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Full text of "Practical agricultural chemistry for elementary students, adapted for use in agricultural classes and colleges"

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PRACTICAL 

AGRICULTURAL CHEMISTRY 

FOR ELEMENTARY STUDENTS 
ADAPTED FOR USE IN AGRICULTURAL CLASSES AND COLLEGES 

BY 

J. BERNARD COLEMAN, A.R.C.Sc, F.I.G. 

HEAD OF THE CHEMICAL DEPARTMENT, SOUTH WESTERN POLYTECHNIC, CHELSEA, S.W 
FORMERLY LECTURER ON THE PRINCIPLES OF AGF&CltLi^ltB! *. .* , 

IN THE UNIVERSITY COLLEGE, NOTTINGHAM- • *• " • • 



« • * ••••••• "• •• • • 

and . •• ; : :• . :• . •*.•: ; 



FRANK T. ADDYMAN, B.Sc. (Lond.), F.I.C. 

CONSULTING CHEMIST, FORMERLY ASSISTANT IN THE LABORATORY OF 

THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND 

LATE PRINCIPAL OF THE LANCASHIRE COUNTY SCHOOL OF AGRICULTURE 



NEW IMPRESSION 



LONGMANS, GREEN, AND CO. 

39 PATERNOSTER ROW, LONDON 

NEW YORK, BOMBAY, AND CALCUTTA 

1913 

All rights reserved 



.• • 8 .•• 






•••iflN LIBRARY-AGRICULTURE DEFT. 



PREFACE 



The course of instruction described in this book was origi- 
nally arranged for the students of agriculture at University 
College, Nottingham. 

It is now largely used by the teachers and students of 
the numerous agricultural classes established throughout 
the country. 

It is suited to the requirements of those commencing 
the study of Agriculture. 

The experiments are so arranged as to give a scientific 
acquaintance with the substances commonly met with on 
the farm. 

The matter is divided into the following sections :— 

Section I. treats of simple chemical manipulation and 
the preparation of apparatus. 

Section II. describes the preparation and properties of 
the constituents of air and water. 

Section III. contains a number of experiments illus- 
trating the properties of soils, manures, feeding materials, 
and dairy produce. 

Section IV. gives the chemical tests for the bodies 
commonly occurring in soils, manures, and ashes of plants, 
and describes the qualitative analysis of these bodies. 

It will be seen that only those substances are treated of 



469651 



iv PRACTICAL AGRICULTURAL CHEMISTRY 

that enter into the composition of the various agricultural 
products. For the analyses of minerals and other occa- 
sional constituents found in the earth, works on qualitative 
analysis should be consulted. 

Section V. contains a list of apparatus and chemicals 
lequired for performing the experiments described in this 
book, together with instructions for preparing the various 
solutions. 

After working through this course, students are recom- 
mended to consult Addyman's ' Agricultural Analysis.' 

Our acknowledgments are due to Professor F. Clowes, 
D.Sc. (Lond.), for permission to use woodcuts and other 
material from his text-book on Qualitative Analysis. 

In the preparation of the present edition, the whole of 
the existing matter has been carefully revised. Some por- 
tions have been re-written and important additions have 
been made. 

J. B. C. 
F. T. A. 

London : Oct. 1908. 



CONTENTS 



SECTION I 

CHEMICAL MANIPULATION AND 
APPARATUS 

PARA- PAG1 
GRAPH 

The Bunsen Burner i i 

The Spirit Lamp 2 2 

The Blowpipe 3 2 

The Table Blowpipe .4 3 

Cutting and Bending Glass Tube and Rod . 5 3 

Making Closed Tubes 6 4 

Mounting Platinum Wire 7 4 

Boring Corks . . 8-9 5 

Fitting up Wash-bottle 10 5 

Solution 11 6 

Evaporation ....... 12 7 

Steam Bath . . . . . ... 13 8 

Crystallisation • 14 8 

Precipitation . 15 8 

Filtration 16, 17 9 

Washing Precipitates 18-21 9 

Drying Precipitates 22 10 

Ignition . 23 11 

Fusion 24 11 

Sublimation 2 S " 

Flame Colorations • . 26 u 

Borax Bead 27 12 

Use of Test-papers 28 12 



Vi PRACTICAL AGRICULTURAL CHEMISTRY 

SECTION II 
THE CONSTITUENTS OF AIR AND WATER 

PARA- PAGE 
GRAPH 

Air 29 33 

Oxygen . 3°-34 *3 

Nitrogen 35" 3§ J 5 

Carbon Dioxide 39-42 16 

Ammonia 43-4^. 18 

The Atmosphere 47-49 l 9 

Water 50 20 

Hydrogen, Preparation and Properties . 51-55 20 

Water, Experiments on . » 56-60 22 



SECTION III 

EXPERIMENTS ON SOILS, MANURES, 
FEEDING MATERIALS, AND DAIRY 
PRODUCE 

Soils 61-67 26 

Manure 68 28 

Manures, Lime 69-75 28 

Manures, Potash 76 31 

Manures, Phosphatic 77-83 31 

Manures, Nitrogenous 84-87 33 

The Mixing of Manures 88-90 35 

Testing Manures 91-98 36 

Compound Manures 99-106 38 

Oil-Cakes 107-117 41 

Grass and Hay . 118 123 44 

Roots 124-129 46 

Cereals 130-132 48 

Milk . . . i33-*39 49 

Butter 140-142 51 

Cheese 143. »44 5* 



CONTENTS vii 



SECTION IV 



QUALITATIVE ANALYSIS OF SOILS 
AND MANURES 

PARA- PACE 
GRAPH 

Introductory Remarks 145-148 53 

General Rules for Working . . . . 149-157 54 

REACTIONS FOR THE METALS 

Aluminium 158-160 55 

Iron 161-172 56 

Manganese 173-177 57 

Calcium 178-181 58 

Magnesium 182-185 59 

Sodium 186-187 59 

Potassium 188-190 60 

Ammonium 191-193 60 

REACTIONS FOR THE ACID-RADICALS 

Sulphate 194 61 

Carbonate 195 61 

Nitrite 196, 197 61 

Nitrate 198-200 62 

Chloride . . 201-203 62 

Phosphate 204-207 63 

Silicate 208-210 63 

Organic Carbon 211,212 64 

Organic Nitrogen 213,214 64 

Organic Chlorine 215 64 

Organic Sulphur 216 65 

TABLES FOR QUALITATIVE ANALYSIS 

Table I. — Preliminary Examination of Solids 

for Metals 217-223 65 

Organic Matter 224-227 66 



Vlll PRACTICAL AGRICULTURAL CHEMISTRY 
Wet Examination for the Metals 

PARA- PAGS 
GRAPH 

Solution of Solids 228, 229 67 

Notes to Table II 230-235 6/ 

Table II.— The Separation of the Metals . 236 68 

Table III.— The Phosphate Precipitate . . 237 70 

Explanation of the Phosphate Table . . 238, 239a 70 
Table IV. — Preliminary Examination for 

Acid-radicals 240-243 71 

Table V. — Further Examination for Acid- 
radicals 244-249 71 

Analysis of Substances Insoluble in Water 

and Acids 250-258 72 

Example of Entry of Analysis in Note-book . 259 74 

SECTION V 

APPARATUS, CHEMICALS, AND 
REAGENTS 

Bench Apparatus . . . . . . 260 76 

Apparatus for Sections L, II., and III. . . 261 77 

Apparatus for General Use .... 262 78 

Reagents and Chemicals 263 79 

Bench Reagents 264 79 

Chemicals for Sections I. and II. . . . 265 80 
Substances for Section III. .... 266 81 
Reagents for Detection of Metals . . . 267 82 
Reagents for Detection of Acid- radicals . 268 83 
Solutions for the Reactions of the Metals 269 84 
Solutions for the Reactions of the Acid- 
radicals 270 84 

Table of the Atomic Weights of the 

Elements 271 85 

Thermometry Scales 272 85 

Weights and Measures 273, 274 86 

INDEX ......... 88 



PRACTICAL 
AGRICULTURAL CHEMISTRY 



SECTION I 

CHEMICAL MANIPULATION AND APPARATUS 

The student whose time is very limited, on wotking through the 
experiments described in this book, may omit those paragraphs marked 
with an asterisk. 

I. The Bunsen Burner. — Where gas can be obtained 
the Bunsen burner (fig. i)will be found the most convenient 
lamp for heating purposes. Before 
use the coal-gas is mixed with air, and 
when ignited burns with a feebly 
luminous flame, which deposits no soot 
when a solid object is held in the 
flame. For this reason the Bunsen 
or some other atmospheric burner is 
nearly always employed for chemical 
work in place of the luminous flame- 
burner. The Bunsen burner (fig. i) 
consists essentially of a gas-jet (#), 
which is surrounded by an outer tube 
(c), in which the air passing through 
two inlets (b) mixes with the gas. 
The mixture of air and gas is burnt at the top of the 
outer tube (c). Over the air-holes fits a ring, which by 
turning round will cut off either wholly or partially the supply 
of air. When the flame is turned down it is necessary to re- 

B 




Fig. i 



'I ^: : './EKAar}CA v L' : AGRICULTURAL CHEMISTRY [2-3 

duce the supply of air, or the gas will take fire below, which 
then gives off unpleasant-smelling products, and may melt 
the rubber tubing attached to the burner. If the burner 
should thus take fire below, at once turn off the gas, reduce 
the air supply by turning the ring, and relight. 

For heating a large surface a * rose-top ' may be used. 
It consists of a metal cap perforated with holes to distribute 
the gas. The cap is slipped on to the top of the burner 
when it is required for use. 

2. The Spirit-lamp. — Where gas is not available the 
spirit-lamp (fig. 2) forms a convenient heating-lamp. Like 

the Bunsen burner the flame is non- 
luminous, and does not smoke; but the 
temperature is not so high, and the 
flame cannot be so conveniently regu- 
lated. It consists of a reservoir con- 
taining methylated spirit, into the neck 
of which passes a wick-holder which 
supports the cotton-wick. When not 
in use the spirit-lamp should be covered 

with the ground-glass cap (a) to prevent evaporation of the 

spirit. 

Special forms of spirit- lamps, known as ' spirit-bunsens,' can 

now be purchased. They burn a mixture of spirit-vapour and air, and 

give a much higher temperature than does the ordinary spirit-lamp. 

3. The Blowpipe. — The mouth blowpipe shown in 
fig. 3 is useful for obtaining a high temperature. On blowing 
a stream of air by means of this apparatus through an ordinary 
luminous flame a small hot flame is obtained. In order to 
produce this effect turn off the air supply in the Bunsen 
burner (fig. 1), so as to obtain the luminous flame. Next 
turn down the gas supply until the flame is nearly two 
inches in height. Now place the jet of the blowpipe just 
over the orifice of the burner and blow a gentle current of 
air into the flame. The flame will then lose its luminosity 
and appear as a finely pointed tongue of flame (fig. 4). In 
the use of the blowpipe the student should practise so as 




4-5] 



THE BLOWPIPE 



to produce a continuous blast. This is acquired by first 
inflating the cheeks with air from the lungs, keeping them 
inflated until the lungs are exhausted of 
air ; then when inhaling — i.e. refilling the 
lungs — the air in the cheeks should be ex- 
pelled gradually, and thus keep the blast 
continuous. After a little practice the stu- 
dent will be able to breathe through the 
nose during blowpipe-work, whilst he is 
employing his cheeks and lungs to keep up 
a steady blast. 

4. For heating large vessels to a high 
temperature the table blowpipe is usually 
used. In this blowpipe the air is forced 
through the flame by means of a. foot-bellows. 
Since both hands are at liberty it is usually 
used in glass -working (paragraphs 5, 6, 
and 7). 

5. Cutting and Bending Glass Tube and 
Rod. — Glass tube (or rod) may readily be cut by first 
making a deep cut with a sharp triangular file, then holding 
the tube on either side of the cut, and finally applying a 




Fig. 3 




strain partly between a pull and a break. The rough edges 
should either be filed or held for a short time in the Bunsen 
burner, so as to fuse the edges, and thus prevent the jagged 
edges from cutting the hands. 

Glass tube (or rod) is readily bent by holding the tube 
in the upper part of a fish-tail burner (fig. 5), constantly 

a 2 



4 PRACTICAL AGRICULTURAL CHEMISTRY [6-7 

rotating the tube so as to heat it uniformly. When the 
glass becomes soft it may be bent at any desired angle. 




Fig. s 

When cold the soot may be wiped off with a duster. If 
bent as described the bend will be rounded and of uniform 
bore throughout. If bent in a Bunsen flame the tube is 
usually flattened out at the bend and very liable to break. 

6. Making Closed Tubes.— Select a piece of glass 
tube about 6 in. long and -^ in. internal diameter. Heat 
it in the middle portion by means of the blowpipe flame. 
When quite soft draw it out, as shown, fig. 6. Next heat 
the portion (a) in the tip of the flame, so that on drawing 



Fig. 6 



a 



Fig. 7 

out again a tube closed at one end (fig. 7) is formed. The 
closed end of the tube may then be rounded by heating it 
strongly and blowing gently into the open end, so as to 
slightly expand the softened portion. Or, if required, a 
bulb may be formed by again heating the closed end and 
blowing into the tube more strongly. 

7. Mounting Platinum Wire.— For a number of 
purposes (paragraphs 26 and 27) a piece of platinum wire, 
about two inches long, and fused into a piece of glass tube 
to act as a holder, will be required. Draw out a piece of glass 



10] 



GLASS MANIPULATION 



5 



tube, as described above, break off the tube at a (fig. 6), 
place one end of the wire in the thin tube so left, and heat 
until the glass fuses round the end of the wire. Allow to 



cr 



Fig. 8 




cool. The glass tube will form a convenient handle for 
holding the wire during heating. Bend the free end of the 
wire into a loop, when it will be ready for use (fig. 8). 

8. Boring Corks. — Corks are readily bored by means 
of sharpened brass tubes. Select a borer slightly less in dia- 
meter than the size of the glass tube to be inserted. Press 
the Gork against a wooden surface and gently rotate the borer 
until a clean hole is 
cut (fig. 9). To make 
the hole smooth a 
round file should be 
used, which will also 
increase the dia- 
meter of the hole. 

9. In boring rub- 
ber corks a very sharp 
borer should be used, and the borer should be moistened 
with glycerine. 

The cork borers can readily be sharpened by a special 
kind of knife sold for the purpose, or they may be filed in 
the interior by a round file, and on the exterior by a tri- 
angular file. 

10. Fitting up Wash-bottle.— Select a thin 18 oz. 
conical flask (fig. 10). Procure a good, sound cork, free 
from flaws or cracks, slightly larger than the inner diameter 
of the neck. Soften the cork by rolling it backwards and 
forwards under the sole of the foot on the floor : this will 
somewhat lessen the diameter of the cork and ensure a 
good fit. 



Fig. 9 



PRACTICAL AGRICULTURAL CHEMISTRY [10-11 



Bore two holes through the cork, as described in para- 
graph 8. Next bend a piece of glass tube at an angle of 
i2o°, as shown in fig. 10 (6), taking care that the ends of the 
tube are rounded (paragraph 5). Force one end just 
through the cork. Now bend another piece of glass tube 
at an angle of 6o° (a) and pass it through the second hole 
in the cork, so as to nearly touch the bottom of the flask. 
If the tubes have been carefully adjusted they will fit 
tightly into the cork, so that when the cork is placed in the 
neck of the flask, and one tube is closed with the finger, no 
<^ air should escape when air is blown 
into the flask from the mouth by 
means of the other tube. 

Upon the end of the larger 
tube (a) a small piece of rubber 
tubing is placed, into which is pushed 
a short piece of glass tube drawn 
out into a jet (c). 

Now fill the flask with distilled 
water. It may either be used for 
propelling a fine jet of water through 
the jet (c) by blowing into the larger 
tube (b), or a larger stream may be 
obtained by inverting the bottle and pouring out of the 
tube (6). If hot water is required the flask may be placed 
on wire gauze on a tripod stand, and the contents of the flask 
heated over the Bunsen flame. 

A rubber cork may be substituted for the wooden one, 
and will be found to last much longer. 

II. Solution. — Most solid substances dissolve in some 
kind of liquid. Water is the most common solvent. The 
amour, t dissolved varies according to circumstances ; hence 
some substances are very soluble, others less so, and some 
only slightly soluble. 

Solution usually takes place most rapidly when the 




Fig. 10 



11--12] 



SOLUTION AND EVAPORATION 



substance is in a fine powder. Heating and shaking also 
promote solution. 

Solution may be of two kinds : (i) simple, when the 
body dissolved does not change in its chemical composition, 
and is therefore left behind on evaporating off the liquid ; 
(2) chemical, when a body of different composition is left 
on evaporating off the liquid. 

a. Simple Solution. — Place a little alum in a 3-in. 
evaporating- dish, nearly fill the dish with water. Heat over 
the Bunsen burner until the solid dissolves. Reserve the 
solution for future use. 




Fig. 11 

b. Chemical Solution.— Place a few pieces of marble in 
a test-tube, add a little dilute hydrochloric acid (HC1). 
The marble, which is insoluble in water, will gradually 
dissolve, carbon dioxide gas being given off (paragraph 39). 

12. Evaporation. — On heating a solution of a sub- 
stance the liquid portion is driven off— evaporated— the solid 
being left behind. 

Experiment— Heat the liquid from paragraph 1 1 b, in 
a small evaporating dish until the liquid is all expelled ; 
white solid calcium chloride 6CaCl 2 ) will be left behind. 



8 PRACTICAL AGRICULTURAL CHEMISTRY [13—15 

Care must be taken that the flame is lessened, as the 
liquid in the dish becomes reduced, or the liquid will spirt, 
i.e. jump out of the dish. 

13. A very convenient form of apparatus is the steam- 
bath shown in fig. 11. It consists of a copper bath, on the 
upper side of which are cut a number of holes to fit various- 
sized evaporating-dishes. The bath is three parts filled 
with water, and heated until the water just boils. The 
dishes containing the liquids to be evaporated can thus 
be kept at a temperature of nearly ioo° C, and loss of the 
liquid by spirting is avoided. The water which is driven off 
from the bath when in use should be replaced from time 
to time, so as to keep the level of the water constant, or better 
a bath may be used which is fitted with an arrangement 
for maintaining the water at a constant level. See fig. 14. 




Fig. 12 

14. Crystallisation. — Take the solution (paragraph 
ii a) and heat over the Bunsen flame until about one-quarter 
of the liquid is left, allow to cool, when crystals of alum 
will form. If the solution is too dilute, and no crystals 
form, further evaporation will be requisite. Most salts are 
more soluble in hot than in cold water; hence the salt 
usually crystallises out on cooling. 

15. Precipitation. — Two clear solutions when added 
together frequently give rise to an insoluble solid, which 
gives a turbid appearance to the mixture. A body so formed 
is termed a precipitate. 

Experiment. — To a little calcium chloride solution in a 
test-tube add a little ammonium carbonate solution ; a 



1G-19] PRECIPITATION AND FILTRATION 9 

white precipitate of calcium carbonate will be formed. 
Reserve the test-tube and contents for use in paragraph 1 7. 

16. Filtration. — Very often it is necessary to separate 
a solid from a liquid in which it is suspended. This 
operation is performed by filtration or decantation (para- 
graph 19). In the former case the liquid and solid are 
thrown upon porous paper, the liquid passes through the 
paper, the solid being retained. Unsized paper, known as 
filter-paper, is used for this purpose. It is usually supplied 
cut into circular pieces. 

17. Fit a filter-paper 
into a funnel (fig. 13) by 
folding it across twice at 
right angles (fig. 12), so as 
to form a conical bag as 
shown at 3. Press this 
bag into the dry funnel, 
and then moisten the paper 
with distilled water. The 
precipitate and liquid from 
paragraph 15 may then be 
poured into the funnel, 
when the liquid passing iaa ^™" FlG n 
through will be quite clear, 
the solid remaining on the filter-paper. 

18. Washing Precipitates.— Precipitates may be 
washed free from adhering solutions either by decantation or 
on the filter-paper, or by a combination of the two processes. 

19. Washing by Decantation.— Prepare a little 
more precipitate, as described in paragraph 15 j allow it to 
stand until the precipitate subsides, then pour off the clear 
supernatant liquid. Add a little distilled water, shake up, 
allow the solid to again subside, and pour off the clear 
liquid. Repeat this operation four or five times, when all 
the soluble matter will be washed out 




IO PRACTICAL AGRICULTURAL CHEMISTRY [20-22 

20. Washing on the Filter-paper. — The precipi- 
tate on the filter-paper (17) can be readily washed by pouring 
into the filter distilled water, allowing it to drain away, and 
repeating the operation four or five times. Hot water is 
best for this purpose, since it filters more rapidly than cold. 
The stream of water from the jet of the wash-bottle should 
be used for this purpose. 




21. In order to ascertain whether a precipitate is 
thoroughly washed, it is necessary either to evaporate a 
few drops of the water which- has passed through the filter, 
or to test for some constituent present in the liquid which is 
to be separated. In the present case, since the liquid will 
be alkaline, the washing should therefore be continued 
until the wash-water ceases to turn turmeric paper brown 
(paragraph 28). 

22. Drying Precipitates. — Precipitates are usually 
dried in a steam-oven (fig. 14), />. a copper oven hollow- 



23-26] IGNITION AND SUBLIMATION II 

cased so as to contain water. The latter on being boiled 
keeps the interior of the oven approximately at a tempera- 
ture of too° C. The arrangement shown at (a) is for 
maintaining the water at a constant level. 

A more rapid way of drying precipitates is to open out 
the filter-paper containing the precipitate on a piece of wire 
gauze, and hold it some distance above the Bunsen flame. 

23. Ignition. — Frequently substances require to be 
heated strongly or ignited. This is best performed in a 
small test-tube called an ignition-tube (6) or on a piece of 
platinum foil 2 in. x 1 in., the latter being held in the 
flame by means of crucible tongs. 

Experiment. — Heat a little solid manganese sulphate in 
an ignition-tube ; the substance will turn black, due to the 
production of the oxide. 

24. Fusion. — On ignition some substances melt or 
fuse; occasionally other substances are added before 
fusion. 

Experiment. — Heat a mixture of sodium carbonate and 
potassium nitrate with a trace of manganese dioxide on 
platinum foil ; a green mass will be produced. 

25. Sublimation. — On heating, some substances go off 
in vapour, but condense again on a cool surface. 

Experiment. — Heat a little ammonium chloride in an 
ignition-tube held in a horizontal position. The salt will 
totally sublime and condense again as a white solid in the 
cold part of the tube. 

26. Flame Colorations. — Certain substances when 
heated in a colourless flame, such as the Bunsen or blow- 
pipe flame, give a distinct coloration to the flame. 

Experiment. — Clean a piece of mounted platinum wire 
(7) by heating it in the blowpipe flame, moistening it with 
hydrochloric acid, reheating, and repeating the operation if 
necessary. Take up a little calcium chloride by means of 
the loop and hold in the flame. A red coloration will be 
given to the flame. 



12 PRACTICAL AGRICULTURAL CHEMISTRY [27-28 

27. Borax Bead. — Fuse a little borax on the loop of a 
platinum wire until it becomes like a bead of colourless 
transparent glass. Now take a very little manganese dioxide, 
and heat in the outer blowpipe flame ; a port-wine tint will 
be imparted to the bead. Next heat in the inner flame ; 
the bead will become colourless. It will thus be seen 
that the two flames may give rise to different coloured 
beads. 

28. Use of Test-papers. — Certain vegetable colours 
are affected by the addition of certain chemicals. The 
test-papers in common use are made by soaking paper in 
litmus or turmeric solutions. They are usually purchased 
in little books. 

Litmus occurs normally as a blue substance. Its 
solution in water or alcohol is at once turned red by acid 
bodies. This reddened litmus is then sensitive to alkalies, 
which give the original blue colour again. 

Turmeric is normally of a yellow colour. Its solution 
is turned brown by alkalies, the yellow colour being 
restored by acids. 

Experiment. — Try the effect of solutions of hydro- 
chloric acid, sodium hydrate, and sodium chloride on 
blue and red litmus and turmeric papers. It will be 
found the first gives an acid, the second an alkaline, and 
the third a neutral reaction. 

Thus by means of test-papers we have a method of 
ascertaining when a reagent is added in excess, provided 
that reagent give a different reaction to the liquid to which 
it is added. 



29-31] 



13 



SECTION II 

THE CONSTITUENTS OF AIR AND WATER 
AIR 

29. Air consists mainly of a mixture of nitrogen and 
oxygen gases : it also contains small quantities of carbon 
dioxide, water-vapour, ammonia and nitric acid. 

Preparation and Properties of Oxygen 

30. Place a few crystals of potassium chlorate in a per- 
fectly dry test-tube and heat in the Bunsen flame. The 




Fig. 15 

substance melts and gives off bubbles of oxygen gas. 
When this takes place, introduce a glowing splinter of wood 
into the mouth of the test-tube. The splinter will burst 
into flame. This behaviour of the glowing splinter is a test 
for the oxygen which is given off from the heated potassium 
chlorate. The following equation represents the chemical 
action that takes place : KC10 3 =KCl + 3 . 

31. In order to investigate the properties of oxygen gas 
a much larger quantity of the gas is required than can be 
prepared by the above method. 



14 PRACTICAL AGRICULTURAL CHEMISTRY [32-33 



Choose a dry test-tube and fit a sound cork into the 
mouth of the tube. Bore the cork, and fit it with a 
bent tube of the shape shown in fig. 15. Next powder in 
a mortar about as much potassium chlorate as will fill a 
small watch-glass, together with about one-fifth as much 
manganese dioxide. One-third fill the test-tube with the 
mixture and place it in a retort-stand, as shown in the 
figure, jtfext place a beehive cell in a larger vessel and add 
water until it reaches about one inch higher than the top of 
the beehive cell. Before commencing to heat the tube, fill 
one of the jars in which the gas is to be collected with 
water, cover its mouth with a ground-glass plate. Invert it 
and place it on the beehive cell, as shown in the figure, 
removing the glass plate when the mouth of 
the jar is under the water See that the end 
of the delivery-tube is directly beneath the 
opening of the jar. Now heat the part of 
the oxygen mixture (potassium chlorate and 
manganese dioxide) nearest the cork with a 
Bunsen flame. Oxygen will come off more 
readily than in the former case (30), and, 
passing through the delivery-tube, will be 
collected in the jar. As soon as one jar is 
filled with the gas, close it with a glass plate 
and remove it from 'the earthenware dish, replacing it by 
another filled with water and inverted in the same manner. 
When three jars have been filled in this way remove 
the delivery-tube from the water and discontinue heating. 

32. One of the properties of oxygen has already been 
shown, i.e. its power of rekindling a glowing splinter of 
wood. All substances which burn in air burn still more 
readily in oxygen. 

33. Burning Sulphur in Oxygen.— Place a small 
piece of sulphur on a deflagrating spoon. Heat it in a 
Bunsen burner until it ignites, then plunge it into a cylinder 




Fig. 16 



34-36] 



PREPARATION OF NITROGEN 



15 



of the gas, as shown in fig. 16. It will burn brilliantly. 
When the sulphur has ceased burning withdraw the de- 
flagrating spoon and pour a little water coloured with a few 
drops of blue litmus solution into the bottle. The sulphur 
dioxide formed by the combination of the sulphur with the 
oxygen will be dissolved, and the litmus will be turned red, 
showing that an acid body has been formed. 

34. Burning Charcoal in Oxygen.— Place a piece 
of charcoal in a clean spoon and burn it in a jar of oxygen, 
just as the sulphur was burned in the last experiment. It 
will glow brightly but will give no flame. After all burning 
has ceased pour lime-water into the jar and shake up. The 
lime-water will turn milky owing to the presence of carbon 
dioxide, which is formed when charcoal is burned in 
oxygen. The action of carbon dioxide on lime-water is 
the more fully explained in paragraph 42. 

Preparation and Properties of Nitrogen 

35. The most convenient source of nitrogen is the air, 
which consists chiefly of a mixture of the two gases oxygen 
and nitrogen in the proportion of four volumes of the latter to 
one of the former. To prepare nitrogen 
it is only necessary, then, to remove 
the oxygen from a portion of the air. 

36. Experiment. — Half fill a stone- 
ware dish with water and float on its 
surface a small evaporating dish. In 
the dish place a piece of phosphorus 
about the size of a pea. Care must 
be taken not to ignite the phosphorus. 
It should be cut under water and dried ^Jg 
as rapidly as possible by means of 
filter-paper. Next place a stoppered 
bell-jar over the basin, as shown in figure 17. Ignite the 
phosphorus by touching it with a hot wire. Quickly withdraw 




16 PRACTICAL AGRICULTURAL CHEMISTRY [37-40 

the wire and stopper the bell-jar. The interior will first fill 
with white fumes, then the phosphorus will go out, and finally 
the white fumes will disappear, leaving the interior clear 
again. As the fumes disappear the water will rise in the 
bell-jar, showing that the volume of gas inside has con- 
tracted. 

37. The explanation of this is as follows : As the 
phosphorus burns it combines with the oxygen of the air to 
form phosphorus pentoxide, which is a white solid body, 
and hence appears as a white cloud. When all the oxygen 
has been used up the phosphorus goes out. Next the 
phosphorus pentoxide dissolves in the water, and so 
practically nothing is left in the bell-jar except the nitrogen, 
which occupies only four-fifths of the total volume of the 
oxygen and nitrogen originally present. 

38. Experiment. — Nitrogen neither burns nor does it 
support combustion. To test this add water until the level 
is the same outside as it is inside the bell-jar, open the 
stepper and plunge the lighted taper into the gas ; the taper 
will at once be extinguished. 

Preparation and Properties of Carbon Dioxide 

39. Fit a Woulffe's bottle with thistle-funnel and 
delivery tube as in fig. 18. Place in the bottle a few 
pieces of marble. Pour down the thistle-funnel enough 
water to cover the marble, then add a little strong hydrochloric 
acid. A brisk effervescence will take place, and carbon 
dioxide will be evolved. 

40. Place a cylinder under the end of the delivery 
tube. Since the gas is so much heavier than air it will 
fall to the bottom. After the apparatus has been work- 
ing for about half a minute hold a lighted taper just over 
the mouth of the jar. When the jar is full the gas will come 
in contact with the taper and extinguish it. 



41-42] CARBON DIOXIDE AND AMMONIA 



17 



41. Carbon dioxide gas resembles nitrogen in that it 
will extinguish a flame as shown in the last experiment, but 
it differs from it in several ways. To show that it is much 
heavier than air pour the gas from one jar into another, 
as shown in figure 19. As the gas is invisible, nothing will 
be seen to pass. Now plunge a lighted taper into each of 
the jars. In the one which originally contained the gas, 
the taper will continue burning, showing that no carbon 
dioxide remains, whilst in the other jar the taper will be 
extinguished, showing that the heavy gas has been poured 
from the first jar into the second. 

42. Another property by which carbon dioxide may be 
recognised is its action on lime-water. Half fill a small 

beaker with lime-water 
and place it so that the 
delivery-tube of the ap- 
paratus (fig. 18) dips into 
the liquid. Allow the gas 
to pass through the lime- 
water for a few minutes. 




I 



Fig. 18 



Fig. 19 



First the liquid becomes milky, because the lime has 
combined with the carbon dioxide to form carbonate of 
lime or chalk, which is not soluble in water. In a short 
time, however, the liquid becomes clear again : this is 
because the chalk, although insoluble in pure water, is 
soluble in water which contains carbon dioxide gas dissolved 
in it. If the clear liquid is boiled for a few minutes the 

c 



1 8 PRACTICAL AGRICULTURAL CHEMISTRY [43-44 

chalk will deposit as a white incrustation on the sides and 
bottom of the beaker. Carbonate of lime exists in this 
form in natural waters, and is called ' temporary hard- 
ness ' (60 d). 



T — if 



Preparation and Properties of Ammonia 

43. Ammonia is generally prepared by heating together 
slaked lime and ammonium chloride. Grind together in a- 
mortar equal parts of ammonium chloride and slaked lime, 
place a little of the mixture in a test-tube and heat it. 
Notice the strong smell of the ammonia which is formed. 

44. To obtain larger quantities of the gas it is much 
more convenient to prepare it from its solution in water. 
If strong ammonia solution is warmed the gas comes off 

in a rapid stream. 

Set up the apparatus 
shown in fig. 20, placing 
a small quantity of the 
strongest ammonia solu- 
tion in the flask. Since 
ammonia is lighter than 
air it may be collected 
by upward displacement. 
To do this place a jar 
over the evolution-tube 
and warm the flask cau- 
tiously. The gas will 
ascend into the jar. Now 
dip a glass rod into 
FlG - 20 strong hydrochloric acid 

and hold it near the mouth of the jar. When the jar is full 
the ammonia gas coming in contact with the hydrochloric 
acid will form dense white fumes around the moist part of 
the rod. Discontinue heating and remove the jar. 




45-49] EXPERIMENTS ON AIR 19 

45. One of the most striking properties of ammonia gas 
is its extreme solubility in water. Place a ground-glass plate 
over the mouth of a jar filled with the gas as in the last 
experiment. Then hold the jar so that its mouth dips under 
the surface of the water contained in an earthenware dish. 
Remove the glass plate. The water will rush up into the jar. 

46. Another property of ammonia is its action on tur- 
meric paper, which it turns brown. Take a few drops of 
strong ammonia in a test-tube. Moisten a strip of turmeric 
paper and hold it over the mouth of the test-tube. It will 
probably become brown at once from the ammonia which 
escapes from the solution. If it does not alter its colour 
warm the liquid slightly ; the paper will immediately be- 
come dark brown. 

EXPERIMENTS ON AIR 

47. Of the minor constituents of the atmosphere (29) 
carbon dioxide and water-vapour may be readily detected, 
but the presence of nitric acid and ammonia are less readily 
shown. Methods for detecting carbon dioxide and water - 
vapour in air are described below. 

48. Carbon Dioxide in Air.— Pour a little clear 
lime-water into a saucer or shallow evaporating-basin and 
allow it to stand for an hour. At the end of that time it 
will be covered by a thin film of carbonate of lime or chalk. 
This is produced by the action of carbon dioxide, as ex- 
plained in paragraph 42, and shows the presence of that 
gas in the air. 

49. Water-vapour in Air.— Place on a dry porce- 
lain tile a few lumps of dry calcium chloride and allow 
them to stand for an hour. At the end of that time the 
lumps will have become quite wet. The moisture which 
has been thus attracted can only have come from the air. 
This experiment, therefore, shows that the air contains 

water-vapour. 

c 2 



20 PRACTICAL AGRICULTURAL CHEMISTRY [50-51 



WATER 

50. Water differs chemically from air in being a compound 
of the two gases oxygen and hydrogen, whereas air was seen 
to be a mixture of the gases nitrogen and oxygen. 

The properties of oxygen have been already described 
(30-34). The preparation and properties of hydrogen are 
described below. 

Preparation and Properties of Hydrogen 

51. Fit up the apparatus for this experiment as shown in 
fig. 21. Place a handful of granulated zinc at the bottom of 




Fig. 21 

the Woulffe's bottle and pour sufficient water down the thistle- 
funnel to cover the zinc. Now add some strong hydro- 
chloric acid, when a brisk effervescence will ensue. Do not 
collect the first portion of gas, but after it has been in action 
for two or three minutes fill a test-tube with water, invert it 
in the water, and allow the gas to pass into it. When it is 
full of gas close it with your thumb and bring it close to a 
lighted burner. Remove your thumb and apply the light to 
the tube. If the gas be pure it will burn steadily ; if it con- 
tain air it will explode with a sharp squeak. Continue 



52-55] PROPERTIES OF HYDROGEN 21 

testing until it is quite free from air, then collect a few 
cylinders as described in paragraph 31. 

52. Hydrogen burns but does not support combustion. 
As soon as a cylinder is full of hydrogen remove it from 
the trough, keeping its open end downwards, and thrust a 
lighted taper into it. The taper will be extinguished, but 
the hydrogen itself will burn with a flame which is scarcely 
visible. 

53. Hydrogen is the lightest substance known. Fill 
another cylinder with hydrogen and pour the gas upwards 
into a cylinder which contains nothing but air. Then test 
each cylinder with a lighted taper. The one which formerly 
contained the gas will have no effect on the taper, whilst 
the one which formerly contained no hydrogen will give a 
sharp explosion, showing that hydrogen is lighter than 
air. 

54. Fill a short thick cylinder with water, then invert it 
in a dish of water. Displace about two-thirds of the water 
with hydrogen and the rest with oxygen. Allow the gases 
to stand for a few minutes to mix thoroughly, then apply a 
lighted taper ; a loud explosion will take place, due to the 
gases combining to form water. 

55. The energy of the combination of the gases in the 
last experiment prevents the water formed from being readily 
collected. But if hydrogen is allowed to combine with the 
oxygen of the air under suitable conditions the water may 
be collected. Replace the bent delivery-tube (fig. 21) by 
a straight piece of glass tube 6 inches long. Allow an 
energetic stream of hydrogen to pass for some minutes, 
then ascertain that the hydrogen is free from air by the 
following test. Hold a small test-tube over the end of the 
upright tube for half a minute, close the mouth of the tube 
with the thumb and apply a light. If the gas is free from 
air it will burn quietly up the tube j if it explodes with a 
squeaking noise continue the evolution of the gas until the 



22 PRACTICAL AGRICULTURAL CHEMISTRY [-56-57 

tube of gas burns quietly. To prevent accidents it is better 
to cover the Woulffe's bottle with a glass-cloth. 

When the hydrogen is free from air ignite the stream of 
gas and hold over the flame a clean, dry beaker. After a 
time drops of water will collect inside the beaker, which 
will be found to have the ordinary properties of pure water. 

EXPERIMENTS ON WATER 

56. Natural Waters. — Dissolved substances are 
always present in the water which occurs in nature. Even 
carefully collected rain-water contains some impurities dis- 
solved out of the air. Spring, river, and well waters con- 
tain also dissolved matters, obtained from the soil or rock 
with which they have been in contact. 

57. Distillation of Water.— The water obtained 
from the general supply of a town is seldom sufficiently 



Fig. 22 

pure for use in a laboratory, as it contains several substances 
in solution. It may be freed from these impurities by the 
process known as distillation. The apparatus required for 
this operation is shown in fig. 22, and consists of a retort 
whose neck leads into a flask which is kept as cool as 
possible by being immersed in a vessel of water. Half fill 
the retort with water and heat it with a Bunsen flame, prefer- 



58-00] EXPERIMENTS ON WATER 23 

ably with the flame from a rose burner. The water will boil, 
and the steam will pass over until it comes into the cool flask, 
where it will condense. In this manner pure water will be 
collected in the flask, whilst the impurities are left behind 
in the retort. 

58. For the tests described in the next seven experiments 
three kinds of water should be used, i.e. distilled water, 
ordinary water as supplied to the laboratory, and some 
sample of really impure water, such as drainage water. 

59. Solid Matter in Water.— Half fill three evapo- 
rating-basins with the different waters under consideration 
and evaporate each to dryness. Notice the residue, if any, 
left in each case. When the residue is quite dry hold the 
dish in a Bunsen flame for a minute or so. Should there 
be any organic impurities in the water, such as are derived 
from decomposing animal or vegetable matter, the residue 
in the dish will become discoloured and blackened. The 
distilled water will be found to leave no residue. The 
laboratory water will leave a residue which will probably 
remain white on further heating. The drainage water will 
leave a residue which blackens on heating. 

60. Various Dissolved Salts in different Classes 
of Water. — The common dissolved impurities are the sul- 
phates and carbonates of lime and magnesia, and in smaller 
amounts common salt and ammonia. A few experiments 
are described below to show the method of testing for these 
impurities, and of roughly comparing the amounts present. 

a. Lime in Water. — Half fill three clean test-tubes 
with the three samples of water. Place them side by side 
in the test-tube rack and add to each a few drops of am- 
monia and a little ammonium oxalate solution ; allow to 
stand a few minutes. The distilled water will suffer no 
change, whilst the other two will become cloudy. Notice 
which gives the thickest cloud, as that one will contain 
most lime, and will probably be the hardest water. 



24 PRACTICAL AGRICULTURAL CHEMISTRY [60 

b. Sulphates in Water.— It is very seldom that a 
natural water contains sulphuric acid in the free state, but 
most spring waters contain it in combination with lime or 
magnesia. Add to portions of the different kinds of water 
in three test-tubes a drop of hydrochloric acid and ten drops 
of barium chloride. A cloudiness, which may require a few 
minutes to form, shows presence of sulphuric acid. The dis- 
tilled water contains no sulphate, whilst the other two con- 
tain it in varying quantities, as shown by the milkiness. 

c. Carbonates in Water.— Half fill three small 
beakers with specimens of the different waters and boil 
each for twenty minutes. Pour out the water and notice the 
deposit (if any) in each case. The deposit is due to car- 
bonate of lime, which deposits when the carbon dioxide is 
driven out of the water (42). If a few drops of a dilute 
hydrochloric acid are added, the precipitated carbonate will 
effervesce (195). 

d. Salt in Water.— Half fill three test-tubes with the 
samples of waters as directed in the last experiment and 
add a drop of dilute nitric acid and ten drops of silver nitrate 
to each. The distilled water will not change in appearance. 
That water which gives most cloudiness contains most 
salt. 

e. Hardness of Water.— The presence of dissolved 
salts of lime and magnesia in water causes the precipitation 
of soap. Water which produces this result is termed ' hard/ 
Salt (sodium chloride) if present in large amount will also 
produce this result. 

Dissolve a shaving of soap in a little distilled water and 
shake up a little of the solution with the three samples of 
water previously placed in test-tubes. The distilled water 
will immediately produce a lather and remain clear, whereas 
the other samples will become turbid and produce no 
lather until a larger quantity of soap solution is added. 
The amount of soap solution necessary to form a lather is 



60] EXPERIMENTS ON WATER 2$ 

a rough indication of the * hardness ' or soap-destroying 
power of the water. 

f. Ammonia in Water. — Take three test-tubes half 
filled with the different kinds of water as before, and to each 
add ten drops of Nessler's Solution. This is one of the most 
delicate tests known to chemists, and should the smallest 
trace of ammonia be present, the water to which the Ness- 
ler's Solution (265) has been added will become coloured 
yellow or brown, according to the amount of ammonia 
present. So delicate is the test that distilled water, unless 
it has been specially prepared, will contain sufficient ammo- 
nia to show it. After the test-tubes have stood two or three 
minutes notice their colour by holding them over a sheet 
of white paper and looking down through the length of the 
tube. The drainage water will be much more coloured 
than the other two. As the most probable source of am- 
monia in a natural water is decaying animal matter it will 
be seen that it is very necessary that drinking water shall 
contain as little of this substance as possible. 



26 PRACTICAL AGRICULTURAL CHEMISTRY [61-63 



SECTION III 

EXPERIMENTS ON SOILS, MANURES, FEEDING 
MATERIALS, AND DAIRY PRODUCE 

EXPERIMENTS ON SOILS 

61. Arable soils consist principally of four substances- 
sand, clay, limestone, and humus or organic matter — 
and the varieties of soil are named according to the pro- 
portions in which the above constituents are present. Thus, 
certain soils are known as sandy soils, clay soils, limestone 
soils, and peat soils. Besides these are loams, which 
contain both sand and clay in large quantities; marls, 
which consist principally of limestone and clay ; and cal- 
careous soils, in which sand and limestone occur together. 

62. Separation of Sand and Clay. — Place ina3-ia 
evaporating-basin about as much dried loam as will cover a 
penny. Half fill the basin with distilled water, and boil it for a 
few minutes. Stir up and pour out the whole of the contents 
into a small beaker. Allow the beaker to stand for a few 
minutes, then pour off the cloudy liquid into another beaker, 
leaving the sediment behind. Now hold the beaker contain- 
ing the sediment over a sink and allow water to run into it 
for a few minutes. The fine particles of clay will be washed 
away, and very soon the water will run off quite clear The 
residue in the beaker is sand. 

63. Action of Lime on Clay. — Frequently imie is 
added to a clay soil to make it more open and sandlike in 
its properties. To illustrate this action pour into two test- 
tubes a little of the clay-water prepared in the last experiment. 
To one of these add a thimbleful of lime-water and allow 



64-66] EXPERIMENTS ON SOILS 2J 

them to stand for an hour or so. The clay will scarcely 
have settled at all in the one to which no lime-water has 
been added, whilst the other will have become almost clear 
owing to the clay having fallen to the bottom of the liquid 
as though it were fine sand. 

64. Limestone in Soil. — In paragraph 39 it was shown 
that when hydrochloric acid is added to marble (which is a 
form of limestone) effervescence takes place, and carbonic 
acid gas is evolved. Take a small quantity of soil in a 
test-tube and moisten it with water. Fill the test-tube 
about half full of dilute hydrochloric acid. If the soil 
contains considerable quantities of limestone the effer- 
vescence will be seen at once. Should only traces be 
present the effervescence may be detected by holding the 
mouth of the test-tube close to the ear, when the sound 
caused by the gas coming off will be distinctly heard. 

65. Test for Lime. — Lime is oxide of calcium ; for a 
full set of tests for that metal see paragraphs 1 78-1 81. 
It usually exists in soils combined with carbonic acid. 
To test for lime in a soil : boil the mixture of boil and 
acid described in paragraph 64 for a minute, then add 
ammonia to it until it is alkaline, and filter. To the clear 
liquid so obtained add a little ammonium oxalate and allow 
the liquid to stand for a few minutes. A white precipitate or 
cloudiness shows that the soil contained lime. 

66. Test for Organic Matter (Humus).— Place a 
little soil on a piece of platinum foil and hold it with a pair 
of crucible tongs just over the top of a Bunsen flame. The 
soil will first of all darken in colour until nearly black, then 
it will become lighter again until it is of much the same colour 
as it was before heating. The reason of these changes is that 
the organic matter (which always contains carbon) becomes 
charred, and the carbon so formed gives a dark colour to 
the substance. After a while the carbon itself burns, and 
leaves the soil as it was before the experiment, except that 
the organic matter has been burned away. 



28 PRACTICAL AGRICULTURAL CHEMISTRY [67-69 

* 67. The Nature of Humus. — The organic matter 
or humus in a soil consists principally of certain acids, 
which, like all other acids, combine with caustic potash to 
form salts. The soil acids themselves are not soluble in 
water, but the compounds which they form with caustic potash 
are soluble. To show this, place a small quantity of peat soil 
at the bottom of a test-tube and fill the tube about one-third 
full of caustic potash solution. Warm for a few minutes, 
then fill up the test-tube with water, shake well, and 
filter. The liquid which comes through will be coloured 
brown by the potash compounds in solution. Take a 
little of the solution in a test-tube and add an excess 
of dilute hydrochloric acid. The liquid will become cloudy 
because the soil acids will be again set free from the 
potash, and, as they are not soluble in water, they will form 
a precipitate. 

EXPERIMENTS ON MANURES 

68. The most important constituents of manures arc 
lime (CaO), potash (K 2 0), phosphoric acid (P 2 5 ), and 
nitrogen (N). Most natural manures, such as farmyard 
manure and guano, contain all these substances. Artificial 
manures are generally made by mixing substances which 
contain one or more of the above constituents in a concen- 
trated form. The experiments described in paragraphs 69, 
70 are to show the properties of the various simple manures 
before mixing. 

Lime Manures 

69. Slaking Lime.— Place a lump of freshly prepared 
lime, about the size of a small nut, on a tile and pour a few 
drops of water on to it. When this water is soaked up, pour 
a few more drops, and continue this process as long as the 
lime will continue to absorb it and still remain dry. The 
lime will shortly become hot and fall into a fine powder, 



70-72] LIME MANURES 2Q 

showing that chemical action has taken place, and the quick- 
lime has combined with the water to form slaked lime. 

70. Solubility of Lime. — Although limestone (car- 
bonate of lime) is not soluble in pure water, slaked lime 
(hydrate of lime) is. Place a little powdered marble in a 
test-tube, and in another place a little of the slaked lime 
obtained in the last experiment. Add to each half a test- 
tube full of water and shake up. Allow both to settle and 
pour off the clear liquid into two other test-tubes. Filter 
if necessary. To each of these two clear liquids add a few 
drops of ammonium oxalate. The one in which the marble 
has been shaken will remain clear, showing that none has 
been dissolved ; whilst the other will give a white precipitate, 
showing that some of the slaked lime has entered into 
solution. 1 

71. Action of Air on Lime. — When lime is ex- 
posed to the air it absorbs carbonic acid and is converted 
into carbonate of lime, which is known as mild lime. Pour 
a little lime-water (a solution of slaked lime in water) into 
an evaporating-dish and leave it exposed to the ah' for an 
hour or two. At the end of that time it will be covered 
with a thin scum. This is because the lime in the solution 
has been turned into carbonate of lime, which, being 
insoluble in the water, forms a scum over the surface. 

72. Action of Lime on Acids.— Lime is not only 
useful as a food for plants, but it improves the soil in many 
other ways. One of these has already been pointed out in 
paragraph 63. Another use of lime is to add it to * sour ' 
soils, or soils which contain such quantities of acid that they 
will not grow good crops. To show this action, one-third fill 

1 Distilled water is seldom perfectly free from carbon dioxide ; 
hence a trace of the marble is often dissolved, giving a faint precipitate 
with ammonium oxalate. When this is the case the student should 
notice the great difference between the precipitate obtained after using 
lime and that obtained by using marble. 



30 FRACTICAL AGRICULTURAL CHEMISTRY [73-75 

a test-tube with distilled water, then add a few drops of 
hydrochloric acid and a few drops of litmus solution. The 
acid will colour the litmus red. Now add a few drops of 
lime-water and shake up. If the liquid be still red (i.e. if 
it be still acid) add a few more drops of lime-water and 
shake up again. Continue doing so until the colour 
changes to blue. When this takes place all the acid will 
have been neutralised. 

* 73. Action of Lime on Salts of Iron.— Soluble salts 
of iron are often injurious to crops. Lime has the property 
of rendering these salts insoluble. Dissolve a crystal of 
ferrous sulphate (copperas) in half a test-tube of cold water. 
Add a little lime-water. The iron in the solution will be 
rendered insoluble and a dark-coloured precipitate of fer- 
rous hydrate will be formed. 

74. Sulphur in Gas-lime.— Lime which has been 
used in the purification of coal-gas, called gas-lime, is some- 
times used as a manure and insecticide, but unless it is 
exposed to the action of the air for a considerable time it 
acts as a plant poison, as it contains calcic sulphide. To 
show the presence of a sulphide, place a little gas-lime in a 
test-tube and add a little dilute hydrochloric acid. Effer- 
vescence takes place and the calcic sulphide is decomposed, 
forming sulphuretted hydrogen, which may be recognised 
by its offensive smell. 

* 75. Sulphur in Gypsum.— Gypsum (sulphate of lime) 
contains sulphur, but as a plant-food. Treat a little gypsum 
as in the last experiment. No sulphuretted hydrogen will 
be given off. Mix a little gypsum in a mortar with twice its 
weight of powdered charcoal. Place a little of this mixture 
on a piece of platinum-foil and heat over a Bunsen flame 
until all the charcoal is burned off. Allow to cool, then place 
the mass in a test-tube and add a little dilute hydrochloric 
acid. Sulphuretted hydrogen will now be evolved, showing 
that sulphur was present in the gypsum. The action of the 



76-78] PHOSPHATIC MANURES 3 1 

air on gas-lime is to turn the calcic sulphide (CaS) to gypsum 
(CaS0 4 ). The heating with charcoal brings about the 
opposite effect, i.e. reduces the gypsum to calcic sulphide. 

Potash Manure 

76. Potash in Kainit— Kainit is the most common 
potash manure. To show that it contains potassium, place 
a little kainit on a watch-glass and moisten it with dilute 
hydrochloric acid. Test this substance in the flame as 
directed on page n. The flame will appear yellow, due to 
sodium present as an impurity. Now observe the flame 
through an indigo prism or a piece of cobalt-blue glass. It 
will appear crimson. This is a distinctive test for potash 

(189). 

Phosphatic Manures 

77. Phosphoric Acid. — This generally occurs in 
artificial manures as a phosphate of lime. These phosphates 
are four in number, and each has its own distinctive 
properties. Their chemical names and formulae are as 
follows : — 

a. Monocalcic phosphate . CaO.(H 2 0) 2 .P 2 5 

b. Bicalcic phosphate . (CaO) 2 .H 2 O.P 2 5 

c. Tricalcic phosphate » (CaO) 3 .P 2 5 

d. Tetracalcic phosphate (CaO) 4 .P 2 5 

Their commercial names are — 

a. Superphosphate of lime. b. Reverted phosphate. 

c. Bone or mineral phosphate, d. Slag phosphate. 

The properties of slag phosphate are very similar to 
those of reverted phosphate, so in the next three experi- 
ments reverted phosphate is not considered, but it is referred 
to in paragraph 81. 

78. Action of Water on Phosphates.— Into three 



32 PRACTICAL AGRICULTURAL CHEMISTRY [79-81 

test-tubes introduce equal quantities respectively of coprolite 
powder (which contains bone phosphate), basic slag (which 
contains slag phosphate), and superphosphate. About as 
much as can be held on a sixpence will be sufficient. Half 
fill each test-tube with distilled water and shake up. Filter 
each one into a clean test-tube through separate filters. If 
the solutions do not come through clear, pass them through 
the filters again. Now test each solution for phosphoric 
acid. This is done by adding an excess of ammonium 
molybdate solution and boiling ; a yellow precipitate 
shows that phosphoric acid is present. It will be found 
that the liquid from the superphosphate contains phos- 
phoric acid, but that the others do not, showing that 
superphosphate of lime is the only one of the three 
substances that is soluble in water. 

* 70. Action of Ammonium Citrate on Phos- 
phates. — Place small quantities of superphosphate, slag 
and coprolite powder in separate test-tubes, as in paragraph 
78. Shake up with ammonium citrate solution. Filter 
and test with ammonium molybdate as before. This time 
the liquids from both the slag and the superphosphate will 
be found to contain phosphoric acid, whilst that from the 
bone phosphate will not, showing that both superphosphate 
and slag phosphate are soluble in ammonium citrate, whilst 
bone phosphate is not. 

80. Action of Dilute Nitric Acid on Phosphates. 
Proceed exactly as in the two previous experiments, 
treating the different phosphates with dilute nitric acid. 
Filter and test as before. All three phosphates will be 
found to be soluble in nitric acid, and will therefore give 
the molybdate test. 

81. Reversion of Superphosphate.— When a super- 
phosphate is placed on the soil the rain dissolves the soluble 
substance and thoroughly impregnates the soil with it. If 
it were to remain soluble, a quantity would eventually be 



82-84] NITROGENOUS MANURES 33 

washed away into the drains. This, however, does not 
occur, as several substances in the soil cause it to ' revert,' 
or turn into reverted phosphate, which, like slag phosphate, 
is insoluble in water. The principal substances which 
bring about this reversion are lime, oxide of iron, and 
alumina. This reversion is shown in the next experiment. 

82. Action of Lime on Superphosphate. — Mix a 
little superphosphate in a mortar with twice its weight of 
freshly slaked lime. Grind them well together and intro- 
duce a small quantity into a test-tube. Add distilled water 
and shake well, then allow to settle. When the liquid has 
become n2arly clear, filter and test the clear liquid with 
ammonium molybdate. No phosphoric acid will be found. 
The lime has reverted the superphosphate and rendered it 
insoluble. 

* 83. Action of Ammonium Citrate on Reverted 
Phosphate. — Take a little more of the mixture of lime 
and superphosphate made in the last experiment in a test- 
tube and treat it with ammonium citrate solution. Filter, 
and test with ammonium molybdate. The reverted phos- 
phate will be found to resemble slag phosphate in that it 
dissolves in ammonium citrate. 

The vegetable acids in soil act very much in the same 
way as ammonium citrate, so that the reverted phosphate, 
which has been formed and thoroughly mixed with the soil 
by the action of rain, lime, &c, on superphosphate, is slowly 
redissolved and given up to the plants as food. 

Nitrogenous Manures 

84. The nitrogen in manures occurs in one or more of 
three forms known chemically as organic nitrogen, ammo- 
niacal nitrogen, and nitric nitrogen. In whatever form it 
may occur, the action of the organisms in the soil is to turn 
it into the last of the three, as this is the only form in which 

D 



34 PRACTICAL AGRICULTURAL CHEMISTRY [85-87 

it is fit for plant-food. The following three experiments 
show how the different forms may be recognised. 

85. Test for Organic Nitrogen.— Mix together in a 
mortar about as much shoddy (which has been cut up very 
finely with a pair of scissors) as can be heaped up on a shil- 
ling with about four times its weight of soda lime. Heat a 
little of this mixture strongly in an ignition-tube (6). Am- 
monia gas will be given off, which may be recognised by its 
smell, and also by the fact that it turns moist turmeric 
paper brown. 

Treat a little sulphate of ammonia in exactly the same 
way as the shoddy. Ammonia will be given off more 
readily than in the former case. 

Treat a little nitrate of soda in the same way. No am- 
monia will be given off. 

Shoddy contains organic nitrogen, sulphate of ammonia 
contains ammoniacal nitrogen, and nitrate of soda contains 
nitric nitrogen. From the experiment just performed it will 
be seen that the organic and ammoniacal forms are similar 
in that they both give off ammonia when heated with soda 
lime. They are distinguished from each other by the 
experiment described in paragraph 86. 

86. Test for Ammoniacal Nitrogen.— Take three 
test-tubes : in the first, place a little shoddy, cut up fine ; 
in the second, a little sulphate of ammonia ; and in the 
third, a little nitrate of soda. Half fill each test-tube with 
potassic hydrate solution, and boil each in turn. The one 
containing sulphate of ammonia will give off ammonia, which 
may be recognised as before, whilst the other two will 
not Ammoniacal nitrogen may always be recognised in 
this way. 

87. Test for Nitric Nitrogen. — Take separate small 
portions of sulphate of ammonia, shoddy, and nitrate of 
soda in test-tubes and add water. Filter each and to the 
clear liquid add a few drops of indigo solution ; then pour 



88-90] THE MIXING OF MANURES 35 

in strong sulphuric acid until the volume of liquid is 
about doubled. In the case of shoddy and sulphate of 
ammonia no change will take place. With nitrate of soda 
the indigo will be bleached. This operation may be used 
as a test for nitrates in manures. 

The Mixing of Manures 

88. In mixing manures care must be taken not to mix 
two substances which act chemically upon each other. 
Attention has already been called to the fact that lime acts 
upon superphosphate (82), rendering the phosphoric acid 
insoluble in water ; and since basic slag contains a certain 
quantity of lime it should not be mixed with super- 
phosphate. Other substances which should not be mixed 
are shown in paragraphs 89 and 90. 

89. Action of Superphosphate on Nitrate of 
Soda. — Mix equal quantities of superphosphate and 
nitrate of soda in a mortar. Notice the peculiar smell of 
the mixture. Heat a small quantity in an ignition- tube. 
It will give off brown fumes. The reason is that super- 
phosphate contains a certain amount of free sulphuric acid 
which is used in its manufacture, and tlus acts upon the 
nitrate of soda, setting free nitric acid, which is recognised 
by its smell and the brown fumes formed when it is heated. 
Now since nitric acid contains nitrogen, and is volatile, it 
will pass off into the air, and so nitrogen will be lost. 
Further, nitric acid is a very corrosive substance, and will 
attack the bags in which manure is stored. Hence super- 
phosphate and nitrate should never be mixed before ap- 
plying them to the land. 

90. Action of Slag on Sulphate of Ammonia.— 
Mix a small quantity of sulphate of ammonia with about 
six times its bulk of basic slag in a mortar. Notice the 
smell of ammonia. Heat a little of the mixture in an 
ignition-tube, and hold a piece of moist turmeric-paper over 

d2 



36 PRACTICAL AGRICULTURAL CHEMISTRY [91-94 

the end of the tube. The paper will become brown. This 
experiment teaches that when these two substances are 
mixed ammonia passes off into the air and is lost ; and 
since ammonia contains nitrogen this loss is a serious one. 



TESTING MANURES 

91. To find the exact value of a manure it is necessary, 
to make a full quantitative analysis. There are, however, 
a few simple tests by which the purity of a manure or the 
composition of a mixed manure may be recognised. These 
are detailed in paragraphs 92-106. 

92. Ammonia in Guano.— No single test can be 
applied which will guarantee the purity of a Peruvian guano, 
but the one described in this paragraph, together with those 
in the next two experiments, will give a fair idea of its 
genuineness. Take a little guano in a test-tube, and treat it 
with potash exactly as was described in the case of nitrogen- 
ous manures (86). A genuine guano contains ammoniacal 
nitrogen, and hence ammonia will be evolved, which will 
turn turmeric-paper brown. 

93. The Ash of Guano.— Place a little guano on 
a piece of platinum foil, and hold it by means of a pair of 
crucible tongs in the flame of a Bunsen burner. The 
guano will first darken in colour, then catch fire and flare 
up. When it ceases burning a black mass of charcoal will 
be left. Continue heating until all the charcoal is burned 
off. The mass now left on the foil is known as the ash of 
the guano, and should be quite white. If it is brown the 
guano has been adulterated. 

94. Soluble Phosphoric Acid in Guano. — Treat 
a small quantity of guano with water in a test-tube as 
described in paragraph 78. Filter and heat the liquid with 
excess of ammonium molybdate solution. A yellow pre- 
cipitate will be formed, showing that the guano contained 



95-98] TESTING MANURES 37 

phosphoric acid in a soluble state. The guano may be 
distinguished from superphosphate by moistening a small 
quantity on a tile and laying a piece of blue litmus over it. 
The litmus will not change. If this be tried with super- 
phosphate the litmus-paper will be reddened. 

95. Volatility of Sulphate of Ammonia. — Place 
a few crystals of pure sulphate of ammonia on a piece of 
platinum foil, and heat over a Bunsen flame. The crystals 
will first of all melt, then white fumes will rise from the 
substance, and finally it will vanish entirely, leaving no 
trace whatever on the foil. - Repeat the experiment with a 
few crystals of commercial sulphate of ammonia. Exactly 
the same series of changes will take place, except that a 
slight film of impurity will be left on the foil. The smaller 
this film, the purer the sulphate will be. 

06. Thiocyanates in Sulphate of Ammonia.— 
Occasionally sulphate of ammonia contains a powerful plant 
poison, known as thiocyanate of ammonia, which should 
always be tested for. Add to a solution of ammonium 
thiocyanate a few drops of ferric chloride solution ; a blood- 
red liquid will be formed. Now make a solution of com- 
mercial sulphate of ammonia in water and treat in the same 
way by adding a drop of ferric chloride. Should the least 
red coloration occur, the sulphate is unfit for use. 

97. Action of Heat on Bones.— Samples of bones 
can usually be recognised by their appearance, except when 
in the state of bone-flour. Bone-flour may be recognised 
by the following test. Heat a little of the substance on 
platinum foil as in paragraph 93. The bones will give off 
an offensive smell, which is easily recognisable. The sub- 
stance will next blacken from the formation of carbon, 
and finally become quite white again, owing to the organic 
matter being burnt away and only ash left. 

98. Action of Acid on Bones.— Place a small 
quantity of bone-flour at the bottom of a test-tube and add 



38 PRACTICAL AGRICULTURAL CHEMISTRY [99-101 

a small quantity of dilute hydrochloric acid. The liquid 
will effervesce, owing to the fact that bones contain carbonate 
of lime. 

COMPOUND MANURES' 

* 99. The following set of experiments (paragraphs 100- 
106) should be performed on several mixed manures. The 
object of the experiments is to find out what are the principal 
constituents of the manures. 

* 100. Test for Acidity.— Place a little of the mixed 
manure on a watch-glass, moisten it thoroughly with water, 
and lay a piece of moist blue litmus-paper upon it. Should 
the litmus-paper immediately become red, the manure con- 
tains some acid, and most probably contains superphosphate 
of lime. 

* 101. Test for Soluble Phosphate.— Place about 
as much of the manure as could be held on a penny in a 
mortar, cover with cold distilled water, and grind into a paste 
with the pestle. Allow the liquid to settle for two or three 
minutes, then filter it, washing the mud into the filter-paper 
with hot water. Save the residue for the next experiment 
Divide the filtrate into two portions in test-tubes. Test one 
portion for phosphoric acid by boiling with excess of ammo- 
nium molybdate solution. 

Should a yellow precipitate occur, then the manure con- 
tains soluble phosphoric acid, and should the manure have 
been proved by the last experiment to be acid then we may 
consider that it contains either superphosphate or dissolved 
bones. 

To the second portion of the filtrate add ammonia ; a 
white precipitate of phosphate will be formed. Allow this 
to settle and notice the colour of the liquid. If it be quite 
colourless, then the soluble phosphate was mineral super- 

1 Two or three mixtures of the more important manures should be 
provided and the student allowed to discover their constituents. 



102-103] TESTING MANURES 39 

phosphate ; if the liquid be at all brown then the soluble 
phosphate was most probably dissolved bones. From this 
experiment, therefore, we learn first, whether the manure 
contains soluble phosphate, and secondly, whether that 
phosphate was prepared from bones or from a mineral 
phosphate. 

* 102. Test for Insoluble Phosphate. — Should 
soluble phosphate have been found in paragraph ioi, we are 
pretty certain to find insoluble phosphate also. This is 
tested for in the substance saved on the filter-paper from 
the last experiment. Scrape the mud off the filter-paper 
and place in a 3 -inch evaporating-dish ; just cover the 
substance with strong hydrochloric acid and warm for a few 
minutes. When as much has dissolved as is possible fill 
the dish nearly full of distilled water and stir well. Filter. 
The residue will be the sand which was present in the 
manure. Divide the liquid which comes through into two 
portions. Boil one portion with ammonium molybdate. 
Should a yellow precipitate form, then insoluble phosphate 
was present. To the other portion add ammonia, and 
notice the colour of the precipitate. If the insoluble phos- 
phate has been derived from bones the precipitate will be 
quite white. If it has been derived from mineral phosphate 
the precipitate will probably contain phosphate of iron, and 
be more or less brown. From this experiment we learn 
whether the manure contains insoluble phosphate, and, if so, 
whether it is made from bones or mineral. 

* 103. Test for Organic Nitrogen.— Boil up a small 
quantity of the manure with water in a 3-inch evaporating- 
basin. Filter and wash with the spray from a wash- bottle ; 
keep the liquid for paragraph 105. When the liquid 
and washings have all run through, take the filter and its 
contents out of the funnel and place them in a dry evapo- 
rating-basin, and put this to dry in a steam-oven. (Whilst 
the substance is drying proceed with the next experiment) 



40 PRACTICAL AGRICULTURAL CHEMISTRY [104-106 

When quite dry, remove the substance from the filter-paper 
to a mortar, and there mix it with about three times its 
weight of soda-lime. Heat some of this mixture in an 
ignition-tube and test the evolved gases with turmeric-paper. 
A brown coloration given to the paper indicates organic 
nitrogen. The reason for the preliminary washing with 
water is to remove any sulphate of ammonia or other sub- 
stance which might contain ammoniacal nitrogen. 

* 104. Test for Ammoniacal Nitrogen.— Warm a 
little of the manure in a test-tube with caustic-potash 
solution ; test the vapour which comes off with turmeric- 
paper as directed in paragraph 86. Should the paper turn 
brown, ammonical nitrogen is present in the manure ; and 
since sulphate of ammonia is the principal substance in 
manures which contain nitrogen in this form, we may 
usually assume that the brown coloration indicates that 
sulphate of ammonia was present in the manure. 

* 105. Testfor Nitric Nitrogen.— Nitric nitrogen is 
generally added to manures in the form of nitrate of soda, 
but many natural manures contain nitrate of lime. This is 
especially the case with bat's guano. For this test use the 
clear liquid saved from paragraph 103. Follow out exactly 
the test described in paragraph 87. Should the indigo be 
bleached the manure contains nitric nitrogen. 

* 106. Test for Potash. — Heat a little of the manure 
on platinum foil in the Bunsen flame until all the carbo- 
naceous matter is burned off. Remove the ash which is left to 
a watch-glass and moisten it with hydrochloric acid. Test the 
substance in the flame on a loop of platinum wire, viewing 
the colour through an indigo-prism or a piece of cobalt-blue 
glass. Should the flame, when viewed thus, appear crimson, 
the manure contains potash. The most usual forms in 
which potash is added to mixed manures are sulphate of 
potash, muriate of potash, and kainit, which is a double 
sulphate of potash and magnesia. 



107-109] EXPERIMENTS ON FEEDING MATERIALS 41 



EXPERIMENTS ON FEEDING MATERIALS 

The experiments described below show some of the 
properties of feeding materials ; they are divided into four 
sets, viz. experiments on oil-cakes, experiments on grass, 
experiments on turnips, and experiments on cereal foods. 

Oil-cakes. 

107. The principal kinds of oil -cake are linseed cake 
and cotton cake, but many other substances are used, 
such as rape, palm-nut, and various flavouring materials. 
The chemical constituents which affect the feeding value of 
oil-cakes are much the same, whatever the seed used. 
The constituents are water, oil, albuminoids, carbohydrates, 
woody fibre, and sand, the last two forming the indigestible 
part of the cake. The meaning of the above chemical terms 
is explained as far as possible in the following experiments. 

108. Water in Oil-cakes.— Grind up a piece of lin- 
seed-cake in a mortar and place a little of the powder in a 
bulb-tube with a neck about eight inches long. Boil some 
water in a small beaker standing on a wire gauze. Now 
hold the bulb containing the cake just beneath the surface 
of the boiling water in a slanting position, so that the bulb 
and cake may be heated up to the boiling-point of water, 
whilst the rest of the tube is kept cool. In a very short 
time water-vapour will come off from the apparently dry 
cake and condense in the cooler part of the tube, where it 
may be seen to dim the inner surface of the glass tube. 

109. Oil in Oil-cakes. — Spread out a little linseed- 
cake, which has been ground up in a mortar, on a piece of 
filter-paper. Lay the paper on a clean white tile and just 
moisten the cake with ether. After it has stood for a minute 
exposed to the air, the greater part of the ether will have 
evaporated. Place the paper for five minutes in the steam- 



42 PRACTICAL AGRICULTURAL CHEMISTRY [l 10-111 

oven ; after this time brush the dry linseed-powder from its 
surface. Grease-marks will be found on the paper, showing 
that the cake contained oil. This oil not only helps in 
forming the fat of the animal feeding on it, but it also helps 
in the development of animal heat. 

1 10. Albuminoids in Oil-cakes. — Albuminoids are 
essentially the flesh-forming compounds in the cake, and 
they are distinguished from other constituents by the fact 
that they contain nitrogen. Mix a little powdered linseed- 
cake with soda-lime and heat some of the mixture in an 
ignition-tube. Ammonia will be given off, and may be tested 
for with moist yellow turmeric-paper as described in para- 
graph 85. This ammonia is formed by the action of soda- 
lime on the nitrogen of the albuminoids. 

* in. Carbohydrates in Oil-cakes. — The name 
'carbohydrate' is given to a large class of bodies containing 
the three elements, carbon, hydrogen, and oxygen. Starch, 
sugar, and dextrin are examples of carbohydrates. Most of 
these bodies, on being heated for some time with dilute sul- 
phuric acid, are converted into grape-sugar. Half fill an 
evaporating-basin with dilute sulphuric acid (the ordinary 
dilute acid used in the laboratory must be mixed with twice 
its volume of water for this experiment). Throw on to the 
surface of the acid liquid at much powdered linseed-cake as 
can be held on a penny. Boil gently over a Bunsen flame, 
supporting the basin on a tripod and pipeclay triangle. Add 
a little hot water from time to time as the liquid evaporates, 
to prevent the acid becoming too strong. When it has boiled 
for five minutes remove from the flame, allow to cool, and 
filter. Grape-sugar must now be tested for in the clear 
solution. This is done by adding potash to the acid solution 
until it is slightly alkaline, then a few drops of Fehling's 
Solution (266), and heating. The blue colour of the 
Fehling's Solution will be destroyed, and a light-red or yellow 
precipitate of cuprous oxide will be formed. 



H2-115] OIL-CAKES 43 

* 112. Woody Fibre in Oil-cakes.— The woody 
fibre and the sand are the indigestible portions of oil-cakes. 
Woody fibre may be shown to be present in oil-cake in the 
following way. 

Take as much ground linseed-cake as can be held on a 
sixpence, place in a test-tube, and fill the test-tube about one- 
third full of glycerine. Now heat very cautiously in the 
Bunsen flame until the glycerine just boils. Keep it hot 
for about a minute, then allow it to cool. Nearly fill 
the test-tube with water, warm again, and filter. The sub- 
stance left on the filter will be nearly pure woody fibre. 

* 113. Sand in Oil-cake. — Burn a little oil-cake powder 
on platinum foil over the Bunsen flame, in the same way as 
was described with bones in paragraph 97, until the ash is 
quite light-coloured. Empty the ash into a clean test-tube 
and fill it about an inch deep with dilute hydrochloric acid. 
Boil for a minute or so, then filter. Spread out the filter on 
a glass plate ; grains of sand, if present, will be seen on the 
paper. ThiS experiment may not always succeed on the 
first attempt owing to the small amount which can be 
burnt at once on a piece of foil. Two or three attempts will 
usually give some sand, especially if the same filter be used 
for all the experiments. 

114. Linseed-cake. — All the above tests are applicable 
to any kind of oil-cake, but some few tests may be per- 
formed with special kinds of cake. A pure linseed-cake 
may generally be recognised from two of its properties. It 
is highly mucilaginous, and it does not contain starch. 

115. Mucilage in Linseed-cake.— Place about a 
teaspoonful of ground linseed-cake in a 4-ounce beaker and 
half-fill the beaker with boiling water. Stir vigorously with 
a glass rod ; allow to cool. It will be found that the linseed 
has swollen up into a gummy mass. The better the cake, 
the more mucilaginous the mass will be; whilst a very 
poor cake will not swell up at all, but settle quickly to the 
bottom of the liquid. 



41 PRACTICAL AGRICULTURAL CHEMISTRY [116-119 

* 116. Testing Linseed-cake for Starch.— Pour a 

little of the gummy substance prepared in the last experi- 
ment into a test-tube and boil it. As soon as it has boiled 
cool it down by allowing the cold water from a tap to run 
over the outside of the tube. When quite cool add a few 
drops of a solution of iodine in potassium iodide and shake 
up. If the cake assume a greenish colour it is pure and 
free from starch ; if it turn deep blue or black it shows the 
presence of starch, and therefore it has been adulterated. 

117. Cotton-wool in Cotton-cake.— In the pre- 
paration of cotton-cake it is necessary to free the seed from 
cotton-wool. If this be badly done the value of the cake 
will be much impaired. 

Break up a piece of undecorticated cotton-cake, weighing 
about two ounces, as finely as possible in a mortar, then place 
it in a wire sieve having from twenty to thirty meshes to the 
linear inch. Shake the sieve until all the finer portion has 
passed through, and examine the husk which is left. Should 
the cake be an inferior one a small quantity of* cotton-wool 
will usually be found adhering to it. The wool may often 
be seen without this preliminary sifting. 

Grass and Hay 

118. Grass and Hay. — All the substances which have 
been shown to occur in oil-cakes may be found in grass. 
Some of these, however, such as oil, occur in such small 
quantities that it would require far more delicate experiments 
than those detailed in these pages to show their presence. 
The following experiments, however, are instructive and 
should be performed. 

119. Albuminoids in Grass.— Cut up a little grass 
(or hay) as finely as possible with a pair of scissors and 
grind it up in a mortar with a little sharp sand. This will 
render it sufficiently fine to mix readily with soda-lime. 
Mix it with an equal quantity of soda-lime and heat a little 



120-122] GRASS AND HAY 45 

of the mixture in an ignition-tube. The albuminoids will 
give off ammonia. See paragraph 85. 

120. Chlorophyll in Grass.— Chlorophyll is the green 
colouring matter which occurs in grass. Cut up a handful 
of grass with scissors and place it in a mortar ; just cover 
the grass with methylated spirit and grind it gently with the 
pestle for a few minutes. Now filter the substance through 
a piece of linen stretched loosely over the top of a beaker 
and tied. The liquid which comes through will be quite 
green. Pour a little of this liquid into an evaporating-basin 
and leave it on a steam-bath to evaporate. Do not evaporate 
over a Bunsen flame, or it will catch fire. When all the 
spirit has evaporated a film of green chlorophyll will be 
found at the bottom of the dish. Now squeeze all the 
spirit out of the substance left in the linen and wash it with 
a little ether. The residue left in the linen will be found to 
be light-coloured, and if the washing be continued will 
eventually become colourless. 

121. Ash in Grass. — Place a handful of hay, or grass, 
dried in the steam-oven, on a porcelain tile and light it with 
a match. When it has stopped burning gather all the ash 
on to a piece of platinum foil and heat it until it loses its 
black colour. Sometimes the ash thus left will be green : 
this is due to the presence of manganese, but more often it 
will be white or light-brown. Keep the ash for the next 
experiment. 

* 122. Alkalies in Grass.— The ash of grass contains 
both potash and soda, which will probably fuse in the 
Bunsen flame, and so cause the ash to adhere to the 
platinum foil. Roll up the foil, with the ash adhering to it, 
and place in a test-tube. Just cover it with distilled water 
and boil. Now take a drop of the solution thus prepared, 
on the end of a glass rod, and touch a piece of red litmus- 
paper with it. Where the liquid touches the paper the red 
will be turned to blue, showing the presence of an alkali 



46 PRACTICAL AGRICULTURAL CHEMISTRY [123-126 

Keep the test-tube containing the platinum foil and liquid 
for the next experiment. 

* 123. Phosphates in Grass.— To the water in the 
test-tube (paragraph 122) add an equal volume of dilute 
nitric acid and warm. Decant the liquid into another clean 
test-tube, leaving the platinum foil behind. To the clear 
liquid so obtained add an excess of ammonium molybdate 
solution and boil ; a yellow precipitate will appear, showing 
that the grass contained phosphates. 

Roots 

124. Turnips.— Roots, such as turnips, swedes, and 
mangels, differ from the foods which have been considered, 
in that they contain a very much larger proportion of water 
and a greater quantity of sugar. When the water is squeezed 
out of the roots it brings the sugar and other soluble sub- 
stances with it. Hence the components of a turnip may be 
divided into two kinds : the soluble, which with the water 
constitute juice, and the insoluble, which go by the name of 
crude fibre. The crude fibre is very much like hay in its 
constitution ; therefore the experiments here described are 
intended only to show the properties of the juice. 

125. Juice in Turnips.— Cut a turnip up into six 
sections with a large knife. Grate up one or two of these 
sections on a bread-grater, allowing the pulp to fall on to a 
piece of linen stretched over a porcelain tile. When a good 
handful of pulp has been thus prepared, fold it up in the 
cloth and squeeze out the juice into a beaker. Throw away 
the fibre left in the cloth and with the juice perform the 
experiments described in paragraphs 126 and 129. 

126. Sugar in Turnips. — Taste a little of the juice. 
It has the flavour of raw turnip, but is nevertheless very 
sweet. Pour sufficient juice into a clean test-tube to fill 
about half an inch of the tube. Dilute this with about four 
times its volume of water, then add about an equal volume 



127-129] ROOTS 47 

of strong lead acetate solution. Shake up well and allow 
to stand for quarter of an hour to settle. Whilst it is settling 
go on with the next experiment. At the end of the quarter 
of an hour the liquid in the test-tube will have become quite 
clear, except for a thick deposit of white material at the 
bottom. Pour off a little of the clear liquid into another 
test-tube and add caustic potash solution ; a white precipi- 
tate will be caused. Add more caustic potash until the pre- 
cipitate is redissolved ; then add a little Fehling's Solution, 
and boil. A yellow or bright red precipitate will be formed, 
which shows the presence of sugar. 

* 127. Cane Sugar and Grape Sugar.— The sugar 
found in swedes and turnips is a different substance from 
the sugar which we use for sweetening purposes. The former 
is glucose or grape sugar, the latter is cane sugar. The 
properties of these two kinds of sugar are best studied by 
using the pure substances. Dissolve a little cane sugar in 
water in a test-tube. In another test-tube make a solution 
of glucose ; to each of these add a little Fehling's Solution 
and boil. The glucose will give a reddish precipitate, whilst 
the cane sugar will not. 

* 128. Inversion of Cane Sugar. — Make a solution 
of cane sugar in a test-tube half full of water ; add a few 
drops of strong hydrochloric acid and boil well. After 
boiling add a little potash to neutralise the acid, then a little 
Fehling's Solution, and boil again. A precipitate will now 
be formed, showing that the cane sugar has been changed 
to glucose by boiling with the acid. 

* 129. Albuminoids in Turnip Juice.— One of the 
properties of albuminoids is that they are rendered insoluble 
by carbolic acid. Pour a tablespoonful of turnip juice into 
a beaker and add two drops of strong carbolic acid solution 
(80 per cent.) Allow the beaker to stand overnight The 
albuminoids will settle, leaving the liquid clear. 



48 PRACTICAL AGRICULTURAL CHEMISTRY [130-132 

Cereal and Leguminous Foods 

130. The most important cereal and leguminous foods 
are wheat, barley, oats, maize, peas, and beans. These focds 
should be tested for their main constituents, viz. water, oil, 
albuminoids, and carbohydrates, by the methods described 
in paragraphs 108, 109, no, and m; noting at the same 
time the relatively large quantities of albuminoids in peas, 
and beans, and of carbohydrates in wheat, barley, oats, 
and maize. Wheat differs from other foods in containing 
a nitrogenous substance, called gluten, which gives wheaten 
flour the peculiar property of kneading with water. All the 
cereals contain large quantities of starch. 

131. Starch in Flour. — The test for starch has already 
been given (116). Wet a little flour with water so as to make 
a thin cream. Boil a little water in a test-tube, and when 
it is boiling briskly add a drop of the cream, then boil for a 
few seconds. Cool the liquid by allowing a current of cold 
water to flow from a tap round the outside of the test-tube, 
and when quite cold add a drop of iodine solution. An 
immediate deep-blue coloration indicates the presence of 
starch. The colour will appear almost black, but if a drop 
of the dark liquid be mixed with a large quantity of water 
it will be seen that it really is of a dark-blue colour. 

132. Gluten in Wheaten Flour.— Mix a handful 
of wheaten flour with enough water to form a stiff paste. 
Knead it well in the fingers, then wrap it up in a small 
piece of muslin and hold it in a gentle stream of water from 
a tap, kneading it all the time. The starch will be gradually 
washed away through the muslin, leaving a dark-coloured 
indiarubber-like mass. This is gluten, which gives a mixture 
of flour and water its peculiar adhesiveness. 



133-137] DAIRY PRODUCE 49 

DAIRY PRODUCE 

Milk 

133. Action of Acid on Milk.— Half fill a test-tube 
with milk. Add about six drops of dilute sulphuric acid 
and shake. Allow the tube with its contents to stand for 
five minutes. At the end of that time the milk will be seen 
to have curdled. The acid has coagulated the soluble 
albuminoids, rendering them insoluble, and thus forming 
clots which separate out from the milk. 

134. Fat in Milk.— Filter the curdled milk and save 
the clear filtrate (136). Spread out the filter-paper which 
contains the 'curd' on a glass plate and place in the 
steam-oven to dry. When it has got quite dry the fat will 
melt out of the curd, and form grease stains on the filter- 
paper. 

135. Albuminoids in Milk.— The residue left on the 
filter-paper, after the fat has been melted out as described 
in the last experiment, is principally albumen and casein. 
Both these substances contain nitrogen, which may be 
tested for by scraping this residue off the filter, mixing with 
soda-lime, and heating in an ignition-tube as described in 
paragraph 85 ; ammonia will be given off. 

136. Sugar in Milk. — The clear liquid which has 
been saved (134) contains sugar. This sugar is different 
from either cane sugar or glucose, and goes by the name 
of lactose, or milk sugar. It has an action, however, on 
Fehling's Solution (266) similar to that of glucose. Add 
to the clear liquid in the test-tube (134) a little potassium 
hydrate solution until the liquid is no longer acid, then add 
Fehling's Solution and boil; a yellow precipitate will be 
formed, indicating the presence of sugar. 

137. Natural Acidification of Milk.— If milk is 
allowed to stand in the air, certain bacteria will gradually 



50 PRACTICAL AGRICULTURAL CHEMISTRY ("138-139 

oxidise the lactose, producing lactic acid. This acid will 
curdle the milk, as described in paragraph 133. 

The milk may be prevented from ' going sour ' in various 
ways : 

(a) By heat or cold, thus destroying the bacteria or 
suspending their activity. 

(6) By adding an alkali, e.g. carbonate of soda, so 
neutralising the acid as it is produced. 

(c) By adding a 'germicide,' such as borax, boracic 
acid, or formalin, to poison the bacteria. 

As, however, it is illegal to add any foreign substances 
to milk, heat and cold are the only two methods officially 
recognised. 

138. Preservation of Milk.— Half fill six test-tubes 
with milk, and treat as follows : Allow the first portion 
to remain in the test-tube stand without any further treat- 
ment. Boil the second portion and place it also in the 
test-tube stand. To the third add a few drops of forma- 
lin (40 per cent, formic aldehyde) ; to the fourth add a 
few drops of strong sodium carbonate solution ; and to 
the fifth a few drops of borax solution. The sixth must 
be placed in an ice-chest so that it may remain at a low 
temperature. 

The milk should be examined daily, and the order in 
which the different samples turn sour noted. The record 
so obtained will give an indication of the efficiency of the 
various methods employed. 

139. Tests for Preservatives in Milk.— The pre- 
servatives usually found in milk are boracic acid, borax, 
and formalin. The following tests should be applied to 
samples of fresh milk; if no results are obtained, they 
should be repeated with samples treated as described in 
paragraph 138. 

Boracic Acid or Borax. — Make the milk alkaline with 
lime water, evaporate to dryness and ignite until the re- 



140-141] DAIRY PRODUCE 5 1 

sidue becomes white. Warm the ash with a few drops of 
strong hydrochloric acid. Evaporate the filtrate to dryness 
and dissolve the residue in a few drops of water. Place in 
the dish a piece of turmeric paper and evaporate to dry- 
ness on the water-bath. A brown colour which turns 
dark green with ammonia indicates boracic acid. 

Formaldehyde. — Place about 10 c.c. of the milk and an 
equal volume of strong hydrochloric acid in an evaporating 
basin. Add one drop of very dilute ferric chloride. Heat 
slowly with constant stirring to a temperature a little below 
boiling. A violet colour indicates the presence of formalin. 
Care should be taken not to boil the milk or the colour may 
be destroyed. 

Note. — This test may be used for the presence of 
formalin in other substances than milk, but as the proteids 
of milk take part in the reaction a few c.c. of pure milk 
must be added to the suspected liquid before the test is 
applied. 

Butter 

Butter consists principally of the fat of the milk, but 
it also contains small quantities of curd, salt, and water. 

140. Water in Butter. — Place as much butter as 
you conveniently can in a test-tube. Then hold the tube in 
hot water until the butter is completely melted. Note the 
appearance of the tube. The pure butter-fat will form a 
clear top layer. Beneath this will come a cloudy layer 
containing the curd and salt, and beneath this, again, will 
be seen drops of water. 

141. Curd in Butter. — Whilst the butter is still hot 
pour it on to a dry filter-paper in a funnel. Place the funnel 
in the neck of a 4-oz. conical flask and place the whole 
arrangement in the steam-oven (22). This will serve to 
keep the butter melted whilst it is filtering. In a few 
minutes nothing will be left on the paper but the curd and 

£2 



52 PRACTICAL AGRICULTURAL CHEMISTRY [142-144 

salt with a little water. The curd may be shown to contain 
nitrogen by heating with soda-lime as described in para- 
graph 85. 

142. Salt in Butter. — Hold the greasy filter-paper 
prepared in the last experiment, together with its contents, 
by means of a pair of crucible tongs over a porcelain tile, 
then light it with the flame of a Bunsen. When it has 
quite burned, and the ash has fallen on to the tile, sweep it 
up into a test-tube. Half fill the test-tube with water and 
boil for a minute or two, then filter. The clear liquid which 
comes through will contain any salt which was present in 
the original butter. To test for salt add a drop of dilute 
nitric acid and a few drops of silver nitrate solution. A 
white precipitate will be formed (see paragraph 201). 

Cheese 

Cheese contains exactly the same constituents as butter, 
but in different proportions. Thus whilst the butter consists 
principally of fat the cheese consists chiefly of curd. 

143. Fat in Cheese. — Place a few cheese-parings on 
a piece of filter-paper and heat in the steam-oven (22). The 
fat in the cheese will melt and grease the paper. 

144. Albuminoids in Cheese.— Heat a little of the 
cheese with soda-lime as described in paragraph 85. The 
presence of nitrogen is shown by the evolution of ammonia. 



145-146] QUALITATIVE ANALYSIS 53 



SECTION IV 

QUALITATIVE ANALYSIS OF THE BODIES 
COMMONLY OCCURRING IN SOILS AND MANURES 

Introductory Remarks 

145. This section treats only of those bodies which 
occur in soils, manures, and agricultural products, namely, 
the carbonates, sulphates, chlorides, nitrates, nitrites, sili- 
cates, and phosphates of the metals aluminium, iron, manga- 
nese, calcium, magnesium, potassium, sodium, and ammo- 
nium, together with organic carbon, nitrogen, chlorine, and 
sulphur. 

Chemical formulae are freely used, but not unless the 
name of the compound has already been mentioned in the 
same paragraph. 

In some instances the chemical changes are expressed 
by equations. 

146. The systematic name of an inorganic compound 
such as a salt is usually a double name, the metal forming 
one portion, and the acid portion (called the acid-radical) 
the other portion of the name. Thus sodium on being 
added to sulphuric acid would form sodium sulphate : — 

Na 2 + H 2 S0 4 

Sodium Sulphuric 

acid 

Hence the names of both metal and acid, or some modifi- 
cation of them, are included in the name of the compound 
formed. In analysis it is found convenient to test for the 
metal and the acid-radical separately. In the above case of 



sa 


Na 2 S0 4 


+ H 2 




Sodium 


Hydrogen 




sulphate 





54 PRACTICAL AGRICULTURAL CHEMISTRY [147-150 

sodium sulphate, the sodium (Na) would first be tested for 
by the sodium test (186), and then the acid radical (S0 4 ) 
would be tested for by the sulphate test (194). 

147. It will be noticed that the name of a suitable sub- 
stance for performing the tests upon is given at the head 
of each series of reactions. Thus, when testing for sodium, 
the most suitable substance to use is sodium chloride 
(NaCl). The reagent to be added is given immediately 
after the paragraph number. 

148. Entry in Note-book. — A note-book of quarto 
size should be used. A concise account of each experiment 
or test should be entered directly it is made. Neat pencil 
entry will suffice. The entry should not be considered 
complete until after it has been examined and initialled by 
the teacher. 

The following tests for sodium will serve for an example 
of entry : — 

Sodium (Na). Used NaCl. 

% 
Dipped a platinum wire into the solution and held in Bunsen flame : 

golden-yellow flame-coloration ; not seen through prism. 

Heated the solid in ignition-tube : decrepitated and finally fused ; 

no sublimate formed. 



General Rules to be Observed whilst Working 

149. Before commencing work see that the reagent- 
bottles are full ; filter any liquids that require it. Clean the 
apparatus if necessary. It is far better to put everything 
away clean. Keep the bench scrupulously clean during 
work. 

150. In cleaning apparatus, glass and porcelain can 
usually be cleansed by washing with a brush. If this fails 
caustic alkalies or acid may be requisite. Failing these, 
rubbing or shaking with a little sea-sand will usually suffice. 



151-158] TESTS FOR THE METALS 55 

Metal vessels are best cleaned with a little moistened sea- 
sand. 

151. When using a reagent bottle the bottle should be 
grasped by the right hand, and the stopper taken out by the 
left hand. After use replace the stopper and put back the 
bottle on the shelf. In this way the bottle is not placed on 
the bench at all, and much time is saved. 

152. Brass crucible tongs must not be used for holding 
vessels containing acid liquids, or the brass may be dissolved 
and introduced into the liquid. Platinum crucibles must 
not be handled by brass tongs when red-hot. 

153. When heating liquids in porcelain or glass the 
flame should never reach higher than the level of the liquid, 
or the vessel will break. 

154. Liquids only are to be poured down the sink ; 
solids and filter-papers should be placed in boxes or baskets. 

155. Crucibles or vessels containing solids are best 
heated on pipeclay supports, flasks containing liquids on 
wire gauze. 

156. When an operation is unfinished the vessels con- 
taining the substances should be labelled before putting 
them away. Never trust to memory in these matters. 

157. Before commencing any operation read carefully 
through the whole of the description. 



REACTIONS FOR THE METALS 



ALUMINIUM (Al).— Use alum, AlK(S0 4 ) 2 .i2H 2 0, or 
ammonia-alum, AlNH 4 (S0 4 ) 2 .i2H 2 0, solution. 

158. Ammonium Hydrate (NH 4 OH) gives a white 
gelatinous precipitate of aluminium hydrate, Al(OH) 3 . 
This precipitate is somewhat soluble in a larger excess of 



$6 PRACTICAL AGRICULTURAL CHEMISTRY [159-164 

NH 4 OH ; hence this reagent should only be added in slight 
excess. Al(OH) 3 is readily soluble in hydrochloric acid 
(HC1) and in acetic acid (HA). 

159. Potassium Hydrate (KHO) or Sodium 
Hydrate (NaHO) when added drop by drop gives the 
same precipitate as NH 4 OH, but it is readily soluble in 
excess of these reagents. By adding ammonium chloride 
(NH 4 C1) in large excess to this solution, and boiling, the 
precipitate will be thrown down again. 

160. Ammonium Sulphide, (NH 4 ) 2 S, gives the 
same precipitate as NH 4 OH with evolution of sulphuretted- 
hydrogen gas. This precipitate is insoluble in excess of 
the reagent. 

IRON (Fe).— Use ferrous sulphate (FeS0 4 .7H 2 0) and 
ferric chloride (Fe 2 Cl 6 ) solutions. 

161. Note Iron forms two classes of compounds, known respec- 
tively as ferrous and ferric compounds. It is often necessary that the 
analyst should ascertain whether one or both of these two classes are 
present in a substance containing iron. Tests are here given for both 
classes. 

FERROUS SALTS. — Use ferrous sulphate 
(FeS0 4 . 7 H 2 0). 

162. Ammonium Hydrate (NH 4 OH) or potassium 
hydrate (KHO) gives a dingy green precipitate of ferrous 
hydrate, Fe(OH) 2 , which becomes brown on exposure to 
the air. It is soluble in hydrochloric acid (HC1), and in- 
soluble in excess of KHO. 

163. Ammonium Sulphide, (NH 4 ) 2 S, gives a black 
precipitate of ferrous sulphide (FeS), soluble in hydro- 
chloric acid (HC1). 

164. Potassium Ferrocyanide, K 4 Fe(CN) 6 , gives 
a light- blue precipitate, becoming dark on exposure to the 
air. 



165-173] TESTS FOR THE METALS 57 

165. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives 
a dark-blue precipitate, soluble in HC1. 

166. Potassium Sulphocyanide (KCNS) produces 
no change in ferrous solutions if free from ferric salts. 



FERRIC SALTS.— Use ferric chloride (FeCl) 3 . 

167. Ammonium Hydrate (NH 4 OH) or Potas- 
sium Hydrate (KHO) gives a reddish-brown flocculent 
precipitate of ferric hydrate, Fe(OH) 3 , soluble in hydro- 
chloric acid (HC1), insoluble in excess of AmHO and KHO. 

168. Ammonium Sulphide, (NH 4 ) 2 S, gives a black 
precipitate of ferrous sulphide (FeS), which contains white 
sulphur (S). The black FeS hides the white S from view. 

169. Potassium Ferrocyanide, K 4 Fe(CN) 6 , gives 
a dark-blue precipitate of Prussian blue, soluble in oxalic 
acid, turned brown by potassium hydrate (KHO). 

170. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives 
no precipitate, but the liquid darkens in colour. 

171. Potassium Sulphocyanide (KCNS) gives a 
blood-red coloration, which may be destroyed by the addi- 
tion of mercuric chloride (HgCl 2 ). 

172. By heating a small portion of solid ferric or 
ferrous salt on the borax bead (27) in the outer blowpipe 
flame a reddish-brown colour is obtained whilst the bead is 
hot, which fades on cooling. The inner flame gives an 
olive-green bead both hot and cold. 



MANGANESE (Mn).— Use manganous sulphate 
(MnS0 4 ) solution. 

173. Ammonium Hydrate (NH 4 OH) gives a white 
precipitate of manganous hydrate, Mn(OH) 2 , which quickly 



53 PRACTICAL AGRICULTURAL CHEMISTRY [174-180 

turns brown in the air. This is best seen by pouring the 
precipitate on to a filter-paper. If, however, ammonium 
chloride (NH 4 C1) has been added before the NH 4 OH, the 
precipitate will not be formed. 

174. Potassium Hydrate (KHO) gives the same 
precipitate as ammonium hydrate, even in the presence of 
AmCl. 

175. Ammonium Sulphide, (NH 4 ) 2 S, gives a flesh- 
coloured precipitate of manganous sulphide (MnS). This 
precipitate often appears yellow from the excess of the 
(NH 4 ) 2 S, which has been added. On filtering off this liquid 
the true colour may be seen. The colour of the precipi- 
tate darkens on standing in the air. 

176. If a solid substance containing manganese be 
mixed with three times its weight of sodium carbonate 
(Na 2 C0 3 ), and a third as much potassium nitrate 
(KNO3), an d tn e mixture fused on platinum foil, a bluish- 
green mass is obtained on cooling. 

177. Borax Bead (27). — In the outer flame violet 
whilst hot, amethyst when cold. In the inner flame colour- 
less both hot and cold. 



CALCIUM (Ca).— Use calcium chloride (CaCl 2 '6H 2 0) 
solution. 

178. Ammonium Carbonate, (NH 4 ) 2 C0 3 , added 
after ammonium chloride (NH 4 C1) gives a white precipitate 
of calcium carbonate (CaC0 3 ), soluble in acetic acid. 

179. Ammonium Oxalate, (NH 4 ) 2 C 2 4 , gives a 
white precipitate of calcium oxalate (CaC 2 4 ) soluble in 
hydrochloric acid (HC1), and insoluble in acetic acid (HA). 

180. Sulphuric Acid (H 2 S0 4 ) gives a white preci- 
pitate of calcium sulphate (CaS0 4 ), which forms at once in 
strong solutions, but only on being boiled, in dilute solutions. 



181-187] TESTS FOR THE METALS 59 

This precipitate is slightly soluble in water, but less so in 
alcohol. If the precipitate is not formed on boiling, it will 
come down on cooling and adding excess of alcohol. 

181. Flame Coloration (26).— If a clean piece of 
platinum wire is dipped into the liquid, and then held in 
the Bunsen flame, a bright reddish-yellow colour will appear. 



MAGNESIUM (Mg). — Use magnesium sulphate 
(MgS0 4 .7H 2 0) solution. 

182. Sodium Phosphate (Na 2 HP0 4 ) added after 
ammonium chloride (NH 4 C1) and ammonium hydrate 
(NH 4 OH) gives a white crystalline precipitate of magnesium- 
ammonium phosphate (MgNH 4 P0 4 .6H 2 0), soluble in acids. 

183. Potassium Hydrate (KHO) gives a white pre- 
cipitate of magnesium hydrate, Mg(OH) 2 , soluble in acids. 

184. Ammonium Hydrate (NH 4 OH) gives the 
same precipitate as potassium hydrate ; but if ammonium 
chloride (NH 4 C1) be added previously, this precipitate will 
not form. 

185. Ammonium Carbonate (NH 4 ) 2 C0 3 gives a 
white precipitate of basic magnesium carbonate in strong 
solutions. Ammonium chloride (NH 4 C1) prevents the for- 
mation of this precipitate. 



SODIUM (Na). — Use sodium chloride (NaCl) solution. 

186. Flame Coloration (26). — Intense yellow. This 
colour is almost invisible when viewed through the indigo 
prism or a thick piece of cobalt-blue glass. 

187. Solid sodium chloride heated in an ignition-tube 
generally decrepitates and flies out of the tube ; but if it is 
perfectly dry it will fuse, giving off no fumes. 



60 PRACTICAL AGRICULTURAL CHEMISTRY [188-193 

POTASSIUM (K). — Use potassium chloride (KG) 
solution. 

188. Platinum Chloride (PtCl 4 ) added to some of 
the potassium chloride in a watch-glass and stirred with 
a glass rod, gives a yellow crystalline precipitate of 
potassium platinum chloride (K 2 PtCl 6 ). The precipitate 
forms only in moderately strong solutions, and is hastened 
by the addition of alcohol. 

188a. Sodium Picrate added to a little KC1 solution 
placed in a watch-glass gives golden yellow needle-like 
crystals of potassium picrate. The reaction is promoted 
by addition of alcohol and stirring. 

189. Flame Coloration (26).— Pale violet. When 
viewed through the indigo prism or cobalt-blue glass the 
colour appears crimson. This colour is seen through the 
prism in the presence of sodium salts. 

190. Potassium chloride heated on platinum foil behaves 
exactly like sodium chloride. 



AMMONIUM (NHj). — Use ammonium chloride 
(NH 4 C1) solution, 

191. Potassium Hydrate (KHO) poured either into 
the solution or on to some solid ammonium chloride in a 
test-tube and heated, gives off ammonia gas (NH 3 ), which 
may be recognised by its smell, or by holding a piece of 
moistened yellow turmeric-paper over the mouth of the test- 
tube, when it will be turned brown. 

192. Platinum Chloride (PtCl 4 ) stirred in a watch- 
glass with the solution gives a yellow crystalline precipitate. 

192a. Sodium Picrate, when stirred with AmCl 
solution, gives golden-yellow needle-like crystals (188a). 

193. Solid ammonium chloride, if heated in an ignition- 
tube, volatilises completely, and forms a white sublimate on 
the cold part of the tube. 



194-197] TESTS FOR ACID-RADICALS 6l 



REACTIONS FOR THE ACIDS. 



SULPHATE ("S0 4 ). — Use sodium sulphate 
(Na 2 S0 4 .i2H 2 0) solution. 

194. Barium Chloride (BaCl 2 ) gives a white precipi- 
tate of barium sulphate (BaS0 4 ), insoluble in acids. 



CARBONATE ("CO a ).— Use sodium carbonate 
(Na 2 C03.ioH 2 0) solution. 

195. Hydrochloric Acid (HC1) causes carbon dioxide 
gas (C0 2 ) to come off with effervescence. This gas may 
be recognised either by dipping a glass 
rod into lime-water and holding the 
wet end of it just inside the test-tube ; 
the adhering lime-water will be ren- 
dered milky from the formation of cal- 
cium carbonate (CaC0 3 ) ; or better by Fig. 23 
pouring the C0 2 gas into another test-tube containing a 
little lime-water (fig. 23), and then shaking up, when the lime- 
water will become milky. 




NITRITES ('N0 2 ).— -Use potassium nitrite (KN0 2 ) 
solution. 

196. Dilute Sulphuric Acid (H 2 S0 4 ) on warming 
gives off brown nitrous fumes. 

197. Potassium Iodide (KI) Solution and several 
drops of starch solution on addition to the liquid made acid 
with acetic acid gives a deep-blue coloration. 



62 PRACTICAL AGRICULTURAL CHEMISTRY [.198-203 

NITRATE (N0 8 ).— Use potassium nitrate (KN0 3 ). 

198. Ferrous Sulphate (FeS0 4 ) Solution when 

carefully added to the above solution, previously 

mixed with its own volume of strong sulphuric 

acid and cooled, will form a brown ring where 

the two layers join (fig. 24). This brown colour 

is destroyed by heat ; hence the tube must be 

kept quite cold during this test. 

109. Copper Turnings (Cu) added, after 

acidifying with strong sulphuric acid (H 2 S0 4 ), 

gives off brown fumes either at once or on 

warming the tube. 

200. Heated with indigo and sulphuric acid 

the indigo is bleached. The most accurate 

method of applying this test is described in 

paragraph 87. 
Fig. 24 r ° r 



CHLORIDE ('Cl).-Use sodium chloride (NaCl) solution. 

201. Silver Nitrate (AgN0 3 ) gives a pure white pre- 
cipitate of silver chloride (AgCl), soluble in ammonium 
hydrate (NH 4 OH), and insoluble in nitric acid (HN0 3 ). 

Filter off a little of the precipitate and expose the filter- 
paper containing the precipitate near a window : it will be 
darkened by the action of the light. 

202. Strong Sulphuric Acid (H 2 S0 4 ) warmed with 
solid sodium chloride gives off copious fumes of hydro- 
chloric acid (HC1), which redden blue litmus-paper. 

203. The solid mixed with manganese dioxide (Mn0 2 ) 
and strong sulphuric acid gives off a green gas, chlorine (CI), 
which bleaches moist red litmus-paper. 



204-210] TESTS FOR ACID-RADICALS 63 

PHOSPHATE ("'P0 4 ).— Use sodium-hydrogen-phosphate 
(Na 2 HP0 4 .i2H 2 0) solution. 

204. Magnesium Sulphate (Mg 2 S0 4 ) to which 
has been added ammonium chloride (NH 4 C1) and a 
little ammonium hydrate (NH 4 OH), gives a white crystal- 
line precipitate of magnesium - ammonium phosphate 
(MgNH 4 P0 4 .6H 2 0), soluble in acids. 

205. Ferric Chloride (FeCl 3 ) added after acetic 
acid and sodium acetate gives a pale yellow precipitate of 
(erric phosphate (FeP0 4 ), soluble in hydrochloric acid. 

206. Ammonium Molybdate (NH 4 HMo0 4 ) when 
warmed with a little phosphate solution gives a yellow 
precipitate. The ammonium molybdate should be in large 
excess, and the solution should be acidulated with nitric acid. 

207. Silver Nitrate (AgN0 3 ) gives a yellow precipi- 
tate, soluble in ammonium hydrate (NH 4 OH) or in nitric 
acid (HN0 3 ). 



SILICATE (""Si0 4 ).— Use sodium silicate (Na 2 Si0 3 ) solu- 
tion for liquid, and finely ground sand (Si0 2 ) for solid. 

208. Hydrochloric Acid (HC1) gives a gelatinous 
precipitate of silicic acid (H 4 Si0 4 ). This, however, some- 
times remains in solution, in which case the liquid should 
be evaporated to dryness in a basin, moistened with strong 
hydrochloric acid, and boiled with water. An insoluble 
residue of silica (Si0 2 ) will remain. 

209. If solid silica (Si0 2 ) be fused into a bead of sodium 
carbonate it causes the melted bead to froth, from the 
liberation of carbon dioxide. 

210. If solid silica be fused into a bead of microcosmic 
salt (NaNH 4 HP0 4 ) it is not dissolved, but floats about in 
semi-transparent particles. 



64 PRACTICAL AGRICULTURAL CHEMISTRY [211-215 



TESTS FOR CARBON, NITROGEN, CHLORINE, 
AND SULPHUR IN ORGANIC COMPOUNDS 



CARBON (C).— Use sugar. 

211. Heated on platinum foil, carbonaceous substances 
generally blacken, from the separation of carbon. On con- 
tinued heating the black substance burns away. 

212. Copper Oxide (CuO), when heated with any 
substance containing carbon, sets free carbon dioxide. To 
perform this experiment mix a little sugar with three times 
its bulk of copper oxide and place at the bottom of a dry 
test-tube ; cover with a little CuO. Fit a tube bent twice 
at right angles through the cork ; let this tube dip into 
another test-tube containing lime-water, and heat the mix- 
ture. The lime-water will become milky. 

NITROGEN (N).— Use urea, CO(NH 2 ) 2 . 

213. Soda-lime, on heating with most nitrogenous 
substances, liberates ammonia, which may be recognised 
by its smell and its action on turmeric-paper. 

214. Sodium (Na) forms sodium cyanide when heated 
in a test-tube with most organic nitrogenous substances. 
On extracting with water, filtering, and adding a solution of 
ferrous sulphate containing a drop of ferric chloride and 
finally hydrochloric acid in excess, a precipitate of Prussian 
blue is left. 

CHLORINE (CI).— Use chloral hydrate. 

215. Lime (CaO) when heated in a test-tube with an 
organic-chlorine compound forms calcic chloride (CaCl 2 ). 
On dissolving in dilute nitric acid (HN0 3 ), filtering, and 
adding silver nitrate (AgN0 3 ), a white precipitate is formed. 



216-221] PRELIMINARY EXAMINATION FOR METALS 65 

SULPHUR (S).— Use albumen. 

2l6. Boiled with dilute hydrochloric acid (HC1) and 
potassic chlorate (KC10 3 ) until the solution is colour- 
less, sulphuric acid is formed, which may be tested for by 
barium chloride, when a white precipitate will be formed 
(i94). 



TABLES FOR QUALITATIVE ANALYSIS 

The following Tables give the order in which the tests should 
be applied for the metals and acid-radicals treated of in 
the preceding pages. A number of analyses should be 
performed by the student including limestone, different 
varieties of soils, simple and complex manures, and the 
ashes of plants. 

TABLE I.-PRELIMINARY EXAMINATION OF 
SOLID SUBSTANCES FOR METALS 

217. Carefully note the appearance of the solid, such as shape, 
colour, smell, hardness, &c. 

218. If a solution is being analysed it will be necessary, before 
proceeding with this examination, to evaporate a portion of the liquid 
to dryness and to use the dry residue. 

219. Before applying the following tests finely powder some of 
the substance, using an agate mortar if it should be very hard. 



Experiment 


Observation 


Inference 


220. Expt. I.— Heat 


I. The substance fuses 


Salts of K and 


in a small test-tube 


and solidifies on cool- 


Na or cer- 


or igniMon-tube 


ing 


tain salts of 
Ca and Mg 




2. It sublimes 


Ammonium 
salts 


821. — Confirm by heating 


Ammonia gas is given off which 


Ammonium pre- 


with potassium hydrate 


turns moistened turmeric- 


sent 


solution 


paper brown 






3. Water is given off 


Presence of 

combined 

water 




4. It blackens 


Presence of 






organic matter 



£6 PRACTICAL AGRICULTURAL CHEMISTRY [222-227 



"Experiment 


Observation 


Inference 


222. Expt. 2.— Take 


I. Intense yellow colora- 


Sodium 


up a little of the 


tion 


Potassium also 


substance on a loop 


A crimson flame is seen 


present 


of platinum wire, 


when viewed through 




moisten with strong 


cobalt glass or indigo 




HC1, and hold in 


prism 




the Bunsen flame 


2. Pale violet, crimson 
through indigo prism 


Potassium 




3. Orange-red coloration 


Calcium 


223. Expt. 3.— Heat 


Colour of Beads 




a small quantity of 
the substance in a 


Outer 


Inner 




borax bead first in 


1. Brown, 


Olive 


Iron 


the outer then in 


hot and 


green, hot 




the inner blowpipe 


yellow cold 


and cold 




flame 










2. Reddish 


Colourless, 


Manganese 




purple, hot 


hot and 






and cold 


cold 





If organic matter is present the following additional 
tests should be performed : — 

224. Carbon. — Heat with CuO (212). Evolution of 
CO 2 shows presence of carbon. 

225. Chlorine. — Heat with lime (215), dissolve in 
dilute HNO3, an d test with AgN0 3 solution ; a white pre- 
cipitate indicates presence of chlorine. 

226. Sulphur. — Heat with dilute hydrochloric acid 
and KCIO3 (216) ; filter, and add BaCl 2 solution ; a white 
precipitate shows presence of sulphur. 

22TJ. Nitrogen. — If ammonium salts are absent (221) 
heat the substance with soda-lime ; the evolution of 
ammonia gas (213) indicates organic nitrogen. 

If ammonium salts are present heat the substance with 
KHO solution until ammonia gas ceases to be evolved ; 
filter, mix the residue with soda-lime, and heat in an 



228-235] WET EXAMINATION FOR METALS 67 

ignition-tube ; evolution of ammonia indicates presence of 
organic nitrogen. 

WET EXAMINATION FOR METALS 

228. If the substance be a solid it is first of all necessary 
to bring it into solution. 

Finely powder the substance in a mortar. If the sub- 
stance is very hard an agate mortar must be used. 

229. Process of Solution.— Boil up as much of the 
powdered solid with distilled water as will cover a shilling. 
If the substance dissolves proceed with the analysis. If 
some remains undissolved heat another portion of the solid 
with dilute hydrochloric acid for several minutes. If all 
dissolves proceed with the analysis. If all does not dis- 
solve heat a fresh portion with strong hydrochloric acid to 
which has been added a little strong HN0 3 ; dilute, filter 
if necessary, and proceed with the analysis. If any residue 
is left it will require treating as an insoluble substance by 

paragraph 250. 

NOTES TO TABLE II. 

230. — If the temperature of ignition be too high, insoluble A1 2 0, 
and Fe 2 3 will be formed which will not redissolve when treated with 
HC1. If organic matter is present the dish should be gently heated 
with a small flame until the black carbonaceous matter is burnt away. 

231. — If AmCl is added in insufficient quantity Mn and Mg may 
be precipitated with AmHO. If AmCl is added in very large quantity 
MnS is prevented from precipitating when Am 2 S is added. 

232. — Since traces of Mn may be precipitated with AmHO, it is 
as well to test a portion of this residue for Mn by fusion on platinum 
foil with Na 2 C0 3 and KN0 3 , when a green mass will be formed. 

233. — Since HNO s has been added in an earlier part of the 
analysis, the iron at this stage will be in the ferric state. A small 
quantity of the original substance dissolved in HC1 should be tested 
for ferrous and ferric iron by paragraphs 165 and 171. 

234. — Commercial KHO and NaHO frequently contain AL These 
reagents should be tested by acidulating and adding AmHO. 

235. — Potassium may also be detected at this stage by adding a 
small quantity of strong platinum chloride or sodium picrate solution 
and stirring with a glass rod ; a yellow crystalline precipitate will be 
formed in both cases if K is present (188, 188a). 

F 2 



68 PRACTICAL AGRICULTURAL CHEMISTRY [236 

236.-TABLE II. FOR THE 

Test for ammonium by heating the original solid with KHO solution, 
original solution (229) if not already acid add HC1 in excess. Add a few 
ignite over the Bunsen flame (230). Treat with a little strong HC1, warm, 



Residue is 
SiO, 

This resi- 
due should 
be quite 
white 



The filtrate may contain Al, 
Add a few drops of this solution to some ammonium- 
are present ; if not, phosphates are absent. 

To the rest of the solution add Am CI in moderate quantity 
phate is present, examine this precipitate by Table III. ; if 
examined as below. 



Precipitate may contain Fe 2 (HO) 6 , Al 2 (HO) 8 (232) 
If the precipitate is quite white, aluminium only 
will be present ; if coloured, iron will probably be present. 
Dissolve the residue in hot dilute HC1, add pure KHO or 
NaHO in excess, then add more KHO so as to have con- 
siderable excess. Warm and filter 



Residue will be Fe 2 (OH) 8 
Dissolve in hot dilute 
HC1 and add KCNS, a 
blood-red coloration shows 
Presence of Fe (233) 



Filtrate will contain 
Al 2 (OH) 6 dissolved in ex- 
cess of KHO 

Add strong HC1 until 
the solution is distinctly acid, 
then add Am HO very 
cautiously until the solution 
is faintly alkaline. A white 
gelatinous precipitate shows 

Presence of Al (234) 



236] WET SEPARATION OF METALS 69 

SEPARATION OF THE METALS 

ammonia gas will be evolved which turns turmeric-paper brown. To the 
drops of strong HN0 3 , evaporate to dryness in a porcelain dish, and very gently 
add water and filter. 



Fe, Mn, Ca, Mg, K, Na 

molybdate solution and warm ; if a yellow precipitate forms, phosphates 

(231), heat to boiling, and then add AmHO in excess ; filter. If a phos- 
absent, examine the precipitate as below. In any case the filtrate must be 



Filtrate may contain Mn, Ca, Mg, K, Na 

Add Am 2 S until the solution has a distinct yellow tinge. Warm and filter 



Buff precipi- 
tate will 
beMnS 
Confirm by 
heating on 
platinum foil 
with Na 2 CO s 
andKN0 3 ; a 
green mass 
shows 
Presence 
of Mn 



Filtrate may contain Ca, Mg, K, Na 
Add ammonium oxalate (Am 2 C 2 4 ) solution in fair 
excess, filter 



White 

precipit ite 

will be 

CaC 2 0, 

showing" 

presence 

ofCa 



Filtrate may contain Mg, K, Na 
Evaporate the filtrate to dryness in a 
porcelain dish, scrape out the residue on to a 
piece of platinum foil, ignite until all fumes 
cease to be evolved. Boil the foil in a very 
small quantity of water containing a few 
drops of HC1. Divide into two portions. 



Examination 
for Mg 
Add AmCl, 
Am HOin excess, 
and Na 2 HP0 4 
and shake well ; 
a white crystal- 
line precipitate 
shows 
Presence of Mg 



Examination for K 

and Na 
Take up a little of the 
solution on the loop of 
platinum wire and hold in 
the Bunsen flame. 

(1) A pale violet flame 
shows 

Presence of K and 
absence of Na 

(2) A bright yellbw 
flame shows presence of 
Na. Examine this flame 
through the indigo prism 
or cobalt glass ; a crimson 
flame shows 

Presence of K (235) 



70 PRACTICAL AGRICULTURAL CHEMISTRY [237~239a 



237. TABLE III.-FOR THE EXAMINATION OF 
THE PHOSPHATE PRECIPITATE 

The AmHO precipitate may contain FeP0 4) AlP0 4 , 
Ca 3 P 2 8 , MgNH 4 P 2 8 

Dissolve the precipitate in hot dilute HC1. To the solution add 
Am^COjj solution, drop by drop, until the precipitate first formed re- 
dissolves with difficulty (238). Add a fair quantity of a mixture of 
acetic acid and ammonium acetate solution, and then add FeCl 3 until 
the liquid becomes reddish ; warm and filter. 



Filtrate may contain 
Ca and Mg- 

Add AmHO in excess, filter 
(239) and add Am. 2 C 2 4 solu- 
tion ; warm and filter 



Precipi- 
tate will 
be CaC,0 4 

showing 

presence 

of Ca 



Filtrate may 
contain Mg- 
Add Na 2 HP0 4 
solution and 

shake ; a white 
crystalline precipi- 
tate shows 
Presence of Mg 



Precipitate will contain FeP0 4 
and possibly A1P0 4 

Heat precipitate with K.HO solu- 
tion ; filter 



Filtrate may 
contain A1P0 4 
dissolved in 
KHO 

Add HC1 in ex- 
cess, then AmHO 
in very slight 
excess ; a white 
gelatinous precipi- 
tate shows 
Presence of Al 



Precipitate will 
contain FeP0 4 , 

which reject, since 
iron will always 
be found at this 
stage owing to 
FeCL; having been 
added (239a). 



EXPLANATION OF THE PHOSPHATE TABLE 

238. — The separation of the above phosphates depends on the 
following facts : — 

The phosphates of iron and aluminium are insoluble in acetic acid, 
whereas those of calcium and magnesium are soluble. Hence the 
HO solution of the phosphates is altered by the addition of HA and 
AmA into an acetic acid solution, when A1P0 4 and FeP0 4 precipitate. 
The FeCL, is added for the purpose of precipitating the remainder (if 
any) of the phosphoric acid as FeP0 4 , and so leaves the Ca and Mg as 
acetates, which are then tested for by the usual reagents. 

239. — It is usually necessary to filter at this stage, since a little 
iron may be left in the solution. The AmOH would then cause a 
brown precipitate, which is neglected. 

239a. — This precipitate of FeP0 4 is neglected here, since FeCL, has 
been added. Iron should be tested for in the original solution by 
tests (165 and 171). It should be noted that the metals Ca and Mg 



240-245] EXAMINATION FOR ACID-RADICALS 



may also be present ' not as phosphate,' and of course will be found in 
Table II. 

The four metals, Fe, Al, Ca, and Mg, should be returned 'as 
phosphate ' or • not as phosphate,' exactly as they are found. 



TABLE IV.— PRELIMINARY EXAMINATION 
FOR ACID-RADICALS 

In the following tests either the solid or a strong - solution may be 
used : — 



Test 


Observation 


Inference 


240. Expt. I.— Treat 
a little of the substance 
with dilute HC1 and 
heat gently 


1. A colourless gas is 
given off which turns 
lime-water milky 

2. Red fumes 


CO.j from a 
carbonate 

N.,0 3 from a 
nitrite 


241. Expt. II.— Heat 
a little of the substance 
with strong H 2 S0 4 

242. — Confirm by heat- 
ing another portion with 
Mn0 2 , free from chloride, 
and strong sulphuric acid 

243. — Confirm by drop- 
ping a few Cu turnings into 
the liquid and heat again 


1. A gas with a pun- 
gent acid smell is given 
off which fumes in the 
air and turns a drop of 
silver nitrate solution 
milky 

A pale yellow gas is given 
off with choking smell, and 
which bleaches test-papers 

2. An acid gas is 
given off, occasionally 
reddish in colour 

Red fumes given off 


HC1 from a 
chloride 

CI from a 
chloride 

Presence of 
a nitrate 

NO from a 
nitrate 



TABLE V.— FURTHER EXAMINATION FOR ACID- 
RADICALS 

244. Sulphate.— Boil a little of the original substance 
with dilute HC1, filter, and add barium chloride solution ; 
a white precipitate of BaS0 4 shows presence of a sulphate. 

245. Chloride.— Boil a portion of the original sub- 
stance with dilute fiN0 3 , filter, and add AgN0 3 solution; 
a white precipitate denotes presence of a chloride. 



72 PRACTICAL AGRICULTURAL CHEMISTRY L'246-251 

246. Nitrite. — Boil with water, filter, and test with Kl 
solution, starch, and HA (197) ; a blue coloration will 
appear. 

247. Nitrate. — Boil the original substance with water ; 
filter, cool under the tap, and add very cautiously an equal 
bulk of strong sulphuric acid ; cool in water. When quite 
cold add slowly down the sides of the tube a little of a cold 
solution of FeS0 4 . Where the liquids come in contact a 
brown ring will be formed. 

248. Phosphate. — A phosphate, if present, will 
usually have been detected in Table II. (236). It is readily 
detected by boiling the original substance with dilute 
HNO3 and then adding a few drops of this solution to 
ammonium molybdate solution ; a yellow precipitate forms 
on warming. 

249. Silicate. — A silicate will usually be found in 
Table II. (236). It may be readily detected if a little of the 
finely powdered substance is fused with Na 2 C0 3 on plati- 
num foil, and then treated with HC1. On evaporating to 
dryness the Si0 2 will be rendered insoluble, so that on 
treating with HC1 and water the Si0 2 will be left as a white 
powder (208). 

ANALYSIS OF SUBSTANCES INSOLUBLE IN 
WATER AND ACIDS 

250. The insoluble substances usually associated with 
agricultural products are silica, silicates, and phosphates. 

251. Mix the finely powdered substance with six times 
its weight of fusion mixture (268). Place in a porcelain 
or, preferably, a platinum crucible. Heat gently at first, 
then strongly over the blowpipe. Continue the heating until 
all effervescence ceases. Allow to cool and place the 
crucible and contents in a beaker, and gently heat with 
dilute HC1 until the residue is all dissolved, or only gelati- 



252-258] INSOLUBLE SUBSTANCES J I 

nous silica is left. Transfer to a porcelain dish, cautiously 
evaporate to dryness, and ignite gently. Now cover with 
strong HC1, warm, and dilute with water. The silica will be 
left in an insoluble form, and may be filtered off. 

252. The solution is then examined for metals by 
Tables II. and III. (236 and 237), and for acid-radicals by 
Tables IV. and V. (240-249). 

253. Since HC1 has been added, a portion of the original 
powder should be boiled with sodium carbonate solution, 
the solution filtered, and then tested for chloride by adding 
dilute HNO3 m excess, and afterwards AgN0 3 solution, 
when a white precipitate of silver chloride will form if 
chloride is present. 

254. Nitrates are not found in insoluble bodies, as all 
nitrates are soluble in water. 

255. Since Na and K cannot be tested for in the solu- 
tion obtained after fusion, owing to the fusion mixture 
consisting of Na 2 C0 3 and K 2 C0 3 , it is necessary to use a 
separate portion for the detection of these metals. 

256. The most convenient method is that of Lawrence 
Smith. Mix the powdered substance with six times its 
weight of a mixture of one part pure solid AmCl and six parts 
pure precipitated CaC0 3 . Place in a crucible, and heat to 
redness for twenty minutes. Allow to cool, boil up with 
water, and filter. The filtrate will contain the alkalies 
together with excess of calcium hydroxide. Precipitate the 
calcium by adding AmHO, Am 2 C0 3 , and a few drops of 
Am 2 C 2 0, solution ; filter, evaporate to dryness, and 
ignite. 

257. Dissolve in a very small quantity of water ; test 
for sodium by holding a little of the solution in the Bunsen 
flame on a platinum wire, when the golden flame coloration 
will be seen if Na is present. 

258. Potassium may be detected by viewing the flame 
through an indigo prism or cobalt glass, when the crimson 



74 PRACTICAL AGRICULTURAL CHEMISTRY [259 

coloration will be seen if K is present. Potassium may 
also be detected by platinum chloride (188) or sodium 
picrate (188a). 

259.— Example of Method of Entering the Results op 
an Analysis in the Note-book 

Examination of pale brown earthy substance 

Preliminary Examination for Metals 



Experiment 


Observation 


Inference 


I. Heated in an ig- 
nition-tube 


Little water given 
off; no charring 


H 2 present, or- 
ganic matter absent 


2. Heated on Pt wire 
in Bunsen flame after 
moistening with HC1 


Yellowish - red 
flame 


Trace Na ; Ca 
present 


3. Heated in borax 
bead 


No result 


Fe, Mn probably 
absent 



Wet Examination 

Boiled substance with water ; did not dissolve. Treated with 
dilute HC1, all dissolved. Evaporated to dryness, moistened with 
HC1, added water, filtered off trace of SiO i} and tested filtrate for 
metals. 

Heated a few drops of solution with ammonium molybdate, obtained 
no precipitate ; hence phosphates were absent. To bulk of solution 
added AmCl and AmHO. 



No pre- 
cipitate ; 

.*. Fe 
and Al 

absent 



To solution added Am 2 C 2 o filt ered 



White pre- 
cipitate 
Ca present 



Evaporated to dryness, ignited, dissolved 
residue in dilute HC1, divided into two 
portions 



1. Added AmHO 

and Na,HP0 4 , 

white crystalline 

precipitate 

Mg present 



2. Tested on Pt wire 
in Bunsen flame, faint 
yellow flame, no crimson 
colour through prism 
,\ Trace Na present 



259] METHOD OF ENTERING RESULTS 

Preliminary Examination for Acid-radicals 



75 



I. Heated with 


Gas given off with 


Presence of car- 


dilute HC1 


effervescence, which 
turned lime - water 


bonate 




milky ; no red fumes 


Nitrite absent 




evolved 




2. Heated with 


Ditto 


Probable absence 


strong H 2 S0 4 




of chloride and 
nitrate 



Wet Examination for Acid-radicals 



1. Heated substance with 
dilute HC1, filtered, added 
BaCl 2 and warmed 

2. Heated substance with 
dilute HNO : „ filtered, and 
added AgN0 3 

3. Heated substance with 
water, filtered, added strong 
HJ30 4 , cooled, and then 
added cold FeS0 4 solution 



Faint white 
precipitate 

Faint milki- 
ness 



No brown ring 



Trace of sul- 
phate 



Trace 

chloride 



of 



Nitrate absent 



Phosphate was shown to be absent in the wet examination for the 
metals. 

Found : Ca, Mg-, water, carbonate, traces of sodium, 
chloride, silicate, and sulphate 



76 PRACTICAL AGRICULTURAL CHEMISTRY [260 



SECTION V 

APPARATUS, CHEMICALS AND REAGENTS 
List of Bench Apparatus for each Student 

200. A list of the apparatus which should be kept in 
each bench-locker is given here. The Bunsen burner, with 
its indiarubber tube, may be left attached to the gas-tap on 
the bench. All the other apparatus should be locked up 
in the bench-locker when not in use. 

1 Bunsen burner about 5 \ inches high, with |-inch 
tube, and means of closing the air-holes. 

1 Rose-top to fit burner. 

1 Piece of black indiarubber tubing, -^ inch internal 
diameter and 16 inches long, to supply gas to the burner. 

1 Test-tube stand with twelve holes, two of which are at 
least an inch across. 

1 Test-tube brush. 

1 2 Test-tubes, 5 inches long by f inch diameter. 

2 Boiling-tubes, 6 inches long by 1 inch diameter. 

2 Round glass plates, ground on one side, 3 inches across. 
2 Berlin porcelain evaporating-dishes with spouts, glazed 
inside and out, and 3 inches in diameter. 

2 Watch-glasses, 2 inches across. 
Conical flask, 4 oz. capacity. 

1 Wedgwood mortar, 4 inches across, and pestle with 
wooden handle. 

1 Iron tripod stand, 7 inches high, with round top 
4 inches across. 

1 Piece of coarse iron wire gauze, 5 inches square. 

3 Glass funnels, two of them 2J inches across, one 
2 inches across. 



261] APPARATUS FOR GENERAL USE 



77 



3 Beakers, wide form of 2, 4, and 6 oz. capacity. 

3 Glass rods, rounded at the ends, 7, 6, and 3 inches 
in length. 

1 Piece of platinum foil, 1 x i^ inch. 

2 Pieces of platinum wire, mounted (7). 
1 Black's blowpipe, japanned tin. 

1 Pipe-clay triangle, 2 inches along the side. 
1 Wash bottle, to be made from 18 oz. flask (10). 
1 Retort stand. Upright rod 17 inches, foot 6x3 inches, 
with three brass rings, the largest 3 inches across. 

1 Wooden filter-stand, 1 2 inches high, with two rings. 
1 Pair polished brass crucible tongs, 6 inches long. 
1 Small horn spatula, 3J inches long. 
1 Oval wicker draining basket, 10x8x4 inches. 
Cut filter-papers, 4^, 3 J, and 2| inches across. 
1 White porcelain tile, 4^ inches square. 

List of Special Aparatus for Sections I., II., and III. 

261. This apparatus need not be supplied to each 
student, but several sets should be kept 

1 Nest of three or four small brass cork-borers. 

1 Triangular file. 

1 Thin round file. 
Several lengths and pieces of hard glass-tubing, about 
£ inch internal diameter. 

1 Gross ignition-tubes, 3 inches long, J inch across. 

1 Gross corks, as free as possible from holes or cracks, 
varying from § to j inch across. 

1 Small metal clamp in a boss .fitting the retort stand 

(% 15)- 

i Stoppered bell-jar, 30 oz. capacity. 

4 Glass cylinders on feet with ground edge at top, 
8 inches high, if inch across. 

4 Similar cylinders, 6 inches high, i\ inch across. 



78 PRACTICAL AGRICULTURAL CHEMISTRY [262 

i Round brown stoneware trough, 12 inches across, 
5 inches deep. 

1 Metal deflagrating-spoon. 

2 Two-necked Woulffe's bottles, 8 oz. capacity. 

1 Tubulated retort, 6 oz. capacity. 

2 Thistle funnels, 8 inches long. 

4 Pieces of black indiarubber tubing, ^ inch in internal 
diameter, 1^ inch long. 
Wooden spills. 
Wax tapers. 
1 Pair of scissors. 
1 Brass wire sieve, 20 meshes to the inch. 

List of Apparatus for General Use in Analysis 

262: The following apparatus should be kept in the 
laboratory for the general use of students. One set will 
suffice for about twelve students. 

1 Spirit-lamp, 4 oz. capacity, with earthenware wick- 
holder and ground glass cap. 

If gas is not available a set of these lamps will be required in place 
of Bunsen burners (260). 

4 Berlin porcelain crucibles, 1 \ inch across, with covers. 

1 Iron mortar, 8 inches across, with pestle. 

1 Fletcher's foot-bellows and blowpipe- table covered 
with sheet zinc or lead. 

1 Fletcher's blowpipe with central blast and 2 taps. 

1 Indigo prism, stoppered, nearly filled with solution of 
indigo in strong sulphuric acid. The indigo solution is 
made by mixing commercial sulphindigotic acid with ten 
times its measure of strong sulphuric acid, leaving to settle 
for several days and decanting into the prism. 

N.B. — Cobalt-blue glass may be substituted for the 
above. 

1 Agate mortar, 3 inches across, and pestle. 

1 Copper water-bath, with several openings (fig. 11). 
When in use it should be two-thirds filled with water, and 



263] 



CHEMICALS AND REAGENTS 



79 



more water added from time to time to make up for evapo- 
ration, or preferably the bath is fitted with a constant level 
water-supply. 

i steam- oven (fig. 14) made of copper. The water 
should two-thirds fill the oven, and should be kept just 
below boiling. The loss by evaporation should be made 
good from time to time, if not fitted as described above. 
CHEMICALS AND REAGENTS 

263. In the following lists will be found the reagents 
and test substances required in the course. In the first 
column stands the name ; in the second the chemical 
formula of the substance. The subsequent columns give 
directions for their preparation for laboratory use. 

264.— Reagents required for each Bench 



Name 



Formula 



Weight of solid 

in grams to be 

dissolved in one 

Winchester of 

water 

(2,500 c.c.) 




Sulphuric acid .... 
Hydrochloric acid . . 

Nitric acid 

Acetic acid 

Ammonium chloride . . 
Ammonium hydrate . . 
Ammonium sulphide . . 
Ammonium carbonate 

{note 1) 

Ammonium oxalate . . 
Potassium hydrate . . 
Potassium ferrocyanide . 
Potassium ferricyanide . 
Sodium phosphate 
Sodium carbonate 
Calcium sulphate . 

Barium chloride . 
Sodium carbonate 

Borax 

Potassium chlorate 
Test-papers . . . 



H 2 S0 4 . . . 
HC1 . . . . 
HNO3 .... 
HC 2 H 3 2 or HA 
NH 4 C1 . . . 
NH 4 HO . . 
(NH 4 ) 2 S . . 
(NH 4 ) 2 C0 3 . 

(NH 4 ) 2 C 2 4 .H 2 0, 
KHO . . . 
K 4 Fe(CN) 6 . 3 H 2 0, 
K 3 Fe(CNJ 6 (»*/*2) 
Na2HP0 4 .i2H 2 
Na 2 C0 3 .ioH 2 . 
CaS0 4 . . . . 

BaCl 2 .2H 2 . . 
Na 2 C0 3 • • . 
Na2B 4 7 .ioH 2 . 
KCIO5 . . . . 



300 



400 

100 
300 
200 
200 
200 
600 
Saturated so- 
lution 
200 
Solid 
Solid 
Solid 
Blue and red lit- 
mus and yellow 
turmeric-papers 
in small strips 



3m 
3m 
1 m 
8w 
3m 
1 m 
6 w 

24 w 

8 w 

12 w 

12 w 

12 W 

4W 



80 PRACTICAL AGRICULTURAL CHEMISTRY [265 



Note i. — The solid (NH,) z C0 M is dissolved in cold water, but in 
diluting, one-fourth of the * Winchester' must be filled with 3trong 
NH 4 HO. 

Note 2.— This reagent undergoes decomposition by exposure to 
light, and must not be kept near a window : it is better to dissolve a 
fragment of the solid each time it is required. 

265.— Chemicals required for Sections I. and II. 

With the exception of the bench reagents the whole of the sub- 
stances required for these sections are enumerated below : — 



Name 


Formula 


Remarks 


Alum ..... 


A1K(S0 4 ) 2 .I2H. 2 


Solid 


Ammonium chloride . 


NH 4 C1 . 


Solid 


Calcium chloride . 


CaCl 2 


Solid and solution 


Manganese sulphate . 


MnS0 4 . 


Solid 


Potassium nitrate 


KNO, 


Solid 


| Marble .... 


CaCO, 


In lumps 


Manganese dioxide 


Mn0 2 


Solid 


Wood charcoal . . 


C . 


In pieces the size 
of a hazel-nut 


Lime-water • • . 


Ca(OH) 2 . 


Saturated solution 


Sulphur .... 


S . 


Pieces of roll sul- 
phur the size of 
a pea 


Phosphorus . . 


P . 


Kept under water 


Granulated zinc . . 


Zn . . . 


Not necessarily 


Hydrochloric acid 


i;ci . 


pure 
Strong 


Sulphuric acid 


H v S0 4 . 


Strong 


Nitric acid .... 


HN03 . 


Strong 


Potassium iodide. . 


KI . 


Solid 


Starch powder . . . 





_ 


Slaked lime 


Ca(OH) 2 . 


Solid 


Ammonia .... 


NH 4 (OH) . 


Strong solution 




AgNO s . 


Solution 


Methylated spirit 


C 2 H 6 . . 


Free from coal-oil 


Mercuric chloride . . 


HgCl 2 . . 


Solid 


Potassium hydrate 


KHO 


Solid 


Nessler's Solution {note 1) . 


— 


— 



Note 1. — Dissolve 33 grams of KI and 13 grams of HgCl 2 in 
800 c.c. of water, add strong HgCl 2 solution antil a faint permanent 
precipitate is formed, then add 160 grams of solid KHO. Allow to 
cool and make up to one litre with water. Use the clow supernatant 
liquid. 



266.— Substances 


used for Section 


III. 


Name 


Formula 


Remarks 


Loam ..... 





Air-dried 


Lime-water . 


Ca(OH) 2 . 


Saturated 

solution 


Clay 


— 


Air-dried 


Marble ..... 


CaC0 3 . 


Ground fine 


Peat soil .... 


— 


Air-dried 


Quicklime . 


CaO 


Freshly burned 


Litmus solution 


— 


— 


Ferrous sulphate . 


FeS0 4 .7H 2 . 


Solid 




— 


Fresh 


Gypsum .... 


CaS0 4 .2H a O . 


Solid 


Charcoal .... 


C 


Powder 


Kainit 


K 1 Mg(S0 4 ) r 6H 1 


Commercial 


Coprolite powder . 


— 


— 


Basic slag .... 


— 


— 




CaH 4 (P0 4 ) 2 . 


Commercial 


Citrate of ammonium (note i) . 


(NH 4 ) S CI . 


Solution 




(NH 4 ) 2 S0 4 . 


Commercial 


Nitrate of soda 


NaNO s . 


Commercial 


Shoddy 


— 


— 


Soda-lime .... 


— 


Granulated 


Indigo carmine 


— 


Solution 


Sulphuric acid 


H 2 S0 4 . 


Strong 


Peruvian guano 


— 


— 


Ammonium molybdate (note 2) 


NH 4 HMo0 4 . 


Solution 


Ferric chloride 


FeCl 3 . 


Solution(i:ioo) 


Potassium sulphocyanide 


KC.NS . 


Solution(i:ioo) 


Bone-meal .... 


— 


— 


Linseed cake 


— 


Ground fine 


Cotton cake, decorticated 


— 


Ground fine 


Cotton cake, undecorticated . 


— 


Ground fine 


Glycerine .... 


C 3 H s (OH) 3 . 


— 


Ether 


C 4 H l0 O . . 


— 




— 


— 


Solution of iodine in potassium 






iodide 


I and KI . 


Dilute solution 


Alcohol (methylated spirit) . 


C 2 H 8 . 


Free from coal- 
oil 


Hay . . . . 







Turnips .... 


— 


Provided fresh 
when wanted 


Cane sugar .... 


— 


Crystallised 


Glucose .... 


— 


— 


Carbolic acid 


— 


80 % solution 


Formalin .... 


CH 2 . 


40 % solution 


Flour 


— 


Wheaten 


Milk 


— 


Fresh 


Butter 


— 


Fresh 


Cheese 


— 


Fresh 



82 PRACTICAL AGRICULTURAL CHEMISTRY [267 

Note |, — Made by rendering a strong solution of citric acid dis- 
tinctly alkaline with ammonia. 

Note 2.— Measure ioo c.c. water into a large flask, add 50 grams 
molybdic acid or 70 grams of ammonium molybdate, then 100 c.c. of 
strong ammonia ; stir until dissolved. Pour the solution into 720 c.c 
cold nitric acid, sp. g. 1 "20, stirring whilst adding. 

Note 3.— Best kept as two solutions, A and B : A contains about 
35 grams of copper sulphate dissolved in 500 c.c. of water, B contains 
173 grams of Rochelle salt (sodium potassium tartrate) and 160 grams' 
of potassium hydrate in 500 c.c. of water. For immediate use equal 
quantities of each are mixed. 



267.— Reagents for General Use for the Detection 
of Metals 



Name 


Formula 


Proportion by weight of 
solid to water 


Sulphuric acid 


H 2 S0 4 . 


Strong pure 


Hydrochloric acid . 


HC1 . 


Strong pure 


Nitric acid 


HN0 3 . 


Strong pure 


Platinum chloride . 


PtCl 4 . 


1 : 3° 


Methylated spirit . 


C 2 H u O . . 


Strong 


Slaked lime . 


Ca(HO) 2 


Solid 


Potassium sulphocyanide. 


KCNS . 


1 : 100 


Potassium nitrate . 


KNO s . 


Solid 


Silver nitrate . 


AgN0 3 


1 : 100 


Magnesium sulphate 


MgS0 4 .7H 2 


1 : 12 



208] REAGENTS FOR THE ACID-RADICALS 



83 



J. — Reagents for General Use for the Detection of 
Acid-radicals 







Proportion by 


Name 


Formula 


weight of solid to 
water 


Lime-water . . . 


Ca(OH) 2 . 


Saturated 


Ferric chloride {note 1) 


FeCL, . . . 


1 : 24 


*Ferrous sulphate 


FeS0 4 .7H,0 


Solid 


Potassium iodide 


KI . " . 


1 : 60 


*Starch .... 


— 


— 


Indigo carmine solution 


— 


— 


Manganese dioxide {note 2). 


MnO., . 


Solid 


Ether (methylated) . 


— 


— 


* Potassium nitrite 


KN0 2 . 


Solid 


Ammonium molybdate {n. 3) 


NH 4 HMo0 4 


— 


Microcosmic salt 


NaNH 4 HP0 4 .4H,0 


Solid 


Wax or paraffin . 


— 


Solid 


Distilled water . 


H 2 . 


— 


Pure sodium hydrate . 


NaHO 


1 : 10 


Fusion mixture {note 4) 


K 2 C0 3 + Na 2 C0 3 . 


— 


Solution of sodium acetate in 






dilute acetic acid {note 5). 


NaA and HA . 


— 


Calcium carbonate, pure 


CaC0 3 . 


Powder 


Ammonium chloride, pure . 


NH 4 C1 


Powder 


*Potassium ferricyanide 


K 3 Fe(CN) 6 . 


Solid 



* These solids do not keep in solution. 

Note 1. — The solution should not contain any free acid. To remove 
this AmHO is added until the further addition of a single drop gives 
a reddish-brown precipitate. Filter off this precipitate, and the solu- 
tion is ready for use. 

Note 2. — Should be kept in fine powder ; it must not evolve CI or 
C0 2 when warmed with strong H 2 S0 4 . 

Note 3. — See note 2, paragraph 266. 

N te 4.— Dry finely powdered Na 2 CO a and K 2 CO s are mixed in 
proportions of 53 : 69 by weight and kept in a stoppered bottle. 

Mote 5.— Dissolve 20 grams NaA in 60 c.c. of distilled water and 
add to the solution 40 c.c.of strong HA. 



84 PRACTICAL AGRICULTURAL CHEMISTRY [269-270 



269.— Solutions 


for the Reactions of the Metal3 


Name 


Formula 


Weight of solid 

in grams to be 

dissolved in one 

Winchester of 

water 


Proportion 

by weight 

of solid to 

water 


Potassium chloride . 


KC1 . 


100 


1:25 


Ammonium chloride . 


NH 4 C1 


200 


1 : 12 


Sodium chloride 


NaCl . 


So 


1:50 


Magnesium sulphate . 


MgS0 4 .7H 2 O . 


So 


i:5o 


Calcium chloride 


CaCl 2 .6H 2 


200 (in crystals) 


1 : 12 


Alum. 


A1K(S0 4 ) 2 . i2H 2 


200 


1 : 12 


Ferric chloride . 


FeCl, . . 


25 


1 : 100 


Ferrous sulphate 


FeS0 4 . 7 H 2 . 


25 


1 : 100 


Manganese sulphate . 


MnS0 4 


25 


1 : 100 



27a. —Solutions for the Reactions of the Acid-radicals 



Name 


Formula 


1 

Weight of solid 

in grams to be 

dissolved in one 

Winchester of 

water 


Proportion 

by weight 

of solid to 

water 


Sodium sulphate 
Sodium carbonate 
Potassium nitrite 
Potassium nitrate 
Sodium chloride 
Sodium phosphate 
Sodium silicate . 
Silica (white sand) . 


Na 2 S0 4 .ioH 2 . 
Na2C0 3 . 
KN0 2 

KN0 3 . . 
NaCl . 

Na2HP0 4 .i2H 2 
Na-jSiOs . 
Si0 2 . 


25 

100 
IOO 

50 

50 

IOO 


1 : 100 
Solid 
1:25 
1:25 

1:50 
1:50 
1:25 
Solid 



Note. — The above substances (269, 270) will also be required in 
the solid form for many of the tests. 



271-272] ATOMIC WEIGHTS OF ELEMENTS 



85 



271.— List of Chemical Elements, with their Symbols 
and Atomic Weights 

The words in brackets are the Latin names of the elements from 
which the symbols have been derived. 



Name 


Symbol 


Atomic 
Weight 


Name 


Symbol 


Atomic 
Weight 


Aluminium 


Al 


27 


Molybdenum . 


Mo 


96 


Antimony (stibium) . 


Sb 


120 


Nickel 


Ni 


59 


Arsenic 


As 


75 


Niobium . . 


Nb 


94 


Barium 






Ba 


i37'4 


Nitrogen . 


N 


M 


Beryllium 






Be 


9 


Osmium . . 


Os 


191 


Bismuth 






Bi 


208 


Oxygen . . . 


O 


16 


Boron 






B 


11 


Palladium 


Pd 


107 " 


Bromine 






Br 


80 


Phosphorus 


P 


3 1 


Cadmium 






Cd 


112-4 


Platinum . 


Pt 


*95 


Caesium 






Cs 


133 


Potassium (kalium) . 


K 


39 


Calcium 






Ca 


40 


Rhodium . 


kh 


103 


Carbon 






C 


12 


Rubidium . . . 


Rb 


85'5 


Cerium 






Ce 


140 


Ruthenium . 


Ku 


i' 2 


Chlorine 






CI 


35'5 


Selenion . . 


Se 


79 


Chromium 




Cr 


5 2 


Silicon 


Si 


28*4 


Cobalt 




Co 


59 


Silver (argentum) 


Ag 


108 


Copper (cuprurr 


) ! 


Cu 


63-5 


Sodium (natrium) 


Na 


23 


Didymium 




D 


142 


Strontium . 


br 


8?'5 


Erbium 




E 


166 


Sulphur . 


S 


32 


Fluorine . 




F 


19 


Tantalum . * 


Ta 


181 ". 


Gold (aura in) 




Au 


197 


Tellurion . 


Te 


127*6 


Hydrogen 




H 


i'oi 


Thallium . . 


Tl 


204 


Indium 




In 


"3"4 


Thorinum . 


Th 


232-5 


Iodine 




I 


127 


Tin (stannum) . 


Sn 


119 


Iridium 




Ir 


J 93 


Titanium . 


Ti 


48 


Iron (ferrum) 




Fe 


56 


Tung>ten (wolfra-\ 
mium) . . / 


W 


I8| 


Lanthanum 




la 


138 




Lead (plumbum 


) ! 


Pb 


207 


Uranium . 


U 


238*5 


Lithium . 




L 


7 


Vanadium . . . 


V 


5i 


Magnesium 




Mg 


24 "4 


Yttrium . 


Y 


89 


Manganese 




Mn 


55 


Zinc .... 


Zn 


65-4 , 


Mercury (hydrar- \ 
gyrum) . . / 


Hg 


200 


Zirconium . 


Zr 


9i 



272.— Thermometric Scales 

There are two different thermometric scales in use in this country, 
the Centigrade and Fahrenheit ; the former of these is rapidly becom- 
ing universal for scientific purposes. The two scales are mutually 
convertible by the following formake, in which F.° represents a tem- 
perature on the Fahrenheit scale, C.° a temperature on the Centigrade 
scale : — 

I (F.° - 32) = C.° 

I C.° + 32 - F.° 

The temperatures occasionally referred to in this book are given on 
the Centigrade scale. 

G3 



8(5 PRACTICAL AGRICULTURAL CHEMISTRY [273-274 



273. — English Weights and Measures 

apothecaries' weight avoirdupois weight 



lb. oz. drnis. scruples grains 

1 = 12 = 96 = 288 = 5760 

1 = 8 = .24 = 480 

I = 3 = 60 

1 = 20 



lb. 



07.. 


drms. 


grains 


l6 


= 256 = 


7000 


I 


* 16 = 


437'5 




z = 


27*341 



gallon 



IMPERIAL MEASURE 



pints 




fluid oz. 




fluid drms. 


8 


s= 


160 


 


1280 


1 


= 


20 


■i 


160 






1 


SB 


8 



1 gallon 

1 fluid ounce = V5 pint 

x gallon 

z fluid ounce 



70,000 grains of water at i6*7°C 

437 ' 5 lUl I. " 

277 280 cubic inches 
i"733 m 



274.— Metric Weights and Measures 



MEA 


SURES OF LEN( 


;th 


ENGLISH 




metre 


inches 


mile 


furlong 


Millimetre = 


o'ooi = 


o*o3937 = 






Centimetre = 


o'oi = 


0*39371 = 




t 


Decimetre = 


o'i = 


3-93708 = 


# 




Metre = 
Decametre = 


x*o = 
xo'o = 


39'37079 = 
393-70790 = 


• 


• 


Hectometre = 


1000 = 


3937'o79oo = 


# 


t 


Kilometre = 
Myriometre = 


IOO^'O *= 


3937o 79000 = 


. 


4 


lOOCO'O = 


393707'9oo-.o = 


6 






z inch = '0254 metre. 








z foot = '3048 


»» 





inches 



. 


. 


0*03937 


• 


• 


C3937 z 


• 


• 


3'937i 


• 


3 


3'37i 


10 


a 


9*7 


109 


T 


1 


213 


4 


io'a 


156 





6 



MEASURES OF CAPACITY 
I litre = 1 cubic decimetre 



1 Millilitre, or I 
I Cubic centimetre (c.c.) J 

Centilitre = 

Decilitre as 

Litre c= 

Decalitre = 

Hectolitre = 

Kilolitre s* 

Myiiolitm = 



litre 



0001 



001 

o'i 

i*o 

io'o 

zoo'o 

iooo'o 

ioooo'o 

f cubic inch = 
f cubic foot = 
1 gallon m 



cubic inches 
m 0*06103 

= 0*61027 

= 6"zo27 

= 61*027 

= 610*27 
a= 6102 '7 
= 6 1027 'o 
= 610270*0 
0*01639 litre. 
2 8*3 T 53i litres. 
4*S4336 „ 



pints 

0*00176 

0*01761 

0*17608 

1*76077 

1760773 

176*07734 

I 76o-7734i 

17607*73414 



274] 



DECIMAL WEIGHTS 



87 



MEASURES OF WEIGHT 



gi am = the weight of i cubic centimetre (c.c.) of water at 4 C. 





grammes 




grains 


Avoirdupois 


Milligram 


= o'ooi 


-- 


0*01543 




Centigram 


= o'ot 


= 


0-15432 




Decigram 


= O'l 


= 


i*54323 




Gram 


= I'O 


= 


I5'43235 


lb. oz. drms. 


Decagram 


= 100 


= 


154*32340 


= 00 565 


Hectogram 


= ioo'o 


= 


154 J*23488 


= 03 8-5 


Kilogram 


= iooo"o 


— 


- 15432*34880 


= 235 


Myriogram 


= IOOOO'O 


= 


i54323'488oo 


= 22 I 9 




1 grain 


- 


0*0649 gram. 






x oz. (Troy) 


- 


31-1035 giaini. 





1 lb. (Avoirdupois) = 453'5y3 



INDEX 



Acidification of milk, 49 
Acidity of compound manures, 38 
Acid-radicals, examination for, 71 
Acids and alkalies, 12 

— action of lime on, 29 

— action of milk on, 49 

— reactions for, 61 
Air, action on lime, 29 

— carbonic acid in, 19 

— experiments on, 19 

— water in, 19 
Albuminoids in cheese, 52 

— in grass, 44 

— in milk, 49 

— in oil-cakes, 42 

— in turnip juice, 47 
Alkalies and acids, 12 

— in grass, 45 

— in insoluble substances, 73 
Aluminium, tests for, 55 
Ammoniacal nitrogen, test for, 34, 40 
Ammonia in guano, 36 

— in water, 25 

— preparation of, 18 

— properties of, 18 

— sulphate of, 37 

Ammonium citrate, action on phos- 
phate, 32 
action on reverted phosphate, 33 

— molybdate, preparation of, 82 

— tests for, 60 

Analysis of insoluble substances, 72 

— qualitative, 53 

tables for, 65 

Apparatus, cleaning of, 54 

— for each student, 76 

— for general use, 78 

— for Sections I., II., and III., jj 
Ash in grass, 45 

— in guano, 36 
Atmospheric burner, 1 
Atomic weights, 85 



Bath, steam, 8 

Bellows, foot, 3 

Bending glass tube and rod, 3 

Blowpipe, 2 

— mouth, 2 
— table, 3 

Bone, action of heat on, 37 

— action of acid on, 37 

— phosphate, 31 
Boracic acid in milk, 50 
Borax head, 12 

— in milk, 50 
Boring corks, 5 
Bunsen burner, 1 
Burner, atmospheric, 1 

— Bunsen, 1 

— fish-tail, 4 

Burning carbon in oxygen, 15 

— sulphur in oxygen, 14 
Butter, 51 

— curd in, 51 

— salt in, 52 

— water in, 51 



Cake, cotton, 44 

— linseed, 43 
Calcium, tests for, 58 
Cane sugar, 47 

inversion of, 47 

Carbohydrates in oil cake, 42 
Carbonate, tests for, 61 
Carbonates in water, 24 
Carbon dioxide, in air, 19 

preparation of, 16 

properties of, 17 

— organic, test for, 64 
Cereal foods, 48 
Cheese, 52 

— albuminoids in, 52 

— fat in, 52 
Chemical elements, 85 



INDEX 



8 9 



Chemicals and reagents, 79 

— for Sections I. and II., 80 
Chloride, tests for, 62 
Chlorine, organic, tests for, 64 
Chlorophyll, 45 

Clay in soils, 26 
Cleaning apparatus, 54 
Closed tubes, 4 
Cobalt-blue glass, 30 
Coloration of borax head, 12 

— of flame, 11 
Compound manures, 38 
Constituents of manures, 28 
Cork-borers, 5 

— boring, 5 
Cotton-cake, 44 
Cotton-wool in cotton-cake, 44 
Crystallisation, 8 

Curd in butter, 51 
Curdling of milk, 49 
Cutting glass tube and rod, 3 

Dairy produce, 49 
Decantation, 9 
Distillation of water, 22 
Distilled water, 22 
Drying precipitates, 10 

Elements, chemical, 85 
English weights and measures, 86 
Entry in note-book, 54, 74 
Evaporation, 7 
Explanation of phosphate table, 70 



Fat in cheese, 52 

— in milk, 49 

Feeding materials, experiments on, 41 
Fehling's solution, preparation of, 82 
Ferric salts, tests for, 57 
Ferrous salts, tests for, 56 
Fibre, woody, in oil-cakes, 43 
Filter paper, 9 

— folding, 9 
Filtration, 9 
Fish-tail burner, 4 
Fitting wash-bottle, 5 
Flame colorations, 11 
Flour, gluten in, 48 

— starch in, 48 
Folding filters, 9 
Foot-bellows, 3 
Formalin in milk, 5X 
Funnel, 9 

Fusion, 11 



Gas-lime, sulphur in, 30 

Glass rod, bending and cutting, 3 

— tube, bending and cutting, 3 
Gluten in flour, 48 

Grape sugar, 47 
Grass, 44 

— albuminoids in, 44 

— alkalies in, 45 

— ash in, 45 

— chlorophyll in, 45 

— phosphates in, 46 

— phosphoric acid in, 45 
Guano, ammonia in, 36 

— ash in, 36 

— soluble phosphates in, 36 
Gypsum, sulphur in, 30 

Hardness of water, 24 
Hay, 44 

— albuminoids in, 44 

— alkalies in, 45 

— ash in, 45 

— chlorophyll in, 45 

— phosphoric acid in, 45 
Heat, action on bones, 37 
Humus, nature of, 28 

— test for, 27 

Hydrogen, preparation of, 20 

— properties of, 21 

Ignition, ii 

— tubes, 4 
India-rubber corks, 5 
Indigo-prism, preparation of, 78 
use of, 11 

Insoluble phosphate, test for, 39 

— substances, analysis of, 72 
Inversion of cane sugar, 47 
Iron, action of lime on, 30 

— tests for, 56 



Juice in roots, 46 

Kainit, potash in, 31 

Lamp, spirit, 2 
Leguminous foods, 48 
Lime, action on acids, 29 

— action on air, 29 

— action on clay, 26 

— action on salts of iron, 30 

— action on superphosphate, 33 



90 



PRACTICAL AGRICULTURAL CHEMISTRY 



Lime manures, 28 

— slaking, 28 

— in soil, 27 

— solubility of, 29 

— tests for, 27 

— in water, 23 
Limestone soils, 27 
Linseed cake, 43 

adulteration of, 43 

mucilage in, 43 

starch in, 44 

Litmus paper, 12 
Loam, 26 



Magnesium, tests for, 59 
Manganese, tests for, 57 
Mangels, 46 
Manures, acidity in, 38 

— compound, 38 

— experiments on, 28 

— lime, 28 

— mixing, 35 

— nitrogenous, 33 

— phosphatic, 31 

— potash, 31 

— testing, 36 
Measures, 86 

Metals, preliminary examination for, 
65 

— reactions of, 55 

— separation of, 68 

— wet examination for, 67 
Metric weights and measures, 86 
Milk, 49 

— acidification of, 49 

— action of acids on, 49 
• — albuminoids in, 49 

— fat in, 49 

— preservation of preservatives in, 50 

— sugar in, 49 
Mineral phosphate, 31 
Mixing manures, 35 
Mounting platinum wire, 4 
Mouth blowpipe, 2 
Mucilage in linseed cake, 43 



Natural waters, 22 

Nessler's solution, preparation of, 80 

Nitrates, action on superphosphate, 

35 
Nitrate, test for, 62 
Nitric acid, action on phosphates, 32 
— nitrogen, 34, 40 
Nitrite, tests for, 61 



Nitrogen, ammoniacal, 34 

— ammoniacal, test for, 34, 40 

— in albuminoids, 41 

— in curd, 51 

— nitric, 34, 40 

— nitric, tests for, 34, 40 
Nitrogenous manures, 33 
Nitrogen, organic, 34 

— organic, test for, 34, 39, 64 

— preparation of, 15 

— properties of, 16 
Note-book, 54 

— entry of analysis, 74 

Notes on separation of metals, 67 



Oil-cakes, 41 

— albuminoids in, 42 

— carbohydrates in, 42 

— oil in. 41 

— sand in, 43 

— water in, 41 

— woody fibre in, 43 
Oil in oil-cakes, 41 
Organic carbon, test for, 64 

— chlorine, test for, 64 

— matter, test for, 27 

— nitrogen, tests for, 34, 39, 64 

— sulphur, test for, 65 
Oven, steam, 10 
Oxygen, preparation of, 13 

— properties of, 14 



Peat, 26 
Phosphate, bone, 31 

— mineral, 31 

Phosphates, action of ammonium 
citrate on, 32 

— action of dilute nitric acid on, 32 

— action of water on, 31 

— in grass, 46 

— insoluble, tests for, 38, 39 

— of lime, 31 

— soluble, tests for, 38 

— table, explanation of, 70 

— table for separation of, 70 

— tests for, 63 
Phosphatic manures, 31 
Phosphoric acid, 31 

in guano, 36 

Platinum wire mounting, 4 
Potash in kainit, 31 

— manures, 31 

— manures, tests for, 40 
Potassium, tests for, 60 



INDEX 



Precipitates, drying, 10 

— washing, 9 

Precipitation, 8 

Preliminary examination for acids, 71 

Preliminary examination for metals, 

65 
Process of solution, 67 
Pure water, 23 



Qualitative, analysis, 53 
tables for, 65 



Reactions for acid-radicals, 61 

— for metals, 55 
Reagents and chemicals, 79 

— for each bench, 79 

— for the acids, 83 

— for the metals, 82 
Results, statement of, 74 
Reversion of superphosphate, 32 
Reverted phosphate, 31 

action of ammonium citrate on, 

33 
Roots, 46 

Rose-top for bunsen, 2 
Rubber corks, 5 
Rules for working, 54 



Salt in butter, 52 

— in water, 24 

Sand and clay, separation of, 26 

— in oil-cakes, 43 

— in soil, 26 
Separation of metals, 68 

notes on, 67 

Shoddy, nitrogen in, 34 
Silicate, test for, 63 

Slag, action on sulphate of ammonia, 

35 • u u 

— action on superphosphate, 35 

— phosphate, 31 
Slaking lime, 28 
Sodium, tests for, 59 
Softening corks, 5 
Soil, limestone in, 27 
Soils, experiments on, 26 
Solids in water, 23 
Solubility, 6 

— of lime, 29 

— of the phosphates of lime, 31 
Soluble phosphates in guano, 36 
test for, 38 

Solution, 6 



Solution, chemical, 7 

— simple, 7 

Solutions for reactions of acids, 84 

of metals, 84 

Solvent, 6 
Spirit-lamp, 2 
Starch in flour, 48 

— in linseed cake, 44 
Steam bath, 8 
Steam oven, 10 
Sublimation, 11 
Substances for Section III., 81 
Sugar, cane, 47 

— grape, 47 

— in milk, 49 

— in roots, 46 

— inversion of, 47 
Sulphate, in water, 24 

— of ammonia, action of slag on, 35 

— of ammonia, testing, 37 

— of ammonia, volatility of, 37 

— test for, 61 
Sulphur in gas-lime, 30 

— in gypsum, 30 

— organic test for, 65 
Superphosphate, 31 

— action of lime on, 33 

— action of nitrates on, 35 

— reversion of, 32 
Swedes, 46 
Symbols, 85 



Table blowpipe, 3 

Tables for examination of acids, 71 

— for preliminary examination for 
metals, 65 

— for qualitative analysis, 65 

— for separation of metals, 68 

— for separation of phosphates, 70 
Test for carbon dioxide, 17 
Testing manures, 36 

Test papers, 12 
Thermometric scales, 85 
Thiocyanates, 37 
Tubes, closed, 4 

— ignition, 4 
Turmeric paper, 12 
Turnips, 46 

— juice in, 46 

— sugar in, 46 
Turnip-juice, albuminoids in, 47 



Volatility of sulphate of ammonia, 
37 



92 



PRACTICAL AGRICULTURAL CHEMISTRY 



Wash bottle, 5 
Washing precipitates, 9 

— precipitates, by decantation, 9 
by filtration, 10 

Water, action on phosphates, 31 

— ammonia in, 25 

— bath, 8 

— carbonates in, 24 

— distillation of, 22 

— experiments on. 22 

— hardness of, 24 

— in air, 19 



Water, in butter, 51 

— in oil-cakes, 41 

— lime in, 23 

— natural, 22 

— salt in, 24 

— solids in, 23 

— sulphates in, 24 
Weights, atomic, 85 
Weights and measures, 86 
Wet examination for metals, 67 
Woody fibre in oil-cakes, 43 
Working, rules for, 54 



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