolved, the volume of the liberated gas may be cal- 
culated as follows: 

Weight of sample : Weight C2H 2 = 100 : x, 

x = the weight of evolved acetylene expressed in per cent 
of weight of the calcium carbide. 

Since pure calcium carbide will yield acetylene amounting to 
40.593 per cent of the weight of the calcium carbide, 

40.593 : per cent C2H2 by weight = 348.4 : x, 

x = the number of liters of acetylene evolved from one 
kilogram of the calcium carbide under examination, or the 
number of cubic centimeters evolved from one gram of the car- 
bide. 

Calculation of Results. From the above data the per cent 
by volume of the phosphine in the acetylene may now be cal- 
culated. An example of such a calculation follows : 

A. Determination of Phosphine 

Calcium carbide taken = 50.3548 grams. 
Weight of Mg2P2O7 = 0.0089 gram 

cc. PH 3 from i gram CaC2 = 0.0089 X 201.25 

50-3548 

B. Determination of Yield of Acetylene 

Calcium carbide taken = 41.071 grams 
Loss of weight of apparatus = 14.4885 grams 

41.071 : 14.4885 = 100 : per cent C2H2 by wt. 
Per cent C2H 2 by weight = 35.28 

40.593: 35.28 = 348.4 : cc. C 2 H2 from i gram CaC 2 
Volume C2H2 from i gram CaC 2 =300 cc. 



ACETYLENE GAS 365 

Per cent PHs cc. PH 3 from i gram CaC 2 X 100 



by volume cc. CzRz from i gram CaC2 



= 0.0117 % 



To determine the accuracy of the results yielded by this 
method, it was necessary to ascertain 

(1) Whether the gaseous compounds of phosphorus that are 
absorbed by sodium hypochlorite would be entirely taken up by 
two Friedrichs gas washing bottles containing the reagent, and 

(2) Whether, in the method here employed for the generation 
of the acetylene, any gaseous compounds of phosphorus are 
evolved that are not absorbed by sodium hypochlorite. 

That complete absorption of the compounds of phosphorus 
is obtained with only two of the gas washing bottles of the type 
here described, even when a sample of carbide unusually high 
in phosphorus was used, was demonstrated by connecting four 
of the absorption bottles in series, charging each with 75 cc. of 
a three per cent solution of sodium hypochlorite and testing 
the contents of each for phosphoric acid after the run. In no 
case was this acid detectable in the third or fourth bottle. 

The second query was answered in two ways. The gases is- 
suing from the second absorption bottle were burned with an 
excess of oxygen, and the products of combustion were found 
to be free from phosphoric acid. In another experiment the 
crude acetylene from the generator was" burned directly with- 
out being passed through the solution of sodium hypochlorite, 
and the result was found to agree with that obtained by the 
absorption method. 

The combustion of acetylene as it issues from a bottle con- 
taining a liquid absorbent has heretofore presented difficulty 
because of the intermittent flow of the gas. It was found, how- 
ever, that complete combustion is easily attained by passing 
the acetylene into the hydrogen inlet tube of a Linnemann 
oxy-hydrogen lamp, admitting oxygen into the other tube of 
the lamp, and insuring continuous combustion by causing a 
small horizontal flame, about one cm. long, of illuminating gas 



3 66 



GAS ANALYSIS 



that is free from phosphorus to burn across the orifice of the 
lamp. 

The accuracy and uniformity of the results obtained with the 
method here described are shown in the following tabulation 
of analyses by the absorption method, and by the method of 
combustion. 

TABLE A 

This sample CaC2 yielded 300 liters C2H2 per kilogram 



No. 


Weight of 
sample in 
grams 


Weight of 

Mg 2 P2O7 

in grams 


PER CENT OF PHOSPHINE IN 
EVOLVED ACETYLENE 


byNaCIO 
method 


by combustion 
method 


I 

2 

3 
4 

6 

8 

9 
10 
ii 


50.3548 
50-3572 
50. 1870 
50.3027 
50 . 0036 
50 - 3047 
50.1625 
50 . oooo 
50 . oooo 
50 . oooo 
50.0612 


.0089 
.0073 
.0062 
.0050 
.0062 
.0059 
0059 
.0072 
.0047 
.0060 
.0062 


.0117 
.0097 
.0083 
.0066 
.0083 
.0078 
.0078 
















.0096 
.0063 
.0080 
.0083 














Average 


.0086 


.0080 



TABLE B 

This sample CaC2 yielded 287 liters C2H 2 per kilogram 



No. 


Weight of 
sample in 
grams 


Weight of 
Mg 2 P 2 7 
in grams 


PER CENT OF PHOSPHINE IN 
EVOLVED ACETYLENE 


byNaCIO 
method 


by combustion 
method 


I 

2 

3 

4 

6 

7 
8 


50.0651 
50.0200 
50.0432 
50.1004 
50 . 0600 
50.1043 
50.0612 
50.0121 


.0661 
.0592 
.0782 
.0582 
.0680 
.0641 
.0601 
.0642 


.0925 
.0829 
.1093 
.0814 










.0948 
.0896 . 
.0841 
.0899 












Average 


.0915 


.0896 



ACETYLENE GAS 367 

The results given in Table A were obtained with a sample 
of commercial calcium carbide. To ascertain whether the 
method would give uniform results when the acetylene con- 
tained a relatively large amount of phosphine, a sample of 
calcium carbide high in phosphorus was prepared, and the 
analyses of this product by the two methods are given in 
Table B. 

Determination of Sulphur in Acetylene. The source of 
hydrogen sulphide in crude acetylene has been the subject of 
considerable discussion. It is commonly thought to be the 
calcium sulphide that is formed when the raw material from 
which the calcium carbide is prepared contains gypsum. But 
Moissan showed l that the product resulting from heating gyp- 
sum and carbon in an electric furnace gave with cold water an 
acetylene free from hydrogen sulphide, and moreover that the 
water used in the reaction after the residue had been removed 
by filtration gave no reaction for hydrogen sulphide. He there- 
fore attributed the presence of hydrogen sulphide in crude 
acetylene to aluminum sulphide, which is easily decomposed 
by water with liberation of hydrogen sulphide. 

In contradiction of this assumption, Wolff 2 found that samples 
of calcium carbide entirely free from aluminum liberated hy- 
drogen sulphide when treated with water. When acetylene is 
set free from calcium carbide in such manner as to avoid ap- 
preciable rise in temperature, the evolved gas seldom contains 
hydrogen sulphide. It is known, however, that when calcium 
sulphide lies in contact with water for a considerable time, it 
changes to a soluble primary sulphide. It is reasonable to sup- 
pose that this change will take place more rapidly at high tem- 
peratures, and consequently when acetylene is set free by drop- 
ping water upon the carbide, hydrogen sulphide may result 
from the action of the water upon calcium sulphide. Moreover, 
Lunge and Cedercreutz found that crude acetylene contains 

1 Compt. rend., 1898, 457. 

2 Z./. Cole, und Acet., I (1898), 272. 



368 GAS ANALYSIS 

sulphur in a form not precipitable by lead acetate which indi- 
cated that the sulphur in the gas was in the form of organic 
compounds of the element. Caro considers l that these volatile 
organic sulphur compounds do not exist in the carbide, but are 
secondary products resulting from the action of hydrogen sul- 
phide upon acetylene. Whatever their source may be, it is a 
fact that crude acetylene contains at times hydrogen sulphide 
and volatile organic compounds of sulphur, and consequently 
these substances must be taken into consideration in a complete 
analysis of the crude gas. 

The determination of sulphur in acetylene may conven- 
iently be combined with the determination of phosphine (see 
under Phosphine, p. 360). The sodium hypochlorite solution 
oxidizes compounds of sulphur to sulphuric acid. Phosphoric 
acid that is simultaneously formed is precipitated by magnesia 
mixture that is free from sulphates. After the ammonium 
magnesium phosphate precipitate has been removed by filtra- 
tion, the filtrate is acidified with hydrochloric acid, heated 
nearly to boiling, and the sulphuric acid precipitated with ba- 
rium chloride. It has been claimed by some that this method 
does not oxidize all of the sulphur compounds in the gas, and 
that accurate results will be obtained only when the crude acety- 
lene is burned and the sulphuric acid is determined in the com- 
bustion products. 

Determination of Silicon Hydride in Acetylene. There 
is considerable difference of opinion as to whether this gas is 
present in acetylene. The work of Lewes and of Fraenkel ap- 
pears to demonstrate its existence in certain samples of crude 
acetylene although the amounts that they found were quite 
small, about o.oi per cent by volume or ten cc. in 100 liters. 
The gas may be determined by the method used by Fraenkel 2 
which consists in burning crude acetylene under a cylinder of 
glass, or better of platinum, rinsing out the cylinder with hy- 

1 Z.f. Cole, und Acet., i (1898), 3 37- 

2 J.f. Gasbeleuchtung, 51 (1908), 433. 



ACETYLENE GAS 369 

drochloric acid and determining the silica that has resulted 
from the combustion. 

Determination of Carbon Monoxide in Acetylene. Kep- 
peler 1 believes that crude acetylene contains a small amount 
of carbon monoxide and bases his belief upon the fact that after 
he had absorbed the acetylene by fuming sulphuric acid in a 
Hempel pipette and had treated the gas residue with potassium 
hydroxide, bromine and phosphorus, there was further ab- 
sorption when the residual gas was passing into a pipette con- 
taining a solution of cuprous chloride. Assuming that this 
absorption was due entirely to carbon monoxide, he found that 
the amount of that gas was about 0.02 per cent of the crude 
acetylene. 

Lundstrom, 2 however, found as much as 1.48 per cent of 
carbon monoxide in acetylene, and Caro as high as 2.3 per cent. 
The source of the carbon monoxide is still in doubt. 

Determination of Methane in Acetylene. From the work 
of Rossel and Sandriset 3 and of v. Knorre and Arndt, 4 it would 
appear that there is no methane in acetylene that has been 
properly generated. If, however, the gas is evolved at high 
temperature, it may contain considerable amounts of methane. 5 
The gas may be determined, together with any hydrogen that 
may be present in the acetylene, by combustion of the non- 
absorbable residue (see under Hydrogen, p. 356). 

Determination of Oxygen and Nitrogen in Acetylene. 
Oxygen and nitrogen may be determined volumetrically by 
the procedure described under hydrogen, p. 356, the nitrogen 
being the gas that remains after the determination of hydrogen 
and methane. 

l J.f. Gasbekuchiung, 45 (1902), 802. 

2 Chemiker-Zeitung, 23 (1899), 180. 

3 Z./. angew. Chem., 1901, 77. 

4 Z. d. Ver. 2. Forderg. d. Gewerbefleisses, 1900, 162. 
6 Lewes, /. Soc. Chem. Ind., 17 (1898), 533. 



CHAPTER XVIII 
EXAMINATION OF ATMOSPHERIC AIR 

Composition of Atmospheric Air. The normal constitu- 
ents of the atmosphere are nitrogen, oxygen, the gases of the 
argon group, carbon dioxide and water vapor. These substances, 
with the exception of water vapor, are present in nearly con- 
stant amount in air that is free from local contamination. 

Nitrogen 78 . i per cent by volume 

Oxygen 20.94 

Carbon Dioxide . . . 0.03 



Argon . 
Neon 
Helium . 
Krypton 
Xenon . 



volume in 106 . 8 volumes of air 

80,800 
245,300 
" " 20,000000 

" 170,000,000 " 



Local conditions may, however, give rise to the presence in air of 
such substances as ammonia, nitrous acid, nitric acid, sulphur 
dioxide, sulphuric acid, carbon monoxide, soot, ozone, 1 etc. The 
possibility of the presence of these and other occasional constit- 
uents in the atmosphere renders it necessary to adopt such 
methods in the examination of air as will meet the demands of the 
special case in hand. The determination of most of the sub- 
stances enumerated above is discussed in Chapter XIII. Two 
constituents, however, water vapor and carbon dioxide, deserve 
special consideration because almost every examination of air 
from a sanitary standpoint involves the determination of these 
two substances. Many methods for rapidly and accurately de- 
termining these constituents of the atmosphere have been de- 

1 See p. 178. 



EXAMINATION OF ATMOSPHERIC AIR 371 

veloped, and a few of the more satisfactory procedures thus far 
devised will here be described. 

A very complete discussion of the history of air analysis, and 
of the amounts of oxygen and carbon dioxide in the atmosphere 
has recently appeared from the pen of F. G. Benedict. 1 

DETERMINATION OF MOISTURE IN THE ATMOSPHERE 

Absolute and Relative Humidity. Water vapor is always 
present in atmospheric air, but the amount varies greatly. 
The maximum quantity of water vapor that can be present in 
any given space is dependent upon the prevailing temperature 
but is independent of the amount of air in that space. When 
this maximum quantity of water vapor is present, the space 
is said to be saturated with water vapor. The quantity of water 
vapor existent in a given space, such as a cubic foot or a cubic 
meter, is termed the " absolute humidity" and may be expressed 
in terms of its weight (in grains or grams) or of its pressure 
(in inches or millimeters of mercury). The ratio between the 
amount of water vapor actually present in a given space and 
the maximum quantity of the vapor that could exist in that 
space at the observed temperature is termed the "relative 
humidity." It is usually expressed in per cent of the maximum 
humidity. 

Wet and Dry Bulb Thermometers. Of the large number 
of methods that have been devised for the determination of the 
amount of water vapor in air, one of the most satisfactory is 
that employed by the Weather Bureau of the United States 
Department of Agriculture. It is based upon the facts that 
water will evaporate as long as the adjacent space is not satu- 
rated with water vapor, and that this evaporation is accompanied 
by the absorption of heat. Consequently, if two thermometers 
are exposed to the air and a moist cloth is placed around the 
bulb of one of them, this "wet bulb" thermometer will show a 

1 The Composition of the Atmosphere. Publication No. 166 of the Carnegie Institu- 
tion of Washington, 1912. 



372 



GAS ANALYSIS 



lower temperature than the "dry bulb" thermometer unless the 
surrounding space is saturated with water vapor. The less the 
amount of moisture in the air, the greater will be the drop in 
temperature of the wet-bulb thermometer. From the final 




FIG. 103 

readings of the two thermometers the amount of water vapor 
then present in the air may be calculated. 

The Whirling Psychrometer. The instrument employed 
by the Weather Bureau for this work is termed the whirling 
psychrometer. Fig. 103. It consists of two thermometers A and B 



EXAMINATION OF ATMOSPHERIC AIR 373 

which are mounted upon arms that can be whirled by turning 
the handle C. The bulb of one thermometer (the "wet bulb") 
is covered with a piece of thin muslin that should first be washed 
to remove sizing. A small rectanglar piece of the washed mus- 
lin, wide enough to go about one and one-third times around the 
bulb, and long enough to cover the bulb and a part of the stem 
above the bulb, is thoroughly moistened with distilled water 
and is neatly fitted around the thermometer. It is first tied 
around the upper end with a piece of strong thread. A loop 
of thread is next passed around the lower end where it projects 
beyond the bulb, and the thread is then drawn tightly around 
the muslin in a knot close up to the lower surface of the bulb 
and the knot is secured. If this is properly done the muslin will 
be neatly stretched over the bulb and securely fastened at the 
bottom. 1 

Manipulation of the Whirling Psychrometer. In making 
a determination of atmospheric moisture the "wet bulb" is 
dipped into a cup of pure water to thoroughly saturate the mus- 
lin with water. The handle C is then turned and the thermome- 
ters are rapidly whirled for from fifteen to twenty seconds. The 
whirling is stopped, and the two thermometers are quickly 
read, the "wet bulb" thermometer being first read. They are 
immediately whirled again and a second reading is taken. This 
is repeated until two successive readings of the "wet bulb" 
agree very closely, which shows that the thermometer has 
reached its lowest temperature. The thermometers must usually 
be whirled a minute or more before this temperature is reached. 

The rate of evaporation of the water surrounding the "wet 
bulb" will vary as the movement of the air past the bulb varies, 
and for these reasons accurate results cannot be obtained un- 
less the speed of passage of the air by the bulb is rapid and uni- 
form. It is for this reason that the thermometers are whirled. 
The whirling should not be too fast, but should be carried on 
at such rate that the bulb of the thermometer will have a veloc- 

1 See U. S. Dept. of Agriculture, Weather Bureau, Bulletin No. 235, p. 5. 



374 GAS ANALYSIS 

ity of about fifteen feet per second, which with the above in- 
strument will be obtained by turning the handle C about one 
and one-half revolutions per second. 

Calculation of Results. In the calculation of results the 
following equation is employed: 

e = e 



0.000367 P (t (i + 






in which e is the absolute humidity in inches of mercury, / and /' 
are the temperatures respectively of the "dry" and "wet bulb" 
thermometers expressed in degrees Fahrenheit, P is the baro- 
metric pressure of the air in inches of mercury and e' is the maxi- 
mum tension of water vapor in inches of mercury at the tem- 
perature /' of the "wet bulb. " 

The relative humidity may then be calculated with the aid 
of the tables given in the bulletin of the Weather Bureau cited 
above. 

It would seem preferable, in scientific work, to express the 
temperatures in degrees Centigrade, and the barometric pres- 
sure in millimeters of mercury. If this be done the formula be- 
comes 

(873 + 



e = e' .000661 B(t 



873 



in which B is the barometric pressure in millimeters of mercury, 
and / and t f are the temperatures of the wet and dry bulb ther- 
mometers in degrees Centigrade. 

The absolute humidity e having thus been ascertained, the 
relative humidity is calculated by dividing this result by the maxi- 
mum tension of water vapor E possible at the temperature 
shown by the dry bulb thermometer. This result multiplied 
by 100 gives the relative humidity expressed in "degrees" or 
per cent. 

Relative humidity in e 

= - X ioo 
degrees or per cent _g 



EXAMINATION OF ATMOSPHERIC AIR 375 

The values of E at temperatures between 2 C. and + 34 C. 
will be found on p. 41 1. 

The August Psychrometer. A somewhat simpler instrument 
than the whirling psychrometer but one that is based upon the 
same principle is the August Psychrometer. It consists of two 
thermometers placed side by side on a stand. The bulb of one 
of the thermometers is covered with thin muslin that is kept 
moist by a small lamp-wick which is fastened over the muslin and 
dips into a vessel that contains water. Evaporation is allowed to 
proceed until the temperature of the wet bulb ceases to fall. 
The temperature of this thermometer, / , is then read, and also 
that of the dry thermometer, /. The absolute humidity of the 
air is then calculated with the use of the formula 

e = e k(t t'}b 

in which e is the tension corresponding to the temperature /', 
and b is the barometric pressure in millimeters, k is an empirical 
factor that varies with the speed of flow of the air past the wet 
bulb. According to the researches of Regnault, the values for k 
under different conditions are as follows : 

In small closed rooms o . ooi 28 

" large " " . . o.ooioo 

" halls with open windows . . . . . . 0.00077 

" courts . . . . . . . . . . . 0.00074 

' open air (no wind) o . 00090 

It is not always easy, however, to decide which factor should be 
used, and experience has shown that the August psychrometer 
will yield satisfactory results only when it is standardized against 
the whirling psychrometer, and the proper factor for the special 
surroundings is thus determined. 

The Hygrodeik. There is obtainable on the market a con- 
venient modification of the August psychrometer that is termed 
Lloyd's Hygrodeik. By means of a pointer and chart attached 
to this instrument, the relative humidity of the atmosphere 
may be read off with ease and celerity. 



376 GAS ANALYSIS 



Determination of Carbon Dioxide in the Atmosphere 

The deleterious effects that result from the breathing of air 
in crowded or ill-ventilated rooms have, until quite recently, 
been supposed to be due to poisonous substances exhaled from 
the lungs of the occupants. Inasmuch as it has been impossible 
to ascertain the quantity of these emanations from the lungs, 
the carbon dioxide, which is simultaneously exhaled and which 
can be accurately determined, has been regarded as a measure 
of the toxic organic substances. 

The theory is now advanced that the injurious effects arising 
from poor ventilation are due not to toxic emanations from the 
lungs, but rather "to a disturbance of the normal thermal 
relations of the body. It is a common observation that the 
depression and fatigue experienced on a hot, humid August 
day are very similar to the feelings that develop in a crowded 
' close' room. The cause is apparently the same in both cases, 
namely, interference with the normal rate of loss of body heat. 
At least three atmospheric factors may be concerned in such 
interference: high temperature of the ambient air, high mois- 
ture content and lack of air movement. Paul l kept healthy 
persons for several hours in a close cabinet until the carbon 
dioxide rose to 100 or 150 parts per thousand more than 
ten times the amount usually stated as t allowable ' but so 
long as the temperature and moisture content were kept low, 
no symptoms of illness or discomfort developed. Other experi- 
menters have reached the same result by simply having electric 
fans whirled in such an experiment cabinet. The motion these 
imparted to the air was sufficient to facilitate a normal, physio- 
logic loss of heat from the body in spite of high temperature 
and humidity. Similar cabinet experiments in which the sub- 
ject was enabled to breathe the fresh outside air through a tube, 
but was otherwise subjected to the conditions of a close room, 

1 Paul, Ztschr.f. Hyg., 49 (1905), 405. 



EXAMINATION OF ATMOSPHERIC AIR 377 

likewise showed that the symptoms attributed to 'bad ventila- 
tion ' are in nowise due to poisons excreted in the breath. The 
upshot of all such experiments is that it is not the chemical 
constitution of indoor air that is injurious, but the overheating, 
the stagnation and sometimes the moisture content." 1 

Even if this view were correct, it still remains true that the 
amount of carbon dioxide in the air of a room furnishes a means 
of judging the efficiency of the ventilation, and for this rea- 
son the accurate determination of this constituent is still of 
importance even although it should appear that the accompany- 
ing exhaled products from the lungs are not toxic in character. 

According to Benedict 2 the amount of carbon dioxide in 
air serves as quite an exact indication of the per cent of oxygen 
that is present. "For every o.oi per cent increase in the at- 
mospheric carbon dioxide, one may safely assume a correspond- 
ing decrease in the percentage of oxygen." 

Methods employed in Determination of Carbon Dioxide in 
Air. The methods that have been devised for the determina- 
tion of carbon dioxide in the atmosphere may roughly be divided 
into two classes those in which the carbon dioxide is ab- 
sorbed by a suitable solution of known strength, and the excess 
of the absorbent is determined by chemical means, and those in 
which the carbon dioxide is absorbed and the consequent de- 
crease in the volume of the sample of air is measured. 

The Hesse Method. A great number of methods of the 
first class have been proposed. Most of them aim to give ap- 
proximate results in a short space of time. These will not here 
be considered. Of the other and more accurate methods, that 
original with Saussure and improved by Pettenkofer and later 
by Hesse 3 has proven itself to be one of the most satisfactory. 

1 Jour. Amer. Med. Association, September 16, 1911, Vol. 57, No. 12, p. 980. 

2 The Composition of the Atmosphere. Publication No. 166 of the Carnegie Institu- 
tion of Washington, 1912, p. 115. 

3 Anleitung zur Bestimmitng der Kohlensaure in der Luff, nebst einer Beschreibung 
des hierzu nothigen Apparates; Eulenberg's Vierteljahrsschr. f. gerichtl. Medicin und 
ojfentl. Sanitatswesen, N. F. 31, 2. 



378 



GAS ANALYSIS 



In this procedure the carbon dioxide in a known volume of 
air is absorbed by a solution of barium hydroxide of known 
strength and the amount of barium hydroxide that has not 
combined with carbon dioxide is then determined oy titration 
with a solution of oxalic acid, phenolphthaleiri being used as 
indicator. 

Solutions used in the Hesse Method. The stock solutions 
needed in the analysis are the following 

(i) One kilogram of barium hydroxide and 50 grams of barium 
chloride are added to about five liters of distilled water con- 
tained in a large bottle. As the clear supernatant liquid is 
used, it is replaced by water so long as there is solid material 
in excess. 

(2) A dilute solution of barium 
hydroxide that is prepared by 
adding about 30 cc. of the con- 
centrated solution No. i to one 
liter of water. This is placed in 
a bottle B (Fig. 104), provided 
with a small absorption bottle C 
that contains potassium hydrox- 
ide which frees the entering air 
from carbon dioxide. This dilute 
solution may also be prepared 
directly by dissolving 1.7 grams 
of a mixture of barium hydroxide 
and barium chloride (20:1) in one 
liter of distilled water. Phenol- 

phthalein is added to this solution until it has a faint but dis- 
tinct pink color. 

(3) A solution of oxalic acid that contains 5.6325 grams of 
crystallized oxalic acid in one liter of water. One cc. of this 
solution is equivalent to one cc. of carbon dioxide. 

(4) A solution of phenolphthalein that contains one part 
of the substance dissolved in 250 parts of alcohol. 




FIG. 104 



EXAMINATION OF ATMOSPHERIC AIR 379 

Collection of Samples of Air. The samples of air are col- 
lected in thick- walled Erlenmeyer flasks of 100, 200, 300,' 400, 
500 cc. capacity that are supplied with tightly fitting, double- 
bore rubber stoppers. The point to which the rubber stopper 
reaches into the neck of the flask is marked on each flask, and 
the capacity of the flask up to this line is determined and is 
marked on the glass. Pieces of glass rod from 3 to 5 cm. long are 
used to close the openings in the stoppers. These rods should 
be well rounded at the lower ends and should be widened at the 
upper end by heating them in the flame of a blast lamp and 
pressing them on a cold surface. Further apparatus that is 
needed in the work comprises a pipette of 10 cc. capacity, and 
a burette with glass stopcock. The burette has a capacity of 

from 10 to 15 cc., is graduated in cc., and has a tip about 

8 cm. long. 

Manipulation. Each determination of carbon dioxide by 
Hesse's method is in reality a double one, two determinations 
of the constituent being made in samples of air of different vol- 
umes. These samples are collected in two of the Erlenmeyer 
flasks above described, the two flasks being of different capacity 
and the sizes of the flasks that are used depending upon whether 
a smaller or a larger amount of carbon dioxide in the air is to be 
expected. The samples of air are collected by completely filling 
the flasks, at the place where the air is to be examined, with dis- 
tilled water that has the same temperature as the surrounding 
air, and then pouring out the water and immediately inserting 
the rubber stoppers in the necks of the flasks, the holes of the 
stoppers being closed with the glass plugs. In this operation care 
should be exercised that the flask is not warmed by the hand and 
that no air exhaled by the operator enters the flask. The flasks 
are transferred to the laboratory and the carbon dioxide in 
each of the two samples is then determined. The glass plug is 
removed from the end of the rubber tube (Fig. 104), the tip 
of the 10 cc. pipette is inserted into the end of the tube, the 



380 GAS ANALYSIS 

pinchcock is opened and some of the solution of barium hy- 
droxide is drawn up into the pipette. The pipette is rinsed with 
this solution which is then driven out of the pipette. The pipette 
is then reinserted in the end of the rubber tube and barium hy- 
droxide is drawn up to the zero mark whereupon the pinchcock 
is closed. One of the glass plugs in the stopper of one of the 
Erlenmeyer sample flasks is withdrawn and the tip of the pi- 
pette is inserted into the flask through this opening. The solu- 
tion of barium hydroxide is then run into the flask, the air that 
is displaced by the solution being allowed to escape by moment- 
arily removing the glass plug in the other hole of the stopper. 
The last drops of barium hydroxide in the pipette are driven out 
by closing the upper end of the pipette with the finger, and 
warming the wider portion of the pipette with the hand. The 
pipette is then withdrawn from the flask and the stopper is 
closed with the glass plug. This procedure is repeated with 
the other sample of air contained in the second flask. The 
closed flasks are allowed to stand for from fifteen to twenty 
minutes with occasional shaking. For the complete absorption 
of the carbon dioxide in the sample of air in the flask it is essen- 
tial that the barium hydroxide be present in so large excess that 
not more than one-fifth of it enters into the reaction. If the 
sample of air is quite large, or if the carbon dioxide contained 
is high, 20 or even 25 cc. of the solution of barium hydroxide 
should be used. 

While the absorption of carbon dioxide in the flask is pro- 
ceeding, the strength of the solution of barium hydroxide is 
determined by filling the burette to the mark with the dilute, 
standardized solution of oxalic acid (0.56325 gram per liter), 
inserting the tip of the burette through one opening of a 
two-hole rubber stopper, placing the stopper in the neck of a 
100 cc. Erlenmeyer flask in the manner shown in Fig. 105, 
and then running into the flask a volume of the solution 
of oxalic acid almost sufficient to neutralize 10 cc. of the solu- 
tion of barium hydroxide. 10 cc. of this latter solution is 



EXAMINATION OF ATMOSPHERIC AIR 



38! 



then introduced into the flask in the manner above described 
and the oxalic acid is then carefully added until the pink color 
of the indicator just disappears. This color will frequently 
reappear on standing because of the presence of traces of 
potassium hydroxide or sodium hy- 
droxide in the solution. 

The excess of barium hydroxide in 
the two sample flasks is then titrated 
by filling the burette to the mark 
with the standardized, dilute oxalic 
acid, inserting the tip of the burette 
through one of the openings of the 
stopper and running in the oxalic 
acid at first rapidly, and then to- 
ward the end of the reaction drop 
by drop. The increase of pressure in 
the flask is relieved from time to 
time by momentarily lifting the glass 
plug in the other opening of the 
stopper. As before, the end point of 
the reaction is the first disappearance 
of the pink color. 

Calculation of Results. The 
temperature and the prevailing at- 
mospheric pressure are then read. FIG. 105 

10 cc. is deducted from the volume of 

each sample flask to allow for the volume of air displaced by 
the solution of barium hydroxide that has been introduced, 
and the remaining volume is corrected to standard conditions 
of temperature and pressure. This result represents the vol- 
ume of the air sample in the flask. The number of cubic cen- 
timeters of the solution of oxalic acid required to neutralize 
the excess of the barium hydroxide is deducted from the volume 
of oxalic acid required to neutralize 10 cc. of the barium hy- 
droxide. Representing this difference by n, the amount of carbon 




382 GAS ANALYSIS 

dioxide in the sample may be calculated by means of the fol- 
lowing proportion: 

: volume of air sample taken = x : 10,000 

in which x represents the parts of carbon dioxide per 10,000 of air. 

The Pettersson-Palmqvist Method. Of the second type 
of methods for the determination of small percentages of car- 
bon dioxide, that devised by Pettersson and Palmqvist 1 is one 
of the most satisfactory and accurate. 

The apparatus that they designed permits of the measure- 
ment of as small a volume of air as 25 cc. with an accuracy of 
one part in 10,000, and avoids the necessity of making cor- 
rections for variations in pressure and temperature. This is 
made possible by the use of a compensating tube that is filled 
with air and that stands in communication with one side of a 
manometer tube, the burette in which the air is measured being 
attached to the other side of the manometer. Both compensat- 
ing tube and burette, which are of nearly the same capacity, 
stand in a vessel of water. If the temperature of this sur- 
rounding water changes during the experiment the effect upon 
the volume of air in each tube is the same. 

If, now, the two tubes are always brought into communication 
with the manometer when the air in the burette is measured, it 
follows that if the liquid in the manometer is brought to the 
same point in each case, the air in the burette is measured under 
exactly the same conditions of pressure and temperature as pre- 
vail in the compensating tube, and since the inclosed volume 
of air in the compensating tube, which is of course unaffected by 
changes in barometric pressure, is at each measurement brought 
back to the volume corresponding to the original conditions of 
temperature and pressure, the air in the burette is similarly 
affected, and for this reason no corrections for changes in tem- 
perature and pressure are necessary. 

The apparatus of Pettersson and Palmqvist, with slight 

1 Berichte der deutschen chemischen Gesellschaft, 20 (1887), 2129. 



EXAMINATION OF ATMOSPHERIC AIR 383 

modifications introduced by the author, is shown in Fig. 106. 
The air is measured in the burette A which contains 25 cc. from 
a mark on its upper capillary tube down to the zero point at 
the lower end of the capillary S. This capillary is calibrated 
in divisions each of which amounts to i ,ooo part of the total 
volume of the burette. The somewhat wider capillary T is 
calibrated in divisions that represent 1>0 1 00 part of the vol- 
ume of the burette. The lower end of T is connected by means 
of a piece of rubber tubing with the glass stopcock V; this rubber 
tube can be compressed by turning the screw N and forcing down 
upon the tube a flat metal plate attached to the end of the screw. 
The lower tube of the stopcock V is joined to the level-bulb E 
by a piece of enamelled rubber tubing. At the upper end of the 
burette A are three branch capillary tubes. The one to the left 
in the drawing is provided with the two-way stopcock / through 
which the sample of air is drawn into the apparatus either di- 
rectly from the outer atmosphere through P or through the coil 
of copper tubing H and the glass tube /. At the right, A is con- 
nected through the stopcock L with an Orsat gas pipette B 
that contains glass tubes and is charged with a solution of potas- 
sium hydroxide for the absorption of carbon dioxide. The other 
branch capillary tube joins A through the stopcock K to the 
manometer M which may be brought into communication with 
the outer air by opening the stopcocks F and G. The other 
end of M is connected by the rubber tube D to the glass com- 
pensating tube C. The burette A, the pipette B, the compensat- 
ing tube C and the coil of copper tube H as well as the capillary 
tubes S and T are surrounded by water that is contained in the 
wide glass cylinder and in the jacket tube around the lower 
capillaries. The whole apparatus is mounted on a board about 
90 cm. high and 30 cm. wide which is itself set into a square 
wooden base. The apparatus can be covered by a wooden box 
that slides down over it and that is held in place by the screws 
shown at the top of the board. This cover does not appear in 
the figure. 



GAS ANALYSIS 




FIG. 106 



EXAMINATION OF ATMOSPHERIC AIR 385 

The manometer M contains a drop of petroleum in which 
azobenzene is dissolved and there is etched upon the surface of 
the tube a scale by means of which the position of the drop 
may be read. 

The coil of copper tube H has been added to the original 
Pettersson-Palmqvist apparatus because it has been found, in 
determining the carbon dioxide in the air of rooms that are or 
recently have been occupied, that it takes several minutes for 
the sample of warm air from the upper part of the room to fall 
to the temperature of the water that surrounds A. This is 
shown by the side movement of the drop of liquid in the manom- 
eter after the sample has been measured. If, however, instead 
of drawing the air directly into A through P it is caused to pass 
through the coil H, which is about 80 cm. long, 3 mm. internal 
diameter, and 5 mm. external diameter, the entering sample of 
air is rapidly cooled (or warmed) to the temperature of the sur- 
rounding water. 

It has oftentimes been noticed that the change in the volume 
of the sample of air in A that is caused by its rising or falling 
to the temperature of the surrounding water, produces a greater 
movement of the manometer liquid than would result from the 
removal of the carbon dioxide in the sample. 

In making a determination of carbon dioxide with this ap- 
paratus, clean mercury is poured into the level-bulb E in an 
amount sufficient to fill the connecting tubes and the burette A . 
The stopcock J is turned to such position that A communicates 
with P, and one drop of water is introduced into the end of the 
tube and is drawn over into A. The absorption tube B is then 
filled with a 33 per cent solution of potassium hydroxide. The 
apparatus is now transferred to the place where the air or other 
gas mixture is to be examined. The glass cylinder surrounding 
the absorption and measuring tubes is filled with water of the 
temperature of the surrounding air. Stopcocks V and / are 
now opened, the level-bulb E is raised, and mercury is driven 
nearly to the top of the burette A. /is now closed, the level- 



386 GAS ANALYSIS 

bulb E is lowered, the stopcock L is carefully opened, and the 
solution of potassium hydroxide in the absorption tube B is 
drawn up to a mark on the stem at which this solution must 
always stand when measurements are made. L is then closed, 
J is turned to such position that A communicates with P and 
the mercury in the burette A is raised until it stands at the mark 
on the capillary tube above the burette. The level-bulb E is 
now slowly lowered, and air is drawn into A until the mercury 
falls to about the point T. J is then turned to such position 
that A communicates with the coil H and the level-bulb is now 
raised and this first sample of air is driven out through the 
outlet 7. A second sample is now drawn in through / and H 
by lowering E, the mercury being allowed to fall to a point 
slightly below the zero mark on the capillary tube S. The stop- 
cocks / and V are then closed and the rubber tube at the bottom 
of the measuring burette is compressed by turning the screw 
N until the mercury stands exactly at the zero mark of the 
tube S. The stopcock / is then opened for a moment to bring 
the sample in the burette A to atmospheric pressure. The stop- 
cocks F and G are next carefully opened to bring the air upon 
both sides of the manometer and in the compensating tube C to 
atmospheric pressure. In this operation care must be exercised 
to avoid driving out the drop of liquid from the tube M . F and 
G are now closed, the stopcock K is carefully opened, and the 
position of the drop of liquid in the manometer M is noted. 
The stopcock K is then closed, the stopcocks V and then L are 
opened, and the sample of air is driven over into the absorption 
pipette B where it is allowed to remain for one minute in contact 
with the absorbent. The level-bulb E is then lowered and the 
solution of potassium hydroxide in B is drawn up again to the 
mark, whereupon L is closed. The residual gas in the burette A 
is now brought approximately to atmospheric pressure by proper 
adjustment of the height of the level-bulb E and the stopcock V 
is then closed. K is opened and the drop of liquid in the manom- 
eter M is brought to its original position by turning the com- 



EXAMINATION OF ATMOSPHERIC AIR 387 

pression screw N. The final volume of the gas is now read off 
on the capillary tube S and the difference between this reading 
and the reading of the initial volume, expressed in divisions on 
this tube, corresponds to the parts of carbon dioxide per 10,000 
in the sample of air under examination. 

If the carbon dioxide in the sample is higher than 0.4 per cent, 
the wider calibrated capillary tube T is employed in making 
the measurements, one division on this tube corresponding to 
one part of carbon dioxide per 1,000 parts of air. 

A serious objection to the Pettersson-Palmqvist apparatus 
is its size and weight. It is also quite difficult to replace any of 
the glass parts that may be broken. Modifications of the ap- 
paratus, with a view to making it more easily portable, have 
been proposed by Bleier l and Rogers, but in the opinion of the 
author, the objections to the original form are most satisfac- 
torily met by the device described by Anderson 2 and shown in 
Fig. 107. 

Anderson's Modification of the Pettersson-Palmqvist 
Apparatus. The gas is measured in the burette A and the 
change in volume of the sample that results when the carbon 
dioxide is absorbed is read upon the capillary S. This bent 
capillary tube passes through a stopper and is joined to the 
stopcock V by a piece of rubber tubing. This rubber tube 
passes under the compression screw N by means of which the 
fine adjustment of the mercury in the capillary tube 5 1 is effected. 
The other side of the stopcock V is connected with the level- 
bulb E by a piece of enamelled 'rubber tubing. A solution of 
potassium hydroxide for the absorption of carbon dioxide is 
contained in the pipette B, C is the compensating tube, and M 
the manometer. By means of the three-way stopcock / the 
sample of air may be drawn through the coil of copper tubing 
H, H', H". The compensating tube C may, by means of the 
three-way stopcock F, be brought into communication with the 

1 Z.f. Hygiene, 27 (1898), in. 

2 J. Amer. Chem. Soc. 35 (1913), 162. 



3 88 



GAS ANALYSIS 




FIG. 107 



EXAMINATION OF ATMOSPHERIC AIR 389 

atmosphere through the side arm whenever necessary. The 
liquid index in the manometer is introduced through the stop- 
cock G. 

The burette, pipette, compensating tube, and the copper 
coil are immersed in water that is contained in a glass cell of 
rectangular cross section, and that is provided at the lower side 
with a neck like the neck of a bottle into which the rubber stopper 
shown in the figure is tightly inserted. In addition to the capillary 
tube 6* there passes through this rubber stopper a short piece of 
glass tubing through which the water in the cell may be run 
off. The glass parts of the apparatus in the cell are fastened 
to a sliding board DD above the cell. If the rubber stopper 
passing through the neck of the cell is loosened, and the rub- 
ber tube is slipped off from the lower end of S, the appara- 
tus may be lifted from the case by raising the board to which 
it is attached. Ready access to all parts of the apparatus 
is thus easily attained, and the cleaning and repairing of the 
different portions is rendered easy. Furthermore, the position 
of the board may be adjusted, within certain limits, by means 
of the screw X, a detail that is of importance in mounting new 
glass parts of slightly different dimensions from those of the 
older parts. The case, Fig. 108, is provided with a removable 
front and top and with a pane of glass at the the back to illumi- 
nate the apparatus when it stands between the operator and 
the window. 

This form of the Pettersson-Palmqvist apparatus devised 
by Anderson is only 42 cm. high whereas the original apparatus 
has a height of 90 cm. Its small size and the ease with which 
it may be manipulated renders it distinctly superior to the 
original form. 

Before the apparatus is put into use the glass parts should, if 
necessary, be thoroughly cleaned, and the stopcocks should be 
carefully lubricated. In preparing the apparatus for use about 
30 cc. of distilled mercury is poured into the level-bulb E and a 
small quantity of water is introduced into the burette through 



GAS ANALYSIS 




FIG. 108 



EXAMINATION OF ATMOSPHERIC AIR 391 

the opening T directly above the stopcock /. This is done by 
covering the end of this capillary tube with a film of water and 
drawing an amount of the liquid sufficient to form a column from 
3 to 5 mm. long in the capillary tube into the burette by lowering 
the level-bulb. 

The drop of liquid that is used in the manometer (petroleum 
in which azobenzene has been dissolved) is introduced into M by 
filling the burette A nearly to the top with mercury with the 
stopcocks K and G open, and then closing stopcock V and screw- 
ing down the compression screw N. A small amount of the 
manometer liquid is now brought upon the end of the capillary 
tube upon stopcock G, and an amount of the liquid sufficient 
to occupy a length of from 3 to 5 mm. in M is drawn into the 
capillary as far as the branch tube below stopcock G by turning 
back the compression screw N. Stopcock G is then closed, F is 
opened and the compression screw N is again turned down upon 
the rubber tube, and the liquid is, in this manner, forced into 
the manometer tube M. 

The pipette B is filled with a solution of potassium hydroxide 
that is prepared by dissolving one part of potassium hydroxide 
in two parts of water. This solution is drawn up to the mark 
on the capillary by lowering the level-bulb E, and stopcock L 
is then closed. 

Before proceeding with the determination of the carbon 
dioxide in the air of a room, the apparatus should be allowed to 
stand long enough in the room to insure equilibrium between 
the temperature of the water in the water jacket and the tem- 
perature of the air in the room. The air in the manometer tube 
M and in the compensating tube C should be brought to atmos- 
pheric pressure by opening the stopcocks F and G. During a 
determination the apparatus should not stand in direct sunlight 
or in a draft of air. 

The actual determination of carbon dioxide is carried on 
as follows : Turn stopcock / to such position that the bu- 
rette A communicates with the outer air through the tube T. 



392 GAS ANALYSIS 

Fill the burette A with mercury by opening stopcock V and 
raising the level-bulb E. Turn stopcock / to such position 
that the burette A communicates with the copper tube H, and 
draw air into A through H by lowering the level-bulb E. Inas- 
much as this sample is mixed with air that was already present 
in the connecting tubes and the copper tube H, it is driven out 
through T by turning the stopcock / into the proper position 
and raising the level-bulb. Stopcock / is then turned back so 
that A communicates with H. The level-bulb E is again lowered 
and the sample of air is drawn into the burette A until the mer- 
cury in the burette falls slightly below the zero mark on the 
capillary tube S. Stopcock V is then closed and the compression 
screw N is turned until the mercury stands exactly at the zero 
mark. Allow stopcock / to remain open for a few moments to 
allow the air in the burette to assume atmospheric pressure and 
then close /. Open stopcock K carefully, and read the position 
of the liquid in the manometer M. Then close stopcock K. 

To remove the carbon dioxide in the sample, open stopcock V 
and then stopcock L and drive the gas over into the pipette B. 
When the mercury nearly reaches the stopcock L, close that 
stopcock and leave the gas in contact with the potassium hy- 
droxide for one minute. Then lower the level-bulb, open stop- 
cock L, draw the gas back into the burette, and when the solution 
of potassium hydroxide rises to the mark on the capillary close 
stopcock L. Bring the mercury approximately to the zero 
mark in the capillary S by raising or lowering level-bulb E, close 
the stopcock V and then turn the compression screw N until the 
mercury in the capillary tube S stands at such a point above 
the zero mark as will correspond approximately to the percentage 
of carbon dioxide in the air under examination. Then open 
stopcock K and turn N until the liquid in the manometer stands 
at the position that is occupied before the absorption was made. 
The reading of the mercury in the capillary tube S now gives 
directly the amount of carbon dioxide in the sample of air ex- 
pressed in parts per 10,000. 



CHAPTER XIX 

THE ANALYSIS OF SALTPETER AND NITRIC ACID ES- 
TERS (NITROGLYCERINE, GUN-COTTON) WITH THE 
NITROMETER 

Walter Crum 1 observed that the higher oxides of nitrogen 
are completely reduced to nitric oxide when absorbed in sul- 
phuric acid and then shaken with mercury. John Watts 2 
and Georg Lunge 3 developed this method still further, and 
the latter constructed an apparatus therefor which he termed 
a nitrometer. Hempel utilized 4 the reaction in the decomposi- 
tion of the nitric acid esters, and in particular in the determina- 
tion of the nitroglycerine in dynamite. For this work he designed 
a special nitrometer which is also admirably adapted to the eval- 
uation of saltpeter. In its original form, however, the Hempel 
nitrometer is open to objection because the rubber stopper that 
carries the sample tube is kept in place only with difficulty, and 
because further of the awkwardness of cleaning the apparatus 
after a determination has been made. The author has sought to 
remedy these defects by giving to the nitrometer the form shown 
in Fig. 109. 

The Nitrometer. The evolution cylinder C is provided at 
the lower end with the double-bore stopcock T and the side 
arm R. The stopcock 5, also of double bore, is attached to the 
upper end of the cylinder by the carefully ground joint J and 
is held in place by rubber bands slipped over the small glass 
hooks above and below the joint. K is a capillary tube which 
serves to connect the nitrometer with the gas burette in which 

1 Philosoph. Mag. 30 (1847), 426. 

2 Chemical News, 37 (1878), 45. 

3 Berichte der deutschen chemischen Gesettschaft, II (1878), 434. 

4 Zeitschrijt fur analyt. Chemie, 20 (1881), 82. 

393 



394 



GAS ANALYSIS 



the evolved nitric oxide is measured. Lisa, level-bulb that is 
joined to one arm of the stopcock T by a piece of enamelled 
rubber tubing. 

The manipulation of the apparatus in the evaluation of 
saltpeter or other nitrate is as follows : Place the evolution 

cylinder C in a large clamp and 
attach it to an iron stand in an up- 
right position. Place the level- 
bulb L in a split ring that is also 
attached to the rod of the iron 
stand and introduce into L an 
amount of mercury sufficient to 
fill the evolution cylinder C, the 
side arm R, and the rubber tube 
joining L and C. Remove the 
stopcock S from the top of the 
cylinder C, turn the stopcock T 
into such position that L and C 
will be in communication, and fill 
the evolution cylinder C with mer- 
cury to a point about 5 cm. below 
the top of the tube /. Introduce 
into the upper end of C through 
the open tube / about 5 cc. of a 
solution of the nitrate to be ana- 
lyzed, running in the solution from 
the small burette B, which is calibrated in tenths of a cubic 
centimeter and can easily be read to fiftieths. Place the stop- 
cock S upon / and fasten it in position by rubber bands at- 
tached to the small hooks on either side of the joint. Raise 
the level-bulb until the top of the solution in C just reaches 
the lower side of the stopcock S and then close 6 1 and T. 
Lower the level-bulb L and then carefully open the stopcock 
T until the mercury in the side arm R falls to about the begin- 
ning of the bend in that tube. 




ANALYSIS OF SALTPETER AND NITRIC ACID 395 

Introduce a measured amount (about 20 cc.) of concentrated 
sulphuric acid into the upper open end of R. Remove C from 
the clamp and hold it in an inclined position, with the tube R 
on the upper side, at such height that the mercury in R stands 
at the same level as that in the level-bulb L. Turn the stop- 
cock T to such position that L communicates with C and then 
slowly raise C (still holding it in an inclined position) until 
all but about 5 cc. of the sulphuric acid has been drawn into 
the evolution cylinder C. Now lower C until the mercury rises 
to about the middle of the tube R and then close the stopcock T. 
Shake the cylinder C to insure intimate mixing of the sulphuric 
acid with the solution of the nitrate. As the reaction proceeds 
the evolution of gas tends to force the mercury upwards in the 
side arm R. The level of the mercury in this arm is kept ap- 
proximately the same during the reaction by opening the stop- 
cock T from time to time and allowing the mercury to flow back 
into the level-bulb L. The shaking of the evolution cylinder C 
is continued until, with the stopcock T closed, no further rise 
of the mercury in R is observed. The reaction is then complete. 

C is now again clamped in a vertical position and the capillary 
tube K is attached by means of a small L-shaped piece of capil- 
lary tubing to a Hempel gas burette that contains mercury as 
the confining liquid and into which a very little water has been 
introduced. The stopcock S is then turned to such position as 
to connect K with the outlet M , and the level -tube of the burette 
is raised until the capillary tube K is completely filled with 
mercury. S is now turned through 180 so that the cylinder C 
communicates with the tube K. T is then turned to such posi- 
tion that L and C are connected, and the evolved gas is drawn 
over into the burette, the sulphuric acid in the nitrometer being 
allowed to follow the gas until it almost reaches the end of the 
capillary tube K. The stopcock S is then closed, the pinchcock 
at the top of the burette is also closed and the nitric oxide in the 
burette is measured in the usual manner, due allowance being 
made for the tension of water vapor. 



396 GAS ANALYSIS 

After a determination has been made, the nitrometer is 
cleaned by lowering the level-bulb, opening the stopcocks ,S 
and T and allowing the clean mercury to flow back into the 
bulb L. The stopcock T is then turned into the position shown 
in the figure and the dirty mercury, mercurous sulphate, and 
sulphuric acid are allowed to run out through the tube N into a 
beaker. The stopcock 6* is next slipped off from the upper end of 
the cylinder C and the side arm R as well as the wide tube of the 
stopcock 5* are thoroughly rinsed with water and are then dried. 

In calculating the results of the analysis allowance must be 
made for the solubility of nitric oxide in sulphuric acid. 15 cc. 
of sulphuric acid will dissolve about 0.2 cc. of nitric oxide. 

The purity of the nitric oxide that is evolved may be ascer- 
tained by passing the gas, after it has been measured in the 
burette, into a double gas pipette for liquid reagents that con- 
tains in the first two bulbs a solution of a ferrous salt, and in the 
last two, water. The analytical absorbing power of a saturated 
solution of ferrous chloride is 14, and of ferrous sulphate about 4. 

In the evaluation of saltpeter the sample should be dissolved 
in a little water and 5 cc. of this solution is used in the analysis. 
The concentration of this solution should be such that about 
75 cc. of nitric oxide will be evolved. 

In the analysis of solid material a weighed sample of the 
substance is introduced into the upper open end of the evolution 
cylinder C. The sample is moistened with a little water, the 
stopcock 6* is then placed in position and fastened with rubber 
bands, mercury is driven up to the lower side of the stopcock S, 
and the further analysis is then carried out in the manner above 
described. 

In the analysis of gun-cotton Hagen first shakes the sample 
with concentrated sulphuric acid in the evolution cylinder C for 
three minutes, and then when the gun-cotton is dissolved, he 
heats C by holding it in an inclined position over a Bunsen 
burner, and continues the shaking of C as long as evolution 
of gas is observed. 



CHAPTER XX 
THE LUNGE NITROMETER 

The nitrometer of Lunge 1 was originally designed for the 
evaluation of nitrates. For this specific purpose it is inferior to 
the nitrometer described in Chapter XIX, because the nitric 
oxide is evolved in the tube in which the gas volume is finally 
read, and the foaming of the acid renders difficult the accurate 
reading of the height of the confining liquid. 

A modified form of his nitrometer which Lunge later described 2 
under the name of a ureometer, but which is generally known 
under the name of the Lunge nitrometer, is an instrument of 
wide application in gas-volumetric analysis. 3 

The Lunge Nitrometer. The instrument (Fig. no) con- 
sists of a gas burette A, a level- tube B, and an evolution flask C. 
The burette has a capacity of more than 100 cc. It is provided 
at the upper end with a two-bore stopcock, and is graduated 
from the stopcock downward in -J- cc. 

One of the two tubes of the stopcock is a short upright 
capillary tube of the usual diameter: the- other tube is some- 
what larger and is bent over until it points nearly downward. 
To it the evolution flask C is joined by a short piece of rubber 
tubing, the ends of the glass tubes being brought nearly together. 

The evolution flask C usually has a capacity of about 100 cc. 
A short tube, open at the top, is fused to the bottom of the flask. 
A soft, one-hole rubber stopper carrying a short glass tube 
is inserted in the neck of C. 

1 Berichte der deutschen chemischen Gesellschqft, 1 1 (1878), 434; ibid, 21 (1888), 376. 

2 Berichte der deutschen chemischen Gesellschaft, 18 (1885), 2030. 

3 See A. H. Allen, /. Soc. Chem. Ind. 4 (1885), 178; Lunge, Chemische Industrie, 
1885, i6i;J.Ss. Chem. Ind., g (1890), 21. 

397 



398 



GAS ANALYSIS 



Manipulation of the Lunge Nitrometer. In making a de- 
termination with the nitrometer, water or mercury is poured 
into the open end of the level-tube B, the stopcock D is 

opened, and the confining 
liquid is allowed to rise nearly 
to the stopcock which is then 
closed. The reacting sub- 
stances are now placed in the 
evolution flask C, one in the 
outer space, the other in the 
tube. The short rubber tube 
carrying the stopper of C is 
slipped over the end of the 
bent tube of D, and the rub- 
ber stopper is then tightly 
inserted into the neck of the 
evolution flask. In doing 
this the neck of the evolution 
flask should be grasped be- 
tween the thumb and fingers 
of one hand and the stopper 
be pushed into the neck of 
the flask with the other hand. 
The body of the flask itself 
should not be touched by the 
hand during the operation 
because this would warm the 
air in the flask and would 
cause error in the next ad- 
justment. The air in C is 
slightly compressed by the 
insertion of the stopper. It 
is brought to atmospheric 
pressure by turning the stop- 




FIG. no 



cock D so that the evolution 



THE LUNGE NITROMETER 399 

flask connects with the burette, and then bringing the confining 
liquid in the level-tube to the same height as that in the burette. 
The air in the evolution flask is now at atmospheric pressure. 
The stopcock D is turned through 180 while the tubes are in 
this position, and the level-tube is then raised until all of the 
air in the burette is driven out through the open capillary tube 
of the stopcock. The stopcock is turned to join A to C, and 
the substances in the evolution flask C are then brought to- 
gether by taking hold of the rubber stopper of the flask and tip- 
ping it. The flask itself should not be touched with the hand. 
The reaction is allowed to proceed to completion, the flask being 
occasionally gently shaken. The gas that is set free passes 
over into the burette. The pressure thus caused is relieved from 
time to time by lowering the level-tube. When the evolution 
of gas has ceased, the confining liquid in the burette and level- 
tube is brought to the same height, and the volume of gas in the 
burette is read off. 1 The thermometer and barometer are read 
and the gas volume is corrected to standard conditions. The 
necessity for this correction may be avoided by using the Lunge 
gas volumeter (see p. 37) in place of the nitrometer. 

As illustrative of the many and various gas volumetric de- 
terminations that may be made with the Lunge nitrometer 
(or with the Lunge gas volumeter) the standardization of po- 
tassium permanganate, the determination, of the active oxygen 
in hydrogen dioxide, the determination of the available chlorine 
in " chloride of lime," the evaluation of pyrolusite, and the de- 
termination of carbon dioxide in sodium carbonate will here be 
described. 

The nitrometer should be thoroughly rinsed with distilled 
water before a determination is begun, and the evolution flask 
should be carefully cleaned and dried. The apparatus should 

1 If the heat of reaction of the substances in the evolution flask is appreciable, a 
beaker containing water of the temperature of the room should be brought up under 
the flask after the reaction is complete and the flask should be allowed to stand im- 
mersed in the water for a period of five minutes before the volume of gas in the 
burette is measured. 



400 GAS ANALYSIS 

stand in a room of even temperature and should be protected 
from direct sunlight and drafts of air. The manipulation gen- 
eral to all of the various determinations has already been de- 
scribed above. 

The Standardization of Potassium Permanganate. A 
solution of potassium permanganate that is acidulated with 
sulphuric acid reacts upon hydrogen dioxide in accordance with 
the equation 

2 KMnO 4 + 3 H 2 SO 4 + 5 H 2 2 = 
K 2 SO 4 + 2 MnSO 4 + 8 H 2 O + 5 2 . 

From this it appears that 

80 parts by weight of oxygen is equivalent to 158.03 parts 
by weight of KMnO 4 . 

Since one cc. of oxygen, under standard conditions, weighs 
0.00143 ram j each cubic centimeter of evolved oxygen, reduced 
to standard conditions, is equivalent to 0.0028247 gram of 
KMnO 4 . 

If the solution of potassium permanganate is approximately 
decinormal in strength, 25 cc. of the solution is placed in the 
outer compartment of the evolution flask, and 5 cc. of normal 
sulphuric acid is added to it. About 5 cc. of a 3% solution 
of hydrogen dioxide is then placed in the inner tube of the 
flask. 

The apparatus is now connected up, the air in the evolution 
flask is brought to atmospheric pressure, the stopcock of the 
burette is turned so that the flask communicates with the bu- 
rette, and the evolution flask is then tipped and the hydrogen 
dioxide is slowly run out into the solution of potassium perman- 
ganate, the evolution bottle being constantly shaken. The 
level-tube is lowered from time to time to keep the gas in the 
burette at approximately atmospheric pressure. After the evolu- 
tion of the oxygen has ceased, the gas is measured and is re- 
duced to standard conditions. The solution in the evolution 
flask should be colorless after the reaction has taken place. If 



THE LUNGE NITROMETER 401 

it should still show the color of potassium permanganate, too 
little hydrogen dioxide has been used. If 25 cc. of the solution of 
potassium permanganate has been used in the determination, 
the grams of KMnCU per liter of solution is calculated as fol- 
lows: 

25 : 100 = cc. O 2 X 0.0028247: grams KMnO 4 per liter. 

The Determination of Active Oxygen in Hydrogen 
Dioxide. The reaction between acidulated potassium per- 
manganate and hydrogen dioxide that has just been discussed 
is utilized in this determination also. 

A saturated solution of potassium permanganate is employed, 
and an amount of this solution (usually about 10 cc.) more than 
sufficient to convert all of the sample of hydrogen dioxide into 
water and oxygen is placed in the inner tube of the evolution 
flask. 

If commercial hydrogen dioxide of the usual strength (about 
3 per cent) is under examination, it must first be diluted. 10 cc. 
of the solution is run into a 100 cc. measuring flask from a pipette 
or burette, and the flask is then filled to the mark and is shaken. 
10 cc. of this diluted solution of hydrogen dioxide and 20 cc. of 
dilute (normal) sulphuric acid are placed in the outer space of 
the evolution flask. The reaction is now effected in the usual 
manner. The solution in the evolution ilask must show the 
color of potassium permanganate after the evolution of oxygen 
has ceased. If the liquid is colorless, it indicates that too little 
potassium permanganate has been used, and that the hydro- 
gen dioxide has not been completely decomposed. 

The results are calculated in the manner described under the 
preceding determination, due allowance being made for the 
dilution of the hydrogen dioxide. 

The Determination of the Available Chlorine in " Chloride 
of Lime." Chloride of lime acts upon hydrogen dioxide as 
follows: 

CaOCl 2 + H 2 2 = CaCl 2 + H 2 O + O 2 



402 GAS ANALYSIS 

Each molecule of oxygen evolved is equivalent to a molecule 
of available chlorine in the bleaching powder, or 

i cc. O 2 = i cc. C1 2 = 0.003166 gram chlorine. 

The calculation of the result of the analysis is simplified if a 
sample of bleaching powder of exactly 0.3166 gram is used, 
for then 

i cc. oxygen = i per cent available chlorine. 

7.917 grams of the sample of chloride of lime is placed in a 
250 cc. measuring flask which is then filled up to the mark and 
thoroughly shaken. 10 cc. of the resulting turbid bleach solu- 
tion, which will contain 0.3166 gram of the chloride of lime, is 
drawn up into a pipette and is run into the outer compartment 
of the evolution flask. The measuring flask should be vigor- 
ously shaken just before the sample is drawn off into the 
pipette. 

About six cc. of a solution of hydrogen dioxicle containing 
approximately 1.5 per cent H 2 O 2 is introduced into the inner 
tube of the flask, and the determination is then carried out in 
the usual manner. 

The evolved oxygen is reduced to standard conditions. Each 
cubic centimeter of the gas is equivalent to one per cent of avail- 
able chlorine in the chloride of lime. 

The Evaluation of Pyrolusite. Manganese dioxide reacts 
with hydrogen dioxide in the presence of sulphuric acid in ac- 
cordance with the equation 

MnO 2 + H 2 O 2 + H 2 SO 4 = MnSO 4 + 2 H 2 O + O 2 . 
i cc. evolved oxygen = 0.003885 gram MnO 2 . 

If 0.3885 gram of pyrolusite is used in the determination, 
each cubic centimeter of evolved oxygen, reduced to standard 
conditions, is equivalent to one per cent of MnO 2 in the ore. 



THE LUNGE NITROMETER 403 

The weighed sample of very finely powdered manganese ore 
is placed in the outer compartment of the evolution flask. 5 cc. 
of a normal solution of sulphuric acid is run in upon the pyrolu- 
site. 25 cc. of a three per cent solution of hydrogen dioxide 
is next introduced into the inner tube of the flask. The flask 
is allowed to stand unstoppered for about five minutes or un- 
til the sulphuric acid has decomposed any carbonates that 
may be present in the pyrolusite. When the evolution of gas 
from the material in the outer compartment of the evolution 
flask has entirely ceased, the flask is connected to the gas burette 
in the usual manner and the hydrogen dioxide is brought into 
contact with the pyrolusite. The evolution flask is shaken for 
two minutes at the end of which time the reaction should be 
complete. If black particles of pyrolusite are still to be seen 
in the flask, the determination should be discarded and the ore 
should be more finely ground before a fresh sample is weighed 
out. The evolution flask should be shaken from time to time. 
If 0.3885 gram of pyrolusite has been used, the number of cubic 
centimeters of evolved oxygen, reduced to standard conditions, 
represents the per cent of maganese dioxide in the ore. 

The Determination of Carbon Dioxide in Sodium Carbon- 
ate. In this determination the nitrometer should be filled 
with mercury instead of with water as the confining liquid be- 
cause of the solubility of carbon dioxide in water. 

About 0.15 gram of the dry sodium carbonate or sodium bicar- 
bonate under examination is accurately weighed and is placed 
in the outer compartment of the evolution flask. 5 cc. of a 
normal solution of sulphuric acid is placed in the inner com- 
partment, the flask is connected with the burette and is then 
carefully tilted so that the sulphuric acid slowly drops upon the 
sodium carbonate. When all of the acid has been poured upon 
the salt the evolution flask should be thoroughly shaken. The 
carbon dioxide evolved is measured and is reduced to standard 
conditions. Since one cubic centimeter of carbon dioxide weighs 
0.001965 gram, the weight of the evolved carbon dioxide is equal 



404 GAS ANALYSIS 

to the corrected volume of the gas in cubic centimeters multi- 
plied by 0.001965. 

100 X grams CO^ evolved 



Per cent CO 2 



weight sodium carbonate in grams. 



Some carbon dioxide will of course remain dissolved in the 
liquid in the evolution flask. If very accurate results are de- 
sired it is preferable to employ a different method for this de- 
termination rather than to attempt to introduce a correction 
for the amount of this dissolved gas. 



GAS ANALYSIS 
International Atomic Weights, 1913 



405 





SYMBOL 


ATOMIC 
WEIGHT 




SYMBOL 


ATOMIC 
WEIGHT 


Aluminum 


Al 


27.1 


Neodymium 


Nd 


144-3 


Antimony 


. . Sb 


I 2O. 2 


Neon . . . 


. Ne 


2O. 2 


Argon 


. . A 


3Q.88 


Nickel . . . 


. Ni 


58.68 


Arsenic . 


. . As 


74.96 


Niton (radium 






Barium . 


. . Ba 


137-37 


emanation) 


Nt 


222.4 


Bismuth . 


. . Bi 


208.0 


Nitrogen 


. N 


I4.OI 


Boron . . 


. . B 


II .O 


Osmium . 


. Os 


190.9 


Bromine . 


. . Br 


79.92 


Oxygen . . . 


. 


16.00 


Cadmium 


Cd 


1 1 2 . 40 


Palladium . 


. Pd 


106.7 


Caesium . 


. . Cs 


I32.8I 


Phosphorus . 


. P 


3I-04 


Calcium . 


. . Ca 


40.07 


Platinum 


. Pt 


195-2 


Carbon . 


. . C 


12. OO 


Potassium 


. K 


39.10 


Cerium . 


. . Ce 


140.25 


Praseodymium . 


. Pr 


140.6 


Chlorine . 


. . Cl 


35-46 


Radium . 


. Ra 


226.4 


Chromium . 


. . Cr 


52.0 


Rhodium 


. Rh 


102.9 


Cobalt . . 


. Co 


58.97 


Rubidium . . 


. Rb 


85-45 


Columbium . 


. . Cb 


93-5 


Ruthenium . . 


. Ru 


101 .7 


Copper . 


. . Cu 


63-57 


Samarium 


. Sa 


150.4 


Dysprosium . 
Erbium . . 


. Dy 

. . Er 


162.5 
167.7 


Scandium 
Selenium 


. Sc 
. Se 


44.1 

79-2 


Europium 


. . Eu 


152.0 


Silicon 


. Si 


28.3 


Fluorine . 


. . F 


19.0 


Silver . . 


Ag 


107.88 


Gadolinium . 


. . Gd 


157-3 


Sodium . . . 


. Na 


23.00 


Gallium . . 


. . Ga 


69.9 


Strontium . 


Sr 


87-63 


Germanium . 


. . Ge 


72-5 


Sulphur . 


. S 


32.07 


Glucinum 


. . Gl 


9.1 


Tantalum 


. Ta 


181.5 


Gold . . . 


Au 


107 2 


Tellurium 


. Te 


127.5 


Helium . 


. . He 


7 1 ' *" 

3-99 


Terbium 


. Tb 


159-2 


Holmium 


. . Ho 


163.5 


Thallium . . 


Tl 


204.0 


Hydrogen 


. . H 


1.008 


Thorium 


. Th 


232.4 


Indium . 


. . In 


114.8 


Thulium 


. Tm 


168.5 


Iodine 


. . I 


126.92 


T ! n 


. Sn 


119.0 


Iridium . 


. . Ir 


i93-i 


Titanium 


. Ti 


48.1 


Iron . . . 


. . Fe 


55-84 


Tungsten . . 


. W 


184.0 


Krypton . . 


. . Kr 


82.92 


Uranium 


. U 


238-5 


Lanthanum . 


. . La 


139.0 


Vanadium 


. V 


51-0 


Lead . 


Pb 


207. 10 


Xenon 


. Xe 


130.2 


Lithium . 


. . Li 


6-94 


Ytterbium 






Lutecium 


. . Lu 


174.0 


(Neoytterbium) 


Yb 


172.0 


Magnesium . 


. . Mg 


24.32 


Yttrium . . . 


. Yt 


89.0 


M^anganese 


Mn 


^4. 0"^ 


Zinc . .. . - 


Zn 


65 .37 


Mercury . 


Hg 


OT* Vo 

200. 6 


Zirconium 


. Zr 


90.6 


Molybdenum 


. . Mo 


96.0 









4 o6 



GAS ANALYSIS 



Theoretical Densities of Gases 

and Weights of One Liter of the Same at o and 760 mm. pres- 
sure, at Sea Level and Latitude 45 



Substance 


Formula 


Molecular 
Weight 


Density 
Air i 


Weight of 
One Liter in 
Grams 


Acetylene 
Allylene 
Ammonia 
Arsine 


C 2 H 2 
C 3 H 4 
NH 3 
AsH 3 
Br 2 


26.02 
40.03 
17.03 
77.98 
I $Q . 84 


0.8988 
1.3819 

0.5895 
2.696 

c; C24Q 


1.1620 
1.7869 
0.7621 

3-485 
7 14.26 




C4Hio 


58.08 


2 0065 


2 ZQA 


Butylene 


C4H 8 


56.06 


I Q34.Q 


2 ^OIO 


Carbon dioxide .... 
Carbon monoxide . . ; 
Carbon oxysulphide . ; 
Carbonyl chloride . 
Chlorine .... 


CO 2 
CO 
COS 
COC1 2 
C1 2 


44.00 
28.00 
60.07 

98.92 

7O.O2 


I.520I 
0.9673 
2.0749 
3.4168 
2 4.AQ4. 


1.9652 
i . 2506 
2.6825 
4.4172 

3 1666 


Cyanogen ..... 


C 2 N 2 


Z2 O2 


I 700"? 


2 3261 


Ethane . . . ^ Y 


C 2 H 6 


2Q OS 


I 0381 


I 34.21 


Ethylene 


C 2 H 4 


28 01 


o 0684. 


I 2520 


Hydrogen . . 


H 2 


2 Ol6 


o 06965 


O OOOO4. 


Hydrogen bromide . . 
Hydrogen chloride . 
Hydrogen fluoride . . . 
Hydrogen iodide . . . 
Hydrogen selenide . . . 
Hydrogen sulphide . . . 
Hydrogen telluride . . , 
Methane . . . 


HBr 
HCI 
HF 
HI 
H 2 Se 
H 2 S 
H 2 Te 
CH 4 


80.93 
36.47 

20. 
127.93 
81.2 
34-09 
129.5 

16 03 


2.7973 

1 2595 
0.691 
4.4172 
2.8o6 

I-I773 
4.478 
O ^ ^30 


3.6163 
1.6283 
0.894 
5.7106 
3.627 
1.5230 
5.789 

o 7160 


Nitric oxide . 
Nitrogen .... . 
Nitrogen tetroxide . 
Nitrous oxide .... 
Oxygen . . . . 
Phosphine . . . . ~v 
Propane 
Propylene . . . . .' 
Silicon tetrafluoride , ' .! 
Sulphur dioxide 
Water vapor . .. . ., 


NO 

N 2 
NO 2 
N 2 O 
2 
PH 3 
C 3 H 8 
C 3 H 6 
SiF 4 
S0 2 
H 2 O 


30.01 
28.02 
46.01 
44.02 
32.00 
34.06 
44.06 
42.05 
104.3 
64.07 
18.016 


1.0378 
0.9701 
1.5906 
1.5229 
i 1055 
1-175 
1.5204 

1-4527 
3.607 
2.2131 
0.6218 


.3417 
.2542 

.0563 
.9688 
.4292 
.520 

.966 

.8780 

4.663 

2.8611 

o . 8040 


Atmospheric air . . 






i .0000 


1.2928 



GAS ANALYSIS 



407 



Reduction of a Gas Volume to o and 760 mm. 

If v is the volume of a gas at 1 and p mm. pressure, the vol- 
ume v of the gas at o and 760 mm. may be calculated with 
the aid of the formula 

= v P 

760 (i + 0.00367 /). 

To facilitate the reduction of gas volumes to standard condi- 
tions, the values of the expression (i + 0.003670 from 2 to 
+34 are given in the following table: 



1 




LOE I 


f 


i 


Log T 




,003 7* 


6 I +0.00367 / 




0.003 7 


i + 0.00367 / 




O, 


0, 




I, 


9, io 


2.0 


99266 


00320 


.I 


00404 


99825 


9 


99303 


00304 


.2 


00440 


99809 


.8 


99339 


00288 


3 


00477 


99793 


-7 


99376 


00272 


4 


00514 


99777 


.6 


99413 


00256 


.5 


00551 


9976i 


-5 


99449 


00240 


.6 


00587 


99746 


4 


99486 


00224 


7 


00624 


99730 


3 


99523 


00208 


.8 


00661 


99714 


.2 


99560 


00192 


9 


00697 


99698 


.1 


99596 


00176 


2.O 


00734 


99682 


.O 


99633 


00160 




I, 


9, io 




o, 


o, 


2.1 


00771 


99666 


O.Q 


99670 


00144 


2.2 


00807 


99651 


-0.8 


99706 


00128 


2-3 


00844 


99635 


0.7 


99743 


001 1 2 


2.4 


00881 


996i9 


0.6 


90780 


00096 


25 


00918 


99603 


o 5 


99816 


00080 


2.6 


"00954 


99588 


0.4 


99853 


00064 


2-7 


00991 


99572 


0.3 


99890 


00048 


2.8. 


01028 


99556 


0.2 


99927 


00032 


2.9 


01064 


99540 


O.I 


99963 


00016 


30 


OIIOI 


99524 


o.o 


100000 


ooooo 




I, 


9, io 




i, 


9, io 


3i 


01138 


99509 


+0.1 


00037 


99984 


32 


01174 


99493 


0.2 


00073 


99968 


33 


OI2II 


99477 


0-3 


OOIIO 


99952 


34 


01248 


99461 


0.4 


00147 


99936 


35 


01285 


99445 


o-5 


00184 


99920 


3-6 


OI32I 


9943 


0.6 


OO22O 


99905 


37 


01358 


99414 


0.7 


00257 


99889 


3-8 


01395 


99398 


0.8 


OO294 


99873 


39 


OI43I 


99383 


0.9 


00330 


99857 


4-0 


01468 


99367 


I.O 


00367 


99841 









Reduction of a Gas Volume to o and 760 mm. 

Value of (i + 0.00367 /) for / = 4.1 to 14.0 



t 


i + 0.00367 1 


LOE ' 


t 


i + 0.00367 1 


Ln _ i . 


g I + 0.00367 1 


g i + 0.00367 1 




i, 


9, 10 




i, 


9, 10 


4. i 


01505 


99351 


9- 1 


03340 


98573 


4.2 


01541 


99336 


9.2 


03376 


98558 


43 


01578 


99320 


93 


03413 


98542 


44 


01615 


99304 


94 


03450 


98527 


45 


01652 


99288 


95 


03487 


98511 


4.6 


01688 


99273 


9.6 


03523 


98496 


47 


01725 


99257 


97 


03560 


98481 


4-8 


01762 


99241 


9-8 


03597 


98465 


49 


01798 


99226 


99 


03633 


98450 


50 


01835 


99210 


10. 


03670 


98435 




li 


9, 10 




i, 


9, 10 


5-i 


01872 


99195 


10. 1 


03707 


98420 


52 


01908 


99179 


IO.2 


03743 


98404 


53 


01945 


99163 


10.3 


03780 


98389 


54 


01982 


99148 


10.4 


03817 


98373 


55 


02019 


99132 


10.5 


03854 


98358 


56 


02055 


99117 


10.6 


03890 


98343 


5-7 


02092 


99101 


10.7 


03927 


98327 


5-8 


02129 


99085 


10.8 


03964 


98312 


59 


02165 


99070 


10.9 


04000 


98297 


6.0 


O22O2 


99054 


II. 


04037 


98281 




I, 


9, 10 




i, 


9, 10 


6.1 


02239 


99038 


u. i 


04074 


98266 


6.2 


02275 


99023 


II. 2 


04110 


98251 


6-3 


02312 


99007 


ii. 3 


04147 


98235 


6.4 


02349 


98992 


11.4 


04184 


98220 


6-5 


02386 


98976 


11.5 


04221 


98204 


6.6 


02422 


98961 


11. 6 


04257 


98189 


6.7 


02459 


98945 


11.7 


04294 


98174 


6.8 


02496 


98929 


n. 8 


04331 


98i59 


6-9 


02532 


98914 


11.9 


04367 


98144 


7.0 


02569 


98899 


12. 


04404 


98128 




I, 


9, 10 




i, 


9, 10 


7i 


O26o6 


98883 


12. 1 


04441 


98113 


72 


02642 


98867 


12.2 


04477 


98098 


73 


02679 


98852 


12.3 


04514 


98083 


74 


02716 


98836 


12.4 


04551 


98067 


75 


02753 


98821 


12.5 


04588 


98052 


7-6 


02789 


98805 


12.6 


04624 


98037 


7-7 


02826 


98790 


12.7 


04661 


98022 


78 


02863 


98774 


12.8 


04698 


98006 


79 


02899 


98759 


12.9 


04734 


97991 


8.0 


02936 


98743 


13 o 


04771 


97976 




I, 


9, 10 




i, 


9, 10 


8.1 


02973 


98728 


I3-I 


04808 


97961 


8.2 


03009 


98712 


13-2 


04844 


97945 


8.3 


03046 


98697 


13-3 


04881 


97930 


8.4 


03083 


98681 


13-4 


04918 


97915 


8-5 


03120 


98666 


13 5 


04955 


97900 


8.6 


03156 


98651 


13 6 


04991 


97885 


8-7 


03193 


98635 


13-7 


05028 


97869 


8.8 


03230 


98619 


13-8 


05065 


97854 


8-9 


03266 


98604 


13 9 


05101 


97839 


90 


03303 


98589 


14.0 


05138 


97824 



408 



Reduction of a Gas Volume to o and 760 mm. 

Value of (i + 0.00367 /) for / =14.1 to 24.0 



/ 


i + 0.00367 / 


Log * 


/ 


i + 0.00367 / 


Loe ' 


i + 0.00367 / 


S I + 0.00367 1 




i, 


9, 10 




i, 


9, 10 


14. i 


05175 


97809 


19. i 


07010 


97058 


14.2 


05211 


97794 


19.2 


07046 


97043 


14 3 


05248 


97779 


19 3 


07083 


97028 


14.4 


05285 


97763 


19.4 


07120 


97013 


14 5 


05322 


97748 


19 5 


07157 


96998 


14-6 


05358 


97733 


19.6 


07193 


96983 


14.7 


05395 


97718 


19.7 


07230 


96968 


14.8 


05432 


97703 


19.8 


07267 


96954 


14.9 


05468 


97688 


19.9 


07303 


96939 


15 o 


05505 


97673 


20. o 


07340 


96924 




i, 


9, 10 




li 


9, 10 


15 i 


05542 


97657 


20. i 


07377 


96909 


15 2 


05578 


97642 


20.2 


07413 


96894 


15 3 


05615 


97627 


20.3 


07450 


96879 


15-4 


05652 


97612 


20.4 


07487 


96864 


15 5 


05689 


97597 


20.5 


07524 


96850 


15-6 


05725 


97582 


20.6 


07560 


96835 


15 7 


05762 


97567 


20.7 


07597 


96820 


15-8 


05799 


97552 


20.8 


07634 


96805 


15 9 


05835 


97537 


20.9 


07670 


96791 


16.0 


05872 


97522 


21.0 


07707 


96776 




tj 


9, 10 




i, 


9, 10 


16.1 


05909 


97507 


21. 1 


07744 


96761 


16.2 


05945 


97492 


21.2 


07780 


96746 


16.3 


05982 


97477 


21.3 


07817 


96731 


16.4 


06019 


97462 


21.4 


07854 


96716 


16-5 


06056 


97447 


21-5 


07891 


96702 


16.6 


06092 


97432 


21.6 


07927 


96687 


16.7 


06129 


97417 


21.7 


07964 


96672 


16.8 


06166 


97402 


21.8 


08001 


96657 


16.9 


06202 


97387 


21.9 


08037 


96643 


17.0 


06239 


97372 


22.0 


08074 


96628 




i, 


9, 10 




i, 


9, 10 


17.1 


06276 


97357 


22.1 


08111 


96613 


17.2 


06312 


97342 


22.2 


08147 


96598 


17 3 


06349 


97327 


22.3 


* 08184 


96584 


17.4 


06386 


97312 


22.4 


08221 


96569 


17 5 


06423 


97297 


22.5 


08258 


96554 


17-6 


06459 


97282 


22.6 


08294 


96539 


17.7 


06496 


97267 


22.7 


08331 


96525 


178 


06533 


97252 


22.8 


08368 


96510 


17.9 


06569 


97237 


22.9 


08404 


96495 


18.0 


06606 


'97222 


23.0 


08441 


96481 




i, 


9, 10 




i, 


9, 10 


18.1 


06643 


97207 


23-1 


08478 


96466 


18.2 


06679 


97192 


23.2 


08514 


96451 


18-3 


06716 


97177 


23 3 


08551 


96437 


18.4 


06753 


97162 


23 4 


08588 


96422 


18.5 


06790 


97147 


23 5 


08625 


96407 


18.6 


06826 


97132 


23.6 


08661 


96393 


18.7 


06863 


97117 


23 7 


08698 


96378 


18.8 


06900 


97102 


23.8 


08735 


96363 


18.9 


06936 


97088 


23 9 


08771 


96349 


19 o 


06973 


9/073 


24.0 


08808 


96334 



409 



Reduction of a Gas Volume to o and 760 mm. 

Value of (i + 0.00367 i) for t =24.1 to 34.0. 



t 


i + 0.00367 1 


Loz x 


t 


i + 0.00367 1 


Loc * 


6 i + 0.00367 t 


* i + 0.00367 t 




i, 


9, 10 




i, 


9, io 


24. I 


08845 


96319 


29. i 


10680 


95593 


24.2 


08881 


96305 


29.2 


10716 


95579 


24 3 


08918 


96290 


29 3 


10753 


95565 


24.4 


08955 


96275 


29.4 


10790 


95550 


24 5 


08992 


96261 


29 5 


10827 


95535 


24.6 


09028 


96246 


29.6 


10863 


9552i 


24.7 


09065 


96231 


29.7 


10900 


95507 


24.8 


09102 


96217 


29.8 


10937 


95492 


24.9 


09138 


96202 


29.9 


10973 


95478 


25.0 


09175 


96188 


30.0 


IIOIO 


95464 




i, 


9, 10 




Ii 


9, io 


25.1 


09212 


96173 


30.1 


11047 


95449 


25 2 


09248 


96i59 


30.2 


11083 


95435 


25 3 


09285 


96144 


30.3 


in 20 


95421 


25 4 


09322 


96129 


30-4 


IH57 


95406 


25 5 


09359 


96115 


30-5 


11194 


95392 


25.6 


09395 


96100 


30.6 


11230 


95378 


25 7 


09432 


96086 


30-7 


11267 


95363 


25.8 


09469 


96071 


30.8 


11304 


95349 


25 9 


09505 


96057 


30-9 


11340 


95335 


26.0 


09542 


96042 


31 o 


H377 


95320 




i, 


9, 10 




i, 


9, io 


26.1 


09579 


96027 


31.1 


11414 


95306 


26.2 


09615 


96013 


31 2 


11450 


95292 


263 


09652 


95998 


3i 3 


11487 


95278 


26.4 


09689 


95984 


3i 4 


11524 


95263 


26.5 


09726 


95969 


3i 5 


11561 


95249 


26.6 


09762 


95955 


31-6 


H597 


95235 


26.7 


09799 


95940 


3i 7 


11634 


95220 


26.8 


09836 


95925 


31-8 


11671 


95206 


26.9 


09872 


95901 


3i-9 


11707 


95192 


27.0 


09909 


95897 


32.0 


11744 


95178 




i, 


9, 10 




i, 


9, io 


27.1 


09946 


95882 


32.1 


11781 


95163 


27.2 


09982 


95868 


32.2 


11817 


95H9 


27 3 


10019 


95853 


32 3 


11854 


95135 


27.4 


10056 


95839 


32-4 


11891 


95120 


27 5 


10093 


95824 


32-5 


11928 


95106 


27.6 


10129 


95810 


32.6 


11964 


95092 


27.7 


10166 


95795 


32-7 


I2OOI 


95078 


27-8 


10203 


9578i 


32-8 


12038 


95064 


27.9 


10239 


95767 


32-9 


12074 


95049 


28.0 


10276 


95752 


33 o 


I2III 


95035 




I, 


9, 10 




If 


9, io 


28.1 


10313 


95737 


33 i 


12148 


95021 


28.2 


10349 


95723 


33 2 


12184 


95007 


28.3 


10386 


95709 


33 3 


I222I 


94993 


28.4 


10423 


95694 


33 4 


12258 


94978 


28.5 


10460 


95679 


33 5 


12295 


94964 


28 6 


10496 


95665 


33 6 


I233I 


94950 


28 7 


10533 


95651 


33 7 


12368 


94936 


28.8 


10570 


95636 


33-8 


12405 


94922 


28.9 


10606 


95622 


33 9 


12441 


94907 


29.0 


10643 


956o8 


34 o 


12478 


94893 



410 



Tension of Aqueous Vapor 

Expressed in millimeters of mercury at o, density of mercury 

= 13.59593 at latitude 45 and at the sea-level 
Calculated from Regnault's measurements by Broch (Trav. et 
Mem. du Bur. intern, des Poids et Mes. I A. 33, 1881) 



1 


Tension 


t 


Tension 


t 


Tension 


t 


Tension 




mm. 




mm. 




mm. 




mm. 


2.0 


3 9499 


2. 6 


5 5008 


7. i 


7.5I7I 


11. 6 


10.1614 


1.9 


3.9790 


2-7 


5-5398 


7-2 


7.5685 


11.7 


10.2285 


1.8 


4.0082 


2.8 


5-5790 


73 


7.6202 


ii. 8 


10.2960 


-7 


4.0376 


2.9 


5-6185 


74 


7.6722 


11.9 


10.3639 


.6 


4.0672 


30 


5.6582 


75 


7.7246 


12. 


10.4322 


-5 


4.0970 






7.6 


7-7772 








4.1271 


31 


5-6981 


7-7 


7.8302 


12. 1 


IO . 5009 


3 


4-1574 


32 


5.7383 


7.8 


7-8834 


12.2 


10.5700 


.2 


4-1878 


33 


5.7788 


79 


7.9370 


12.3 


10.6394 


.1 


4.2185 


34 


5-8I95 


8.0 


7.9909 


12.4 


10.7093 






35 


5-8605 






12-5 


10.7796 


I.O 


4 2493 


36 


5-90I7 


8.1 


8.0452 


12.6 


10.8503 


O . Q 


4 . 2803 


3-7 


5-9432 


8.2 


8.0998 


12.7 


10.9214 


o 

o . o 


4.3116 


38 


5-9850 


8-3 


8.1547 


12.8 


10.9928 


0.7 


4-3430 


39 


6.0270 


8-4 


8.2099 


12.9 


II .0647 


0.6 


4-3747 


4.0 


6.0693 


8-5 


8.2655 


13 o 


11.1370 


5 


4.4065 






8.6 


8.3214 






0.4 


4.4385 


4-1 


6.III8 


8.7 


8-3777 


I3-I 


11.2097 


03 


4.4708 


4.2 


6.1546 


8.8 


8.4342 


13 2 


11.2829 


0.2 


4-5032 


43 


6-1977 


8.9 


8.4911 


13 3 


H.3564 


O.I 


4-5359 


44 


6.2410 


9.0 


8.5484 


13 4 


11.4304 






45 


6 . 2846 






13 5 


11.5048 


o.o 


4-5687 


4.6 


6.3285 






13 6 


11-5797 


+ 0.1 


4.6017 


47 


6.3727 


9-1 


8. 6061 


13 7 


11.6550 


0.2 


4-6350 


4.8 


6.4171 


9.2 


8.6641 


13-8 


11.7307 


0-3 


4.6685 


49 


6.4618 


93 


8.7224 


13 9 


11.8069 


0.4 


4.7022 


5.0 


6.5067 


94 


8.7810 


14.0 


11.8835 


05 


4. 7361 








8.8400 






0.6 


4-7703 






9.6 


8.8993 






0.7 


4 . 8047 


5.1 


6.5519 


97 


8.9589 


14.1 


11.9605 


0.8 


4.8393 


52 


6-5974 


9-8 




14.2 


12.0380 


0.9 


4.8741 


53 


6.6432 


99 


9.0792 


14 3 


12.1159 


I.O 


4.9091 


5-4 


6.6893 


IO.O 


9.1398 


14.4 


12.1943 






55 


6-7357 






14-5 


12.2731 


.1 


4-9443 


56 


6.7824 


IO.I 


9.2009 


14.6 


12.3523 


.2 


4.9798 


57 


6.8293 


IO.2 


9.2623 


14-7 


12.4320 


3 


5-0155 


5-8 


6.8765 


10.3 


9.3241 


14.8 


12.5122 


4 


5-0515 


59 


6.9240 


10.4 


9-3863 


14 9 


12.5928 


5 


5-0877 


6.0 


6.9718 


IO.5 


9.4488 


15-0 


12.6739 


.6 


5.1240 






10.6 


9.5117 






7 


5.1606 


6.1 


7.0198 


10.7 


9-5750 


15-1 


12-7554 


.8 


5.1975 


6.2 


7.0682 


10.8 


9.6387 


15 2 


12.8374 


9 


5.2346 


6-3 


7.1168 


10.9 


9.7027 


15 3 


12.9198 


.0 


5-27I9 


6.4 


7-1658 


II. 


9.7671 


15 4 


13.0027 






6-5 


7.2150 






15 5 


13.0861 


2.1 


5.3094 


6.6 


7 . 2646 


ii. i 


9.8318 


15 6 


13.1700 


2.2 


5-3472 


6.7 


7.3145 


II. 2 


9.8969 


15 7 


I3-2543 


23 


5-3852 


6.8 


7-3647 


11.3 


9.9624 


15-8 


I3.3392 


2-4 


5.4235 


69 


7-4152 


II .4 


10.0283 


15 9 


I3-4245 


2-5 


5.4620 


7.0 


7.4660 


ii 5 


10.0946 


16.0 


I3-5I03 



Tension of Aqueous Vapor. Continued 



I Tension 


t 


Tension 


/ Tension 


/ 


Tension 




mm. 




mm. 




mm. 




mm. 


i6.i 


I3-5965 


20. 6 


18.0176 


25- 1 


23-6579 


29. 6 


30.7928 


16.2 


13.6832 


20.7 


18.1288 


25-2 


23.7991 


29.7 


30.9707 


16.3 


I3-7705 


20.8 


18.2406 


25 3 


23.9411 


29.8 


31.1494 


16.4 


13.8582 


20.9 


18.3529 


25 4 


24.0838 


29.9 


31.3291 


16.5 


13.9464 


21.0 


18.4659 


25 5 


24.2272 


30.0 


31.5096 


16.6 


I4-035I 






25-6 


24.3714 






167 


14.1243 


21. 1 


18.5795 


25 7 


24.5164 


30.1 


31.6910 


16.8 


14.2141 


21.2 


18.6937 


25-8 


24.6620 


30.2 


3I-8734 


16.9 


I4-3043 


21.3 


18.8085 


25 9 


24 . 8084 


30.3 


32-0567 


17.0 


I4-3950 


21.4 


18.9240 


26.0 


24-9556 


30.4 


32.2410 






21-5 


19.0400 






30-5 


32.4262 


17.1 


14.4862 


21.6 


19.1567 


26.1 


25.1035 


30.6 


32.6124 


17.2 


14-5779 


21-7 


19.2740 


26.2 


25-2523 


30.7 


32-7995 


17 3 


14.6702 


21.8 


19.3920 


26.3 


25.4018 


30.8 


32.9875 


17 4 


14.7630 


21.9 


I9-SI05 


26.4 


25.5521 


30.9 


33-I765 


17 5 


14.8563 


22.0 


19.6297 


26.5 


25.7032 


31.0 


33-3664 


17.6 


14.9501 






26.6 


25-855I 






17.7 


15.0444 


22.1 


19.7496 


26.7 


26.0077 


31-1 


33-5573 


17-8 


I5-I392 


22.2 


19.8701 


26.8 


26.l6l2 


31 2 


33-7491 


17.9 


I5-2345 


22.3 


19.9912 


26.9 


26^155 


31-3 


33.94I9 


18.0 


15.3304 


22.4 


2O. 1130 


27.0 


26.4705 


3i 4 


34-I356 






22.5 


20.2355 






3i 5 


34-3303 


18.1 


15.4268 


22.6 


20.3586 


27.1 


26.6263 


31-6 


34-5259 


18.2 


I5-5237 


22.7 


20.4824 


27.2 


26.7830 


31-7 


34-7225 


18.3 


15.6212 


22.8 


20.6068 


27 3 


26 . 9405 


31-8 


34.9201 


18.4 


15.7192 


22.9 


20.7319 


27.4 


27.0987 


3i 9 


35.1186 


18.5 


15.8178 


23.0 


20.8576 


27 5 


27.2578 


32.0 


35-3i8i 


18.6 


15.9169 






27.6 


27.4177 






18.7 


16.0166 


23.1 


20.9840 


27.7 


27-5784 


32.1 


35-5i86 


18.8 


16.1168 


23.2 


2I.IIIO 


27.8 


27-7399 


32.2 


35.7201 


18.9 


16.2176 


23 3 


21.2388 


27.9 


27.9023 


32-3 


35.9226 


19.0 


16.3189 


23 4 


21.3672 


28.0 


28.0654 


32.4 


36.1261 






23 5 


21.4964 






32-5 


36-3307 


19.1 


16.4208 


23.6 


21.6262 


28.1 


28.2294 


32 6 


36-5363 


19.2 


16.5233 


23 7 


21.7567 


28.2 


28.3942 


32-7 


36.7429 


iQ 3 


16.6263 


23.8 


21.8879 


28.3 


28.5599 


32.8 


36-9505 


19.4 


16.7299 


23 9 


22.0198 


28.4 


28.7265 


32 9 


37-1592 


19 5 


16.8341 


24.0 


22.1524 


28.5 


28.8939 


33 -o 


37-3689 


19-6 


16.9388 






28.6 


29.0622 






19.7 


17.0441 


24.1 


22.2857 


28.7 


29.2313 


33 i 


37-5796 


19.8 


17.1499 


24.2 


22.4196 


28.8 


29.4013 


33 2 


37-79H 


19.9 


17.2563 


24 3 


22-5543 


29.9 


29.5722 


33 3 


38.0042 


20.0 


17-3632 


24.4 


22.6898 


29.0 


29.7439 


33 4 


38.2180 






24 5 


22.8259 






33 5 


38.4329 


2O. I 


17.4707 


24.6 


22.9628 


29.1 


29.9165 


33 6 


38.6488 


20.2 


17-5789 


24-7 


23 . 1003 


29.2 


30.0900 


33-7 


38-8657 


20.3 


17.6877 


24.8 


23.2386 


29 3 


30.2644 


33 8 


39-o837 


20.4 


17.7971 


24.9 


23-3777 


29.4 


30.4396 


33 9 


39.3027 


20.5 


17.9071 


25.0 


23-5I74 


29 5 


30.6157 


34 -o 


39.5228 



412 



INDEX OF AUTHORS' NAMES 



Albrecht, determination of naph- 
thalene, 260 

Allen, applications of Lunge ni- 
trometer, 397 

Anderson, combustion of gases, 
127; determination of carbon 
dioxide in air, 387 

Andrews, detection of ozone, 172; 
determination of hydrogen cya- 
nide, 269 

Anneler, determination of ozone, 
179, 181 

Arago, refraction of gases, 305 

Arndt, determination of nitrous 
oxide, 214; methane in acety- 
lene, 269 

Arnold, detection of ozone, 172, 

173, 174 
August, psychrometer, 375 

B 

Bamberger, evaluation of calcium 

carbide, 363 

Barreswill, detection of ozone, 172 
Bartlett, determination of carbon 

monoxide with iodine pentox- 

ide, 237 
Baskerville, determination of nitrous 

oxide, 215 

Beagle, heating value of coal, 335 
Benedict, preparation of alkaline 

pyrogallol, 160; composition of 

the atmosphere, 371; relation of 

carbon dioxide to oxygen in 

air, 377 



Bernthsen, hyposulphurous acid. 168 
Biot, refraction of gases, 304 
le Blanc, absorption of nitric ox- 
ide, 218 
Bleier, apparatus for carbon dioxide 

in air, 387 

Bodlander, gas baroscope, 40 
Boettger, detection of ozone, 172 
Broch, tension of aqueous vapor, 411 
Brunck, absorption of hydrogen, 
184; fractional combustion of 
hydrogen, 194 

Briinnich, detection of cyanogen, 263 
Bunsen, collection of gases from 
springs, 15; collection of gases 
dissolved in water, 19; collection 
of gases from reactions in sealed 
tubes, 21 ; determination of specific 
gravity of a gas, 44; proportion 
of gases in analysis by explosion, 
143; oxy hydrogen gas generator, 
145; hydrogen apparatus, 159; 
solubility of hydrogen in alcohol, 
181; solubility of nitrogen in 
water, 206; solubility of methane 
in water, 240; solubility of ethylene 
in water, 248; solubility of hydro- 
gen sulphide, 270; determination 
of chlorine, 285; photometer, 308 
Bunte, gas burette, 74; combustion 
of hydrogen with palladium, 192 



Carius, solubility of oxygen in alco- 
hol, 158; solubility of nitrogen in 
alcohol, 207; solubility of nitrous 



413 



414 



INDEX OF AUTHORS' NAMES 



oxide, 213; solubility of nitric 
oxide in alcohol, 217; solubility 
of ethylene in alcohol, 249 

Caro, sulphur compounds in crude 
acetylene, 368 

de Castro, fractional combustion of 
hydrogen, 200 

Cedercreutz, determination of phos- 
phorus in acetylene, 358 

Centnerszwer, absorption of oxygen 
by phosphorus in solution, 166 

Chapman, brass suction pump, 8 

Christie, determination of chlo- 
rine, 286 

Clausman, absorption of carbon 
monoxide, 234 

Collie, automatic device for circula- 
tion of gas, 209 

Colman, determination of naphtha- 
lene, 260 

Coquillion, combustion pipette, 147; 
combustion with metallic palla- 
dium, 192 

Crum, reduction of oxides of nitro- 
gen by mercury, 393 



Davies, determination of benzene, 
258 

Davis, determination of nitric oxide, 
222 

Denham, combustion of methane, 
194 

Dennis, gas absorption pipette, 81; 
modified -form of Orsat apparatus, 
86; combustion of gases in com- 
bustion pipette, 153; absorption 
of benzene by alcohol, 253; ab- 
sorption of benzene with nickel 
solution, 255; determination of 
phosphorus in acetylene, 360; mod- 
ified Hempel nitrometer, 393 



Dennstedt, absorption of oxygen by 
chromous chloride, 169 

Dittmar, collection of gases dis- 
solved in water, 19; solubility of 
hydrogen chloride, 289 

Divers, determination of nitric ox- 
ide, 219 

Doepner, detection of carbon mon- 
oxide in blood, 231 

Doyere, gas pipette, 53, 105; ap- 
paratus for gas analysis, 99 

Drehschmidt, platinum combustion 
pipette, 154; absorption of carbon 
monoxide by cuprous chloride, 
233; determination of total sul- 
phur, 319 

Dulong, refraction of gases, 304 

von Dumreicher, determination of 
nitrous oxide, 214 

Dupasquier, determination of hydro- 
gen sulphide, 272 

E 

Eckardt, properties of Griess's re- 
agent, 218; reaction of arsine and 
silver nitrate, 292; detection of 
arsine, 293 
Eitner, determination of phosphorus 

in acetylene, 358 
Engler, detection of ozone, 172 
Erlwein, detection of ozone, 172 
Ettling, gas pipette, 53, 100, 105 



Feder, determination of sulphur in 

coal gas, 323 
Fisher, Franz, detection of ozone, 

173; absorption of nitrogen, 209, 

211, 212 
Fraenkel, amount of phosphine in 

crude acetylene, 357; determina- 



INDEX OF AUTHORS' NAMES 



tion of phosphorus, in acetylene, 
358; silicon hydride in crude 
acetylene, 368 

Franzen, furnace sampling tube, i; 
glass sampling tube, 7; absorption 
of oxygen by sodium hyposulphite, 
168, 169 

Fresenius, combustion of hydro- 
carbons, 198; determination of hy- 
drogen sulphide, 272; determina- 
tion of chlorine and hydrochloric 
acid, 288 

Friedrichs, spiral gas washing bottle, 
81, 123 

Frischer, preparation of cuprous 
chloride, 233 

Fritzsche, separation of ethylene 
from butylene, 250; determination 
of naphthalene, 260 



Gair, determination of naphthalene, 
260 

Ganassini, detection of hydrogen 
sulphide, 271 

Gautier, absorption of carbon mon- 
oxide, 234; determination of carbon 
monoxide with iodine pentoxide, 

235 

Genzken, autolysator, 303 

Gill, determination of carbon mon- 
oxide with iodine pentoxide, 237 



Haber, manipulation of Bunte bu- 
rette, 78; absorption of ethylene 
by bromine, 249; separation of 
ethylene from benzene, 250; sepa- 
ration of benzene from ethylene, 
255; determination of benzene, 
258; gas refractometer, 304 



Hahn, position of burette in Orsat 

apparatus, 84 

Hahnei, absorption of nitrogen, 211 
Haldane, colorimetric determination 

of carbon monoxide, 237 
Harbeck, determination of benzene, 

254 

Harding, determination of benzene, 
258; burner for sulphur determina- 
tion, 323 

de la Harpe, detection of carbon 
monoxide, 231 

Hartmann, absorption of hydro- 
gen, 182 

Hassler, absorption of oxygen by 
chromous chloride, 169 

Hempel, air sampling tubes, 3; 
simple gas burette, 51; absorption 
apparatus, 53; absorption of oxy- 
gen and carbon monoxide, 78; 
burette with correction tube, 90; 
mercury absorption apparatus, 96; 
apparatus for exact gas analysis, 
99; explosion pipette, 142; oxy- 
hydrogen gas generator, 145; 
hydrogen pipette, 145; explosion 
pipette for exact analysis, 146; 
hydrogen pipette for exact analy- 
sis, 147; absorption of oxygen by 
pyrogallol, 160; absorption of hy- 
drogen by colloidal palladium, 185; 
absorption of hydrogen by palla- 
dium black, 1 88; palladium sponge, 
193; determination of hydrogen 
with palladium asbestos, 195; 
fractional combustion of hydrogen 
with palladium black, 196; ab- 
sorption of nitrogen by various 
substances, 207; determination 
of nitrous oxide, 214; combustion 
of methane in combustion pipette, 
246; absorption of benzene by 



4 i6 



INDEX OF AUTHORS' NAMES 



alcohol, 253; absorbents for carbon 
oxysulphide, 278; determination of 
carbon oxysulphide, 279; determi- 
nation of fluorine, 280; nitro- 
meter, 393 

Henry, fractional combustion of hy- 
drogen, 192 

Hesse, carbon dioxide in air, 377 
Hoffman, furnace sampling tube, i; 

glass sampling tube, 7 
Hofmann, ammonia benzene nickel 

cyanide, 255 

Honigmann, gas burette, 72 
Hopkins, combustion of gases in 

combustion pipette, 153 
Hopp, sulphur in coal gas, 324 
Hoppe-Seyler, collection of gases 

dissolved in water, 19 
Houzeau, detection of ozone, 171 
Hulett, distillation of mercury, 117 
Huntly, gas sampling tube, 5 



Ilosvay, Griess's reagent, 218 



Jacobsen, removal of carbon dioxide 
from water, 21 

Jager, fractional combustion of hy- 
drogen, 198 

Johoda, autolysator, 303 

von Jolly, determination of oxygen, 

159 

Jorissen, determination of naphtha- 
lene, 260 

Junkers, gas calorimeter, 347; auto- 
matic gas calorimeter, 354 



Kampschulte, detection of ozone, 1 73 
Keiser, detection of ozone, 171 



Kellner, heating value of liquid fuel, 
347 

Keppeler, carbon monoxide in acety- 
lene, 355; determination of phos- 
phorus in acetylene, 358; deter- 
mination of carbon monoxide 
in acetylene, 369. 

Keyes, collection of gas from mer- 
cury pump, 13; lubricant for stop- 
cocks, 116 

Kinnicutt, determination of carbon 
monoxide with iodine pentoxide, 

235 

Klason, carbon oxysulphide, 278 

von Knorre, fractional combustion 
of hydrogen, 199; determination 
of nitrous oxide, 214; methane 
in acetylene, 369 

Kohn-Abrest, removal of oxygen 
from air, 230 

Kopfer, platinum asbestos, 193 

Korting, steam aspirator, 8 

Kostin, absorption of oxygen by 
ferrous salts, 168; removal of oxy- 
gen from air, 229 

Kreidl, determination of sulphur 
dioxide, 276 

Kreusler, determination of oxygen, 

iS9 

Kunkel, detection of carbon mon- 
oxide in blood, 231 

Kunz-Krause, detection of cyanogen, 
262, 263 

Kiispert, ammonia benzene nickel 
cyanide, 255 



Lassaigne, reaction of arsine and 

silver nitrate, 292 

Lemoult, detection of phosphine, 291 
Levy, detection of carbon monoxide, 

231 



INDEX OF AUTHORS' NAMES 



417 



Lewes, determination of ammonia in 
crude acetylene, 357 

Liebenthal, photometry, 305 

Limpricht, reduction of dinitroben- 
zene, 255 

Lindemann, absorption of oxygen 
by solid phosphorus, 163 

Lloyd, hygrodeik, 375 

Lockemann, properties of Griess's 
reagent, 218; reaction of arsine 
and silver nitrate, 292; detection 
of arsine, 293 

Lundstrom, carbon monoxide in acet- 
ylene, 369 

Lunge, gas volumeter, 37; detection 
of nitrous oxide, 213; preparation 
of Griess's reagent, 218; determina- 
tion of nitric oxide, 220, 222; 
determination of benzene, 254; 
determination of sulphur dioxide, 
275; determination of carbon 
oxysulphide, 279; ten-bulb tube, 
359; nitrometer, 393, 397 



M 

McCarthy, determination of ben- 
zene, 256 

McMaster, detection of ozone, 
171 

McWhorter, determination of carbon 
monoxide with iodine pentoxide, 

235 

Manchot, detection of ozone, 173 
Marx, detection of ozone, 173 
Mentzel, detection of ozone, 172, 

173, 174 
Misteli, determination of hydrogen 

by explosion, 144, 186 
Moissan, preparation of chromous 

chloride, 169; hydrogen sulphide 

in crude acetylene, 367 



Moody, determination of ethylene, 

249 
Morgan, determination of carbon 

monoxide with iodine pentoxide, 

235 
Moser, determination of nitric oxide, 

219, 220, 222 
Miiller, absorption of benzene, 254; 

determination of naphthalene, 260 



N 

Naccari, solubility of carbon dioxide, 
225 

Nauss, determination of cyanogen, 
263 

Nesmjelow, fractional combustion 
of hydrogen, 195; preparation of 
palladium asbestos, 195; fractional 
combustion of carbon monoxide, 

239 

Nicloux, determination of carbon 
monoxide with iodine pentoxide, 

235 

Nowicki, determination of carbon 
monoxide with iodine pentoxide, 
235 



O'Brien, determination of phos- 
phorus in acetylene, 358 

Oechelhauser, absorption of ethy- 
lene by bromine, 249; separation 
of ethylene from benzene, 250; 
separation of benzene from ethy- 
lene, 255 

Oettel, determination of fluorine, 280 

Offerhaus, suction device, 8; determi- 
nation of chlorine, 285 

Ogier, removal of oxygen from air, 
230 



4 i8 



INDEX OF AUTHORS' NAMES 



O'Neill, determination of benzene, 

253, 255 
Orsat, apparatus for gas analysis, 78 



Paal, absorption of hydrogen, 182 

Pagliani, solubility of carbon dioxide, 
225 

Palmqvist, determination of carbon 
dioxide in air, 382 

Pannertz, determination of specific 
gravity of gases, 47 

Paul, vitiation of air, 376 

Pecoul, detection of carbon mon- 
oxide, 231 

Petschek, absorption of hydrogen, 
1 86 

Pettenkofer, carbon dioxide in air, 

377 

Pettersson, removal of carbon diox- 
ide from water, 21; compensating 
tube, 90; solubility of oxygen in 
water, 158; solubility of nitrogen 
in water, 207; determination of 
carbon dioxide in air, 382 

Pfeifer, manipulation of Orsat ap- 
paratus, 84 

Pfeiffer, determination of benzene, 
254, 258 

von der Pfordten, preparation of 
chromous chloride, 169 

Phillips, detection of hydrogen, 181 

Preusse, collection of gases dis- 
solved in liquids, 16 



Raken, determination of carbon, 
monoxide with iodine pentoxide, 

237 
Ramsey, collection of gases from 



springs, 15; collection of gases 
from minerals, 22 

Raschig, determination of sulphur 
dioxide in presence of nitrous acid, 
276 

Reckleben, properties of Griess's re- 
agent, 218; reaction of arsine and 
silver nitrate, 292; detection of 
arsine, 293 

Regnault, tension of aqueous vapor, 
411. 

Reich, determination of sulphur 
dioxide, 274 

Reichardt, collection of gases dis- 
solved in liquids, 16 

Reinhardt, confining liquid in gasom- 
eters, 26 

Reverdine, detection of carbon mon- 
oxide, 231 

Rhodes, efficiency of absorption 
apparatus, 81; formation of oxides 
of nitrogen in combustion pipette, 
153; detection and determination 
of cyanogen, 265 

Richardt, fractional combustion of 
hydrogen, 193, 194 

Ringe, absorption of nitrogen, 212 

Rolland, apparatus for determina- 
tion of carbon dioxide, 78 

Rosa, photometric units, 307; heat- 
ing value of gaseous fuels, 352 

Roscoe, solubility of hydrogen chlo- 
ride, 289 

Rossel, methane in acetylene, 369 

Rutten, determination of naphtha- 
lene, 260 



Samtleben, cyanogen in gas, 265 
Sandmeyer, preparation of cuprous 

chloride, 232 
Sandriset, methane in acetylene, 369 



INDEX OF AUTHORS' NAMES 



419 



Sanford, determination of carbon 
monoxide with iodine pentoxide, 

235 

Saussure, carbon dioxide in air, 377 

Schaer, detection of cyanogen, 262 

Scheffier, determination of fluorine, 
280 

Scheiber, determination of acety- 
lene, 252 

Scheurer-Kestner, combustion of hy- 
drocarbons, 198 

Schilling, determination of specific 
gravity of gases, 46 

Schlosing, apparatus for determina- 
tion of carbon dioxide, 78 

Schonbein, detection of ozone, 171, 
172; determination of nitric oxide, 
221 

Schonbein-Pagenstecher, detection of 
cyanogen, 262 

Schoene, detection of ozone, 172 

Schoenn, detection of ozone, 172 

Schonfeld, solubility of chlorine, 285 

Schumacher, determination of sul- 
phur in coal gas, 323 

Schutzenberger, hyposulphurous 
acid, 1 68 

Simmance-Abady, carbon dioxide 
recorder, 300 

Sims, solubility of sulphur dioxide, 

273 

de Smet, combustion of gases, 127 

Smith, determination of naphtha- 
lene, 260 

Smits, determination of carbon mon- 
oxide with iodine pentoxide, 237 

Sonden, solubility of oxygen, 158; 
solubility of nitrogen, 207 

Stavorinus, determination of ben- 
zene, 258, 260 

Stevenson, determination of nitrous 
oxide, 215 



Stockmann, combustion of hydro- 
carbons, 198 

Stokes, absorption of ethylene by 
bromine, 249 

Strache, autolysator, 303 

Struve, detection of ozone, 172 



Tait, detection of ozone, 172 

Taylor, determination of benzene, 
258 

Teclu, explosive limits of gas mix- 
tures, 143 

Terreil, determination of nitric oxide, 

220 

Tiemann, collection of gases dis- 
solved in liquids, 16 

Timofejew, solubility of hydrogen, 
181 

Topler, mercury pump, 9 

Torwogt, determination of carbon 
monoxide with iodine pentoxide, 

237 
Travers, Topler pump, 9; collection 

of gases from mineral waters, 15; 

collection of gases from minerals, 

22; removal of nitrogen from the 

air, 209 
Treadwell, determination of ozone, 

179, 181; absorption of ethylene 

by bromine, 249; determination of 

chlorine, 285, 286 
Tucker, determination of ethylene, 

249 

U 

Ubbelohde, fractional combustion 
of hydrogen, 200 



Vogel, solubility of acetylene, 250; 
phosphine in crude acetylene, 357 



420 



INDEX OF AUTHORS' NAMES 



Voigt, confining liquid in gasometers, 

26 

de Voldere, combustion of gases, 127 
Volhard, determination of silver, 289 

W 

Wagner, determination of nitrous 

oxide, 214 

Wallis, detection of cyanogen, 265 
Watts, reduction of oxides of nitro- 
gen by mercury, 393 
Weil, detection of ozone, 172 
Weiskopf, determination of carbon 
monoxide with iodine pentoxide, 

235 

White, formation of oxides of nitro- 
gen in combustion pipette, 152 

Wild, detection of ozone, 172 

Wilfarth, determination of nitric 
oxide, 222 

Winkler, Clemens, gas sampling tube, 
i; gas burette, 70; absorption ap- 
paratus, 124; combustion pipette, 
147; platinum combustion tube, 
155; palladium asbestos, 193; 



fractional combustion with palla- 
dium asbestos, 194; cuprous chlo- 
ride, 232; determination of hydro- 
gen chloride, 289 

Winkler, L. W., solubility of oxygen, 
158; solubility of hydrogen, 181; 
solubility of carbon monoxide, 
226 

Witzeck, solubility of carbon oxy- 
sulphide, 278; determination of 
carbon oxysulphide, 279 

Wohl, molecular volumes of certain 
gases as influencing combustion 
analysis, 139 

Wolff, absorption tube, 227; hydro- 
gen sulphide in crude acetylene, 
367 

Wurster, detection of ozone, 171, 174 



Young, determination of sulphur 
in coal gas, 327 



Zenghelis, detection of hydrogen, 182 



INDEX OF SUBJECTS 



Absolute humidity, 371 
Absorbing power, analytical, of re- 
agents, 65 

Absorbing power of a reagent, de- 
termination of, 65 
Absorption apparatus for use with 

large volumes of gas, 122 
Absorption apparatus, Winkler, 124 

Winkler-Dennis, 125 
Absorption of gases with Hempel 

pipettes, 6 1 
Absorption of oxygen with alkaline 

pyrogallol, 161 
Absorption pipette, double, for liquid 

reagents, Hempel, 56 
simple, for liquid reagents, 

Hempel, 53 

double, for solid and liquid re- 
agents, Hempel, 58 
simple, for solid and liquid re- 
agents, Hempel, 55 
Hankus, 79 
Heinz, 80 
Nowicki, 80 
Absorption pipettes, efficiency of, 81 

for mercury, 96 
Acetylene, 250 

absorption of, 251 

amount of phosphine in crude, 

357 

commercial, analysis of, 356 
commercial, impurities in, 355 
determination of ammonia in, 
356 



determination of, by absorp- 
tion with cuprous chloride, 
252 

determination of, by absorp- 
tion with fuming sulphuric 
acid, 252 

determination of, by combus- 
tion, 251 

determination of carbon mon- 
oxide in, 369 

determination of hydrogen in, 
356 

determination of oxygen and 
nitrogen in, 369 

determination of phosphine in, 
357 

determination of methane in, 

369 

determination of silicon hydride 
in, 368 

determination of sulphur in, 367 

from calcium carbide, deter- 
mination of yield of, 363 

from pure calcium carbide, 
volume of, 363 

generation of, from calcium car- 
bide, 361 

separation of, from ethylene, 249 

solvents for, 250 
Air (see Atmospheric air) 
Ammonia, 224 

detection of, 224 

detection of, by Nessler's re- 
agent, 224 

determination of, 224 



421 



422 



INDEX OF SUBJECTS 



Ammonia in acetylene, determina- 
tion of, 356 

Ammonia nickel cyanide, prepara- 
tion of solution of, 256 
Ammoniacal silver solution, prepara- 
tion of, 249 

Amylacetate lamp, 307 
Analyses with Hempel apparatus, 
accuracy of, 67 
by combustion, 147 
by explosion, 141 
by explosion, proportion of gases 

in, 143 
with water as the confining 

liquid, 51 

Analytical absorbing power of re- 
agents, 65 

Anderson's apparatus for determina- 
tion of carbon dioxide in air, 387 
Apparatus, absorption, for use with 

large volumes of gas, 122 
absorption, Winkler, 124 
absorption, Winkler-Dennis, 125 
connection of, 113 
construction of, 113 
for analysis with water as con- 
fining liquid, 51 
for exact analysis over mercury, 

Hempel, 90 
mounting of, 114 
Orsat, 78 

without stopcocks, Hempel, 99 
Aqueous vapor, tension of, 411 
Argon, 213 

group, gases of, 213 

group, separation of nitrogen 

from, 209, 212 

Arrangement of laboratory, 49 
Arsine, 291 

detection of, 293 
reaction of, with silver nitrate, 
292 



Asbestos, palladium, preparation of, 

195 
Aspirator, glass bottle, 7 

rubber bulb, 7 

steam, 8 

water suction pump, 8 
Atmospheric air, analysis of, 370 

collection of samples of, 3 

composition of, 370 

detection of ozone in, 1 78 

determination of carbon dioxide 
in, 376 

determination of moisture in, 

37i 

determination of nitrites in, 222 
examination of, 370 
removal of oxygen from large 

volume of, 229 
Atomic weights, 405 
August psychrometer, 375 
Autolysator for determination of 

carbon dioxide, 302 
Automatic flue gas analysis, 299 

gas calorimeter, 354 
Average sample, collection of, 5 

B 

Baroscope, gas, Bodlander, 40 
Bending capillary tubing, 114 
Benzene, 253 

absorption of, by alcohol, 253 
absorption of, by bromine water, 

255 
absorption of, by nickel solution, 

255 

absorption of, by paraffin oil, 254 
determination of, 253 
determination of, as dinitro- 

benzene, 254 

determination of, in coal gas, 312 
separation of, from ethylene, 

250, 259 



INDEX OF SUBJECTS 



423 



Benzoic acid for calorimetry, 341 
Blast furnace gas, 306 

analysis of, 330 

Blast lamp for glass blowing, 113 
Bleaching powder, evaluation of, 

with nitrometer, 401 
Bodlander gas baroscope, 40 
Bomb, Mahler, description of, 331 

preparation of, 337 
Boyle, Law of, 33 
British thermal unit, 346 
Bunte gas burette, 74 
Burette, gas, Bunte, 74. 

gas, Hempel simple, 51 

gas, Honigmann, 72 

Hempel, method of jacketing, 67 

modified Winkler, 70 

with correction tube, Hempel, 

9i 

Butylene, separation of, from ethy- 
lene, 250 



Calcium carbide, sampling of, 356 
Calorimeter, description of, 335 

radiation correction for, 343 

water equivalent of, 340 

Junkers gas, 347 

Junkers gas, manipulation of, 

35i 

Junkers gas, preparation of, 349 
Calorimeters, 331 
Candle, sperm, 307 
Capillary tube, capacity of, per 

linear centimeter, 62 
dimensions of, 51, 53, 62 
method of bending, 114 
Carbon bisulphide, separation of, 

from carbon oxysulphide, 279 
Carbon dioxide, 225 

absorption of, by potassium 
hydroxide, 225 



amount of, in flue gas, 295 

determination of, 225 

determination of, in atmospheric 
air, by Anderson method, 387 

determination of, in atmospheric 
air, by Hesse method, 377 

determination of, in atmospheric 
air, by Pettersson-Palmqvist 
method, 382 

determination of, in coal gas, 311 

determination of, in flue gas, 297 

determination of, in sodium 
carbonate, 403 

recorder, 299 

relation of, to oxygen in air, 377 
Carbon monoxide, 226 

absorption of, 231 

absorption of, by cuprous chlo- 
ride, 233 

colorimetric determination of, 

237 

detection of, 226 

detection of, by blood spectrum, 
226 

detection of, in blood, 227, 231 

detection of, with iodine pent- 
oxide, 231 

determination of, 231 

determination of, by fractional 
combustion, 239 

determination of, in acetylene, 

369 ^ 

determination of, in coal gas, 313 

determination of, in flue gas, 298 

determination of, with iodine 

pentoxide, 235 
Carbon oxysulphide, 277 

absorbents for, 278 

detection of, 279 

determination of, 279 

separation of, from carbon bi- 
sulphide, 279 



424 



INDEX OF SUBJECTS 



Carbon oxysulphide, separation of, 

from hydrogen sulphide, 279 
Change of temperature, error caused 

by, 67 

Charles, Law of, 33 
Chlorine, 284 

determination of, 285 
determination of, in presence of 

carbon dioxide, 285 
determination of, in presence of 

hydrochloric acid, 288 
Chloride of lime, evaluation of, with 

nitrometer, 401 
Chromous chloride, absorption of 

oxygen by, 169 

Coal briquet, preparation of, 333 
Coal, example of determination of 

heating value of, 345 
preparation of sample of, 333 
Coal gas, 306 

apparatus for analysis of, 310 
complete examination of, 306 
constituents of, 306 
determination of absorbable 

gases in, 310 

determination of benzene in, 312 
determination of carbon dioxide 

in, 311 

determination of carbon mon- 
oxide in, 313 
determination of cyanogen in, 

263 ^ 

determination of heavy hydro- 
carbons in, 312 
determination of naphthalene in, 

318 ^ 

determination of nitrogen in, 317 
determination of oxygen in, 313 
determination of specific gravity 

of, 309 

determination of total sulphur 
in, 319 



Drehschmidt-Hempel method 

for sulphur in, 320 
gas- volumetric analysis of, 309 
illuminating power of, 307 
Referees' method for sulphur in, 

320 
simultaneous determination of 

hydrogen and methane in, 314 
simultaneous determination of 

methane and ethane in, 314 
successive determination of hy- 
drogen, methane and nitrogen 

in, 315 
volumetric determination of 

sulphur in, 327 
Collection of gases, i 

dissolved in liquids, by Hoppe- 

Seyler method, 19 
dissolved in liquids, by Tiemann 

and Preusse method, 16 
Collection of gas from mercury 

pump, 13 
Collection of gases from mineral 

waters, 15 

from reactions in sealed tubes, 21 
from springs, 15 
Combustible substance, standard, 

for calorimeter, 341 
Combustion, analysis by, 147 

determination of gases by, 141 
fractional, of hydrogen, 191 
fractional, of hydrogen, with 

copper oxide, 198 
fractional, of hydrogen, with 

palladium-black, 196 
fractional, of hydrogen, with 

platinum or palladium asbes- 
tos, 192 

Combustion of gases, 127 
First Case, 130 
Second Case, 133 
Third Case, 134 



INDEX OF SUBJECTS 



425 



Combustion pipette, Dennis, 147 
formation of oxides of nitrogen 

in, 152 

Combustion, simultaneous, of hydro- 
gen, methane and carbon mon- 
oxide, 244- 

with Drehschmidt tube, 154 
with electrically heated spiral, 

147 
with platinum capillary tube, 

154 
Confining liquid, running down of, 

68 

water, saturation of, 59 
Connection of apparatus, 113 
Connection of gas pipette with 

burette, 62, 64 
Connections, rubber, 114 
Construction of apparatus, 113 
Copper, absorption of oxygen by, 

1 66 

Correction tubes for Hempel bu- 
rettes, 91 
Cuprous chloride, preparation of 

acid solution of, 232 
preparation of ammoniacal solu- 
tion of, 232, 233 
Cyanogen, 262 

amount of, in illuminating gas, 

265 

detection of, 262 
detection of, in presence of hy- 
drogen cyanide, 265 
determination of, 263 
determination of, in coal gas, 263 
determination of, in presence of 
hydrogen cyanide, 265 

D 

Dennis combustion pipette, 147 

manipulation of, 149 
Dennis spiral absorption pipette, 81 



Densities of gases, theoretical, 406 
Determination of gases, 158 
Distillation of mercury, 119 
Double absorption pipette for solid 

and liquid reagents, Hempel, 58 
Double absorption pipettes, Hempel, 

56 

Drawing off of gas sample, i 
Drehschmidt tube, combustion with, 

154 



Efficiency of absorption pipettes, 81 
Enamelled rubber tubing, 1 14 
Error due to change of temperature 

during analysis, 67 
Ethane and methane, possible errors 

in combustion of, 131 
simultaneous determination of, 

in coal gas, 314 
Ethylene, 248 

absorption of, by bromine, 249 
absorption of, by fuming sul- 
phuric acid, 249 
determination of, 249 
determination of, in presence of 

acetylene, 249 
separation of, from benzene, 250, 

259- 

separation of, from butylene, 250 
Exact analysis over mercury, Hempel 

apparatus for, 90 
Exact apparatus without stopcocks, 

Hempel, 99 
Explosion, analysis by, 141 

analysis, proportion of gases in, 

143 

pipette for exact analysis, 146 
pipette for technical analysis, 

141 

Extraction of gases from minerals, 
21 



426 



INDEX OF SUBJECTS 



Ferrous salts, absorption of oxygen 

by, 1 68 
Filling of gas pipettes with liquid 

reagents, 57 

Fittings of the laboratory, 49 
Flue gas, amount of carbon dioxide 

in, 295 

Flue gas, analysis of, 295, 297 
automatic analysis of, 299 
average sample of, 296 
sampling of, 2 
Fluorine, determination of, 280 

determination of, in presence of 

carbon dioxide, 280 
determination of, in teeth, 284 
Formation of oxides of nitrogen in 

combustion pipette, 152 
in explosion analysis, 144 
Fractional combustion of hydrogen, 

191 

with copper oxide, 198 
with palladium-black, 196 
with platinum or palladium 

asbestos, 192 
Friedrichs spiral gas washing bottle, 

123, 124 
Fuel gas, 306 

Fuels, liquid and gaseous, determina- 
tion of heating value of, 347 
solid, determination of heating 

value of, 331 

Fuming sulphuric acid, absorption 
of heavy hydrocarbons by, 247 
pipette for, 247 
Furnace gases, sampling of, i 



Gas baroscope, Bodlander, 40 
Gas calorimeter, automatic, 354 

Junkers, 347 

Junkers, manipulation of, 351 



Junkers, preparation of, 349 
Gas, determination of specific gravity 

of, 44 

Gaseous fuels, determination of heat- 
ing value of, 347 

hydrocarbons and nitrogen, de- 
termination by combustion, 
136 

hydrocarbons, identification of, 

' by combustion, 138 
Gases, combustion of, 127 

determinable by combustion, 
127, 128 

determination of, 158 

determination of, by combus- 
tion, 141 

dissolved in liquids, collection of, 
by Hoppe-Seyler method, 19 

dissolved in liquids, collection 
of, by Tiemann and Preusse 
method, 16 

from mineral waters, collection 
of, 15 

from reactions in sealed tubes, 
collection of, 21 

from springs, collection of, 15 

measurement of, 33 

properties of, 158 

proportion of, in analysis by ex- 
plosion, 143 

readily soluble, determination 
of, 70 

variations in gram-molecular 

volumes of, 139 

Gas from mercury pump, collection 
of, 13 

generator, oxyhydrogen, 145 

measurement of large samples 
of, 28 

meter, 28 

methods for determining quan- 
tity of, 33 



INDEX OF SUBJECTS 



427 



Gasometers, 23 
Gas refractometer, 304 
Gas volume, reduction of, to stand- 
ard conditions, 33 

tables for reduction of, 407 
Gas volumeter, Lunge, 37 

Lunge, objections to, 39 
Gas volumetric analysis of coal gas, 

309 
Gas washing bottle, spiral, 123, 

124 

Generator, oxyhydrogen, 145 
Glass blowing, 113 

blast lamp for, 113 
glass tubing for, 113 
Gram-molecular volumes, variations 

in, 139 

Gross heating value, 352, 354 
Gun cotton, analysis of, 393 

H 

Hankus absorption pipette, 79 
Heating value of coal, example of 

determination of, 345 
of fuel, combustion of sample, 

339 

of fuel, determination of, 331 
of gaseous fuels, total, gross and 

net, 352, 354 

of liquid and gaseous fuels, de- 
termination of, 347 
Heavy hydrocarbons, 246 
absorption of, 246 
determination of, in coal gas, 312 
Hefner lamp, 307 
Heinz absorption pipette, 80 
Helium, 213 
Hempel apparatus, accuracy of 

analyses with, 67 
for exact analysis over mercury, 

90 
portable, 69 



Hempel burettes with correction 

tubes, 91 
Hempel double absorption pipette 

for liquid reagents, 56 
for solid and liquid reagents, 58 
Hempel exact apparatus without 

stopcocks, 99 
Hempel gas burette, method of 

jacketing, 67 
Hempel pipette, absorption of a gas 

with, 6 1 
Hempel simple absorption pipettes, 

53 

Hempel simple gas burette, 51 
Hesse method, collection of samples 
of air, 379 

for carbon dioxide in air, 377 

solutions used in, 378 
Honigmann gas burette, 72 
Hydrocarbons, classes of, determin- 
able by combustion, 127 

gaseous, and nitrogen, deter- 
mination by combustion, 136 

gaseous, identification of, by 
combustion, 138 

heavy, 246 

heavy, absorption of, 246 
Hydrogen. 181 

absorption of, by palladium- 
black, 188 

and methane, simultaneous de- 
termination of, in coal gas, 314 

detection of, 181, 182 

determination of, by absorption, 
182 

determination of, by explosion, 
186 

determination of, in presence of 
methane, 242 

determination of, with combus- 
tion pipette, 187 

fractional combustion of, 191 



428 



INDEX OF SUBJECTS 



Hydrogen, fractional combustion of, 
with copper oxide, 198 

fractional combustion of, with 
palladium-black, 196 

fractional combustion of, with 
platinum or palladium asbes- 
tos, 192 

in acetylene, determination of, 
356 

methane and nitrogen, successive 
determination of, in coal gas, 

3i5 
Hydrogen chloride, 289 

determination of, 289 
Hydrogen cyanide, 269 
detection of, 269 
detection of, in presence of 

cyanogen, 267 
determination of, 269 
determination of, in presence of 

cyanogen, 267 

Hydrogen dioxide, detection of, in 
presence of ozone and nitrogen 
tetroxide, 171, 175 
evaluation of, with nitrometer, 

401 
reagents for detection of, 171, 

172 
Hydrogen peroxide (see Hydrogen 

dioxide) 
Hydrogen pipette, 144 

for exact analysis, 147 
Hydrogen sulphide, 270 
detection of, 271 
determination of, 272 
separation of, from carbon oxy- 

sulphide, 279 
Hygrodeik, 375 

Humidity, absolute and relative, 371 
of the atmosphere, determina- 
tion of, 371 
relative, calculation of, 374 



Identification of gaseous hydrocar- 
bons by combustion, 138 
Ignition wire, 337 
Illuminating gas, 306 

amount of cyanogen in, 265 

analysis of, 306 

determination of cyanogen in, 

328 
determination of heating value 

of, 347 
determination of illuminating 

power of, 307 
determination of naphthalene in, 

3i8 
determination of specific gravity 

of, 309 
determination of total sulphur 

in, 319 

volumetric analysis of, 309 
Illuminating power, computation of, 

308 

of coal gas, determination of, 307 
Impurities in commercial acetylene, 

355 

Induction coil, 144 
International atomic weights, 405 
Iodine pentoxide, detection of carbon 

monoxide with, 231 
determination of carbon mon- 
oxide with, 235 
Iron ignition wire, 337 



Jacketing of Hempel gas burette, 67 
Junkers automatic gas calorimeter, 

354 

gas calorimeter, 347 
gas calorimeter, manipulation 

of, 35i 
gas calorimeter, preparation of, 

349 



INDEX OF SUBJECTS 



429 



Krypton, 213 



Laboratory, arrangement of, 49 

Large samples of gas, measurement 
of, 28 

Laws concerning combustion of 
gases, 127 

Law of Boyle, 33 

Law of Charles, 33 

Liquid fuels, determination of heat- 
ing value of, 347 

Liter weights of gases, 406 

Lubricant for stopcocks, preparation 
of, 115 

Lubrication of stopcocks, 115 

Lunge gas volumeter, 37 
nitrometer, 397 
ureometer, 397 

M 

Mahler bomb, description of, 331 
Marsh gas (see Methane) 
Measurement of gases, 33 

of large samples of gas, by 

bottle and cylinder, 28 
of large samples of gas, by gas 

meter, 28 

of large samples of gas, by rota- 
meter, 32 
Mercury, distillation of, 119 

impurities in commercial, 117 

purification of, 117 

pump, 8 

pump, collection of gas from, 

13 

pump, description of, 9 
pump, method of working, 12 
Metaphosphoric acid as lubricant 
for stopcocks, 116 



Methane, 240 

and ethane, possible errors in 
combustion of, 131 

and ethane, simultaneous deter- 
mination of , 131, 203 

and ethane, simultaneous de- 
termination of, in coal gas, 
3i4 

and hydrogen, simultaneous de- 
termination of, in coal gas, 

3H 

combustion of, in Dennis pipette, 
246 

determination of, 241 

determination of, by combus- 
tion, 241 

determination of, in presence of 
hydrogen, 242 

hydrogen and nitrogen, succes- 
sive determination of, in coal 
gas, 315 

in acetylene, determination of, 

369 

Minerals, extraction of gases from, 21 
Mineral waters, collection of gases 

from, 15 

Modified Winkler gas burette, 70 
Moisture in the atmosphere, deter- 
mination of, 371 
Mounting of apparatus, 114 

N 

Naphthalene, 260 

determination of, 260 

determination of, in coal gas, 318 

for calorimeter, 342 
Natural gas, 306 
Neon, 213 

Net heating value, 352, 354 
Nickel cyanide, ammonia, prepara- 
tion of solution of, 256 
Nitric acid esters, analysis of, 393 



43 



INDEX OF SUBJECTS 



Nitric oxide, 217 

absorption of, 219 
combustion of, 219 
detection of, 218 
determination of, 219 
volumetric determination of, 

220 

Nitrites in the atmosphere, deter- 
mination of, 222 
Nitrogen, 206 

absorption of, 207 
and gaseous hydrocarbons, de- 
termination by combustion, 
136 

and oxygen in acetylene, deter- 
mination of, 369 
determination of, in coal gas, 

3i7 
determination of, in gas mix^ 

tures, 317 
oxides, formation of, in explosion 

analysis, 144 
separation of, from argon group, 

209, 212 
Nitrogen peroxide (see Nitrogen 

tetroxide) 
Nitrogen tetroxide, 223 

detection of, in presence of ozone 
and hydrogen dioxide, 171, 

175 
reagents for detection of, 171, 

172 

Nitrometer, 393 
Lunge, 397 

Nitroglycerine, analysis of, 393 
Nitrous acid, determination of sul- 
phur dioxide in presence of, 276 
Nitrous oxide, 213 

combustion of, 214 
detection of, 213 
determination of, 214 
Nowicki absorption pipette, 80 



Orsat apparatus, 78 

objections to usual form of, 79, 

84,85 
Orsat-Dennis apparatus, 85 

accuracy of, 89 

Oxides of nitrogen, formation of, in 
combustion pipette, 152 

formation of, in explosion analy- 
sis, 144 

reduction by mercury, 393 
Oxygen, 158 

and nitrogen in acetylene, de- 
termination of, 369 

determination of, 158 

determination of, by absorption, 
1 60 

determination of, by combus- 
tion, 159 

determination of, in coal gas, 313 

determination of, in flue gas, 298 

determination of, in presence of 
acetylene, 253 

determination of, in presence of 
hydrogen sulphide and carbon 
dioxide, 169 

determination of, with alkaline 
pyrogallol, 160 

determination of, with copper 
eudiometer, 159 

removal of, from air, 229 
Oxyhydrogen gas generator, 145 

removal of ozone in, 146 
Ozone, 170 

detection of, 170 

detection of, in presence of nitro- 
gen tetroxide and hydrogen 
dioxide, 171, 174 

determination of, 179 

formation of, in hydrogen flame, 
175 



INDEX OF SUBJECTS 



431 



Ozone, in atmospheric air, detection 

of, 178 
production of, by action of 

sulphuric acid upon barium 

dioxide, 177 
production of, by silent electric 

discharge, 176 
production of, by slow oxidation 

of phosphorus, 178 
reagents for detection of, 171, 

172 
removal of, in oxyhydrogen gas, 

146 



Palladium asbestos, preparation of, 

iQ5 

Palladium-black, absorption of hy- 
drogen by, 1 88 
preparation of, 196 
regeneration of, 189 
Palladium, colloidal, preparation of, 

182 

solution for absorption of hydro- 
gen, 183 
tube, determination of volume of 

oxygen in, 189 
Pentane lamp, 307 
Pettersson-Palmqvist method for 

carbon dioxide in air, 382 
Phosphine, 290 

absorption of, by sodium hypo- 

chlorite, 362 
amount of, in crude acetylene, 

357 

detection of, 291 
determination of, 291 
determination of, in presence of 

acetylene, 291 
in acetylene, determination of, 

357 



Phosphorus, gas pipette for, 56 

in solution, absorption of oxygen 

by, 1 66 

Phosphorus pentoxide, as dehydrat- 
ing agent, n 
impurities in, n 
Phosphorus, preparation of thin 

sticks of, 164 
solid, absorption of oxygen by, 

163 

Photometric units, 307 
Photometer, Bunsen, 308 
Photometry, 307 

Picric acid, determination of naph- 
thalene with, 260 
Pintsch gas, 306 
analysis of, 329 
composition of, 329 
Pipette, absorption, double, Hempel, 

56 
absorption, for liquid reagents, 

simple, Hempel, 53 
absorption, for solid and liquid 

reagents, simple, Hempel, 55 
absorption, Hankus, 79 
absorption, Heinz, 80 
absorption, mercury, 96 
absorption, Nowicki, 80 
combustion, Dennis, 147 
combustion, Dennis, manipula- 
tion of, 149 
combustion, formation of oxides 

of nitrogen in, 152 
explosion, for exact analysis, 

146 
explosion, for technical analysis, 

141 
for phosphorus, of brown glass, 

165 
for solid and liquid reagents, 

double, Hempel, 58 
gas, for phosphorus, 56 



432 



INDEX OF SUBJECTS 



Pipette, gas, method of fastening to 

stand, 54 
Hempel, absorption of a gas 

with, 6 1 
hydrogen, 144 
hydrogen, for exact analysis, 

147 

spiral absorption, Dennis, 81 
stand for, 54 

Platinum capillary tube, combus- 
tion with, 154 

Portable Hempel apparatus, 69 
Potassium hydroxide, strength of 

solution of, 225 

Potassium permanganate, standard- 
ization of, with nitrometer, 400 
Press for coal briquet, 334 
Producer gas, 306 

analysis of, 330 

Properties of various gases, 158 
Proportion of gases in analysis by 

explosion, 143 
Propylene, 250 
Psychrometer, August, 375 
whirling, 372 

whirling, manipulation of, 373 
Pump, mercury, 8 

mercury, method of working, 12 
Purification of mercury, 117 

by concentrated sulphuric acid 
and mercurous sulphate, 117, 
119 

by distillation, 117, 119 
by nitric acid, 118 
Pyrogallol, alkaline, preparation of, 

1 60 

Pyrolusite, evaluation of, with ni- 
trometer, 402 



Quantity of a gas, methods for de- 
termining, 33 



Radiation correction, 343 
Reagents, analytical absorbing power 

of, 65 

Recorder of carbon dioxide, 299 
Reduction of gas volumes, 33 

of gas volume, tables for, 407 
"Referees' Test," for total sulphur, 

3i9 

Refractometer, gas, 304 
Relative humidity, 371 

calculation of, 374 
Rotameter, 32 
Rubber bulb aspirator, 7 

connections, 114 

tubing, enamelled, 114 

tubing, objections to, for con- 
nections, 2 
Running down of confining liquid, 68 



Saltpeter, analysis of, 393 

Sample, drawing off of, i 

Samples of gas, measurement of 
large, 28 

Sampling of air, 3 
of flue gas, 2 
of furnace gases, i 
of gas from gas mains, 2 
tube for furnace gases, i 
tube for furnace gases, Wink- 

ler, i 

tube for gas from mains, 3 
tube, Huntly, 5 
tubes for air, 3 
tubes, glass, with stopcocks, 4 

Saturation of confining water, 59 

Sealed tubes, collection of gases from 
reactions in, 21 

Silicon hydride in acetylene, deter- 
mination of, 368 



INDEX OF SUBJECTS 



433 



Silicon tetrafluoride, 290 
Silver solution, ammoniacal, prepara- 
tion of, 249 
Simple absorption pipette for liquid 

reagents, Hempel, 53 
for solid and liquid reagents, 

Hempel, 55 
Sodium carbonate, analysis of, with 
nitrometer, 403 

hypochlorite, absorption of 

phosphine by, 362 
hyposulphite, absorption of 

oxygen by, 168 
hyposulphite, reaction of, with 

oxygen, 168 
Solid phosphorus, absorption of 

oxygen by, 163 

Soluble gases, determination of read- 
ily, 70 

Specific gravity of coal gas, determin- 
ation of, 309 

Specific gravity of a gas, determina- 
tion of, by method of Bunsen, 44 
by method of Pannertz, 44 
by method of Schilling, 44 
Spectrum of blood, 227 

of carbon monoxide hsemoglobin, 

227 

Sperm candle, 307 
Spiral absorption pipette, 81 

gas washing bottle, 123, 124 
Springs, collection of gases from, 

IS 
Standard combustible substances for 

calorimeter, 341 
Stands for gas pipettes, 54 
Stibine, 293 
Stopcocks, 115 

lubrication of, 115 
Storage of gases, i 
Sucrose for calorimeter, 341 



Suction pump and rubber bulb aspi- 
rator, 8 

brass, 8 

water, 8 

Sulphur, determination of, in acety- 
lene, 367 

determination of, in coal gas, 319 

in acetylene, source of, 367 

in coal gas, Drehschmidt-Hempel 
method for, 320 

in coal gas, Referees' method for, 
320 

in coal gas, volumetric method 

for, 327 
Sulphur dioxide, 273 

determination of, 274 

determination of, in flue gas, 299 

determination of, in presence of 

nitrous acid, 276 

Sulphuric acid, fuming, absorption 
of heavy hydrocarbons by, 247 

fuming, pipette for, 247 



Ten-bulb tube, Lunge, 359 

Tension of aqueous vapor, table of, 

411 

Theoretical densities of gasesj 406 
Topler pump, collection of gas from, 

13 

description of, 9 
method of working, 12 
Total heating value, 352 
Tubes, sampling, for furnace gases, i 

sampling, of glass, 3, & 5 
Tubing, capillary, method of bending, 

114 
rubber, enamelled, 114 

U 
Ureometer, Lunge, 397 



434 



INDEX OF SUBJECTS 



Vapor, tension of aqueous, 411 
Ventilation, effects of poor, 376 
Volumeter, gas, Lunge, 37 

W 

Water equivalent of calorimeter, 340 
example of determination of, 342 

Water gas, 306 

suction pump, 8 

Weight of gas, determination of, 
from its pressure, 40 



Weights of one liter of different gases, 
406 

Wet and dry bulb thermometers, 371 

Whirling psychrometer, 372 
manipulation of, 373 

Winkler absorption apparatus, 124 

Winkler-Dennis absorption appara- 
tus, 125 

W'inkler gas burette, 70 



X 



Xenon, 213 



'HpHE following pages contain advertisements of a 
few of the Macmillan books on kindred subjects 



General Chemistry, Theoretical and Applied. 



BY J. C. BLAKE, 

Head of the Department of Chemistry and Chemical Engineering in 
the Agricultural and Mechanical College of Texas 

Preparing 

This book is a combination of theoretical, descriptive and 
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of such information being placed on the voluntary observations 
of the student while in the laboratory or on his collateral reading. 

The Laboratory Exercises, bound separately, which accompany 
the book include experiments of a theoretical nature, together 
with work in inorganic synthesis, qualitative analysis of simple 
mixtures, and simple tests of technical importance. 



PUBLISHED BY 

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Methods of Organic Analysis 

BY HENRY C. SHERMAN, PH.D. 

Professor of Food Chemistry in Columbia University. 

Author of "Chemistry of Food and Nutrition." 

Second Edition Rewritten and Enlarged. 

Illustrated, Cloth, 8vo, $2.40 net 

SOME REVIEWS 

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Journal of the American Chemical Society. 

Commendable features are: the free use of references in the form 
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While this book is not primarily intended for medical students or 
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Medical Record. 



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A College Text-Book on Quantitative Analysis 

BY HERBERT RAYMOND MOODY, PH.D. 

Associate Professor of Analytical and Applied Chemistry in the 
College of the City of New York 

Cloth, 8vo, 165 pages, $1.25 net 

With the ordinary manual the student is inclined to proceed 
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CONTENTS 

Section I. GRAVIMETRIC ANALYSIS 3 

Section II. ELECTROLYTIC ANALYSIS 83 

Section III. VOLUMETRIC ANALYSIS 95 

INTERNATIONAL ATOMIC WEIGHTS 156 

LOGARITHMS 157 



PUBLISHED BY 

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A Course in Qualitative Chemical Analysis 

BY CHARLES BASKERVILLE, PH.D., F. C. S. 

Professor in the Department of Chemistry, 

College of the City of New York 

AND 

LOUIS J. CURTMAN, PH.D. 

Instructor in the Department of Chemistry, 
College of the City of New York 

Cloth, 8vo, 200 pages, $1.40 net 

. The essential features of this book may be seen from the plan which 
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frequent practice of blindly following directions. 



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