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Full text of "Chemical methods for utilizing wood, including destructive distillation, recovery of trupentine, rosin, and pulp, and the preparation of alcohols and oxalic acid"

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http://www.archive.org/details/chemicalmethodsfOOveitrich 



Issued August 29, 1907. 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF CHEMISTRY— CIRCULAR NO. 36. 

H. W. WILEY, CHIEF OF Bureau. 



CHEMICAL METHODS FOR 
UTILIZING WOOD, 

INCLUDING DESTRUCTIVE DISTILLATION, RECOVERY OF 
TURPENTINE, ROSIN, AND i^ULP, AND THE PREPA- 
RATION OF ALCOHOLS AND OXALIC ACID. 



By 
F. P. VEITCH, 

Chief, Leather and Paper Laboratory. 



WASHINGTON : GOVERNMENT PRINTING OFFICE I I'jOT 

4208— No. 80—07 1 





1 



LEHER OF TRANSMITTAL 



U. S. Department of Agriculture, 

Bureau of Chemistry, 
WasUngton, D. C, May 10, 1907. 

Sir: The demand for information as to the nature and uses of 
the chemical compounds manufactured from wood and the processes 
and equipment used in their production has become so general that 
it is not possible to supply the desired data through the channels of 
correspondence. To meet this need, the accompanying manuscript 
has been prepared, and I recommend its publication as Circular 36 
of the Bureau of Chemistry. The requests received are largely with 
reference to the disposal of waste materials, and although the ques- 
tions involved are rather technical no effort has been made to produce 
an elaborate treatise on this subject, but rather to explain the proc- 
esses as simply as the subject-matter will permit. 

The utilization of wood wastes in chemical manufactures is attract- 
ing much attention at the present time, and the information here 
given is especially of interest in view of the temporarily depressing 
effect which the use of denatured alcohol will have on the demand 
for wood alcohol. 

While investigations made in this Bureau furnish much of the 
data given, acknowledgments are due to Hon. C. F. Wright, Mr. C. J. 
Root, Mr. Joseph Beimor, and Mr. J. J. Mallonee for general infor- 
mation, and to Messrs. Struthers-Wells & Co., Klar's Technologic der 
Holzverkohlung and Sjostedt in the Iron Age for January 28, 1904, for 
illustrations of apparatus. 
Respectfullv, 

H.W. Wiley. 

Chief Bureau of Chemistry. 
Hon. James Wilson, 

Secretary of Agriculture. 

[Cir. 36j 

(3) 



CONTENTS. 



Introduction 7 

Statistics of wood distillation 7 

Properties of wood affecting yield of prodiicls 9 

Specific gravity and weight 9 

Water content 10 

Composition 10 

Yield of distillation products from different woods 11 

Apparatus for destructive distillation 12 

Description of equipment 12 

Cost of plant 15 

Manufacturing processes 17 

General process of distillation 17 

Nature of the reactions in the retort 20 

Special features of the distillation of pine, fir, and spruce , 22 

Crude products of destructive distillation 23 

1. Noncondensable gases 24 

2. Charcoal 24 

3. Tar and oils 24 

Wood tar 24 

Wood oil 27 

Additional oils obtained from resinous woods 28 

Wood turpentine 29 

Pine oils 30 

Rosin spirits 31 

Rosin oils 31 

Tar oils : 31 

4. Aqueous distillate of crude pyroligneous acid 32 

General treatment for the separation of acetic acid and methyl alcohol . 32 

Acetic acid 33 

Aluminum acetate 35 

Chromium acetate 35 

Copper acetate 35 

Lead acetate 35 

Sodium acetate * 35 

Crude methyl alcohol and acetone 35 

Pure methyl alcohol. 37 

Acetone 37 

Recovery of certain wood products by treatment with chemicals 39 

Treatment with soda, soda ash, or volatile solvents 39 

Preparation of ethyl alcohol from sawdust 40 

Production of acetic acid and acetates by fusion with alkalies 40 

Manufacture of oxalic acid 41 

Suggestions for the development of these industries 43 

Yields 44 

Operating expenses 44 

Raw materials 46 

[Cir. 36] 

(5) 



ILLUSTRATIONS. 



Page. 

Fig. 1. Early form of kiln in which only charcoal is recovered 12 

2. Early form of kiln in which charcoal and tar are recovered 12 

3. Early kiln for recovery of alcohol and acid 13 

4. Swedish thermo-kettle 13 

5. Round retort with condenser 14 

6. A modem oven retort 14 

7. Types of condensers 15 

8. Wood car used in oven retort 17 

9. Charcoal cooler used with oven retort : 18 

10. Plan of a modem American destructive distillation plant 18 

11. Plan of a refining apparatus 19 

12. Plan of German type of fractional distillation plant 20 

13. Retorts used in distilling turpentine 22 

14. Diagram showing the processes and products of the destructive distilla- 

tion of wood -• 26 

15. Liming still 33 

16. Still for preparing acetic acid from acetate of lime, with detail of acetate 

pan 34 

[Cir. 36] 

(6) 



DESTRUCTIVE DISTILLATION PRODUCTS OF WOOD, IN- 
CLUDING THEIR NATURE AND USES AND OTHER 
CHEMICAL METHODS OF MANUFACTURE. 



INTRODUCTION. 

Each year there are milKons of cords of wood wasted in the forest 
and on the farm. This wood, because of its shape, size, or quality, 
is not suitable for the numerous mechanical uses for which wood is 
employed, and information regarding other means of disposing of 
this waste is of general interest. Aside from tanning and paper 
making, which are chemical industries that have been established for 
hundreds of years, there are other industrial uses, of more recent 
origin, which are of agricultural importance because they offer a 
means of utilizing these wastes of the sawmill and the forest. The 
more important of these are destructive distillation, recovery of tur- 
pentine, rosin, and paper pulp, preparation of alcohols, and manu- 
facture of acids. The growth of some of these industries has been 
rapid in recent years, and is not due alone to the demand for a 
method of utilizing the waste woods of lumbering operations, such as 
tops, sawdust, slabs, and timber too small to be profitably handled 
for lumber, but also to a steadily increasing demand for wood alcohol, 
acetates, acetone, turpentine, charcoal, etc., in other industries. In 
the past the demand for these products has been sufficient to encour- 
age the steady growth of the industries engaged in their production, 
and the values of the products have been well maintained, except in 
so far as the passage of the law permitting the tax-free use of denatured 
alcohol has affected the price of wood alcohol. 

STATISTICS OF WOOD DISTILLATION. 

Of the various processes employed for manufacturing chemical 
compounds from wood, that of destructive distillation is probably 
at present the most important. The industry is an old one, and is 
quite well developed in Germany, Russia, Norway, and Sweden, and 
less extensively in France and England. 

[Cir. 36] 

(7) 



8 



The following table gives some idea of the more important data 
pertaining to this industry as compiled by the United States Census 
and the Forest Service of this Department: 

Amounts and values of wood-distillation products in the United States. 





Number 
of estab- 
lish- 
ments. 


Products. 


Year. 


Crude alcohol. 


Acetate. 


Charcoal. 




Amount, j Value. 


Amount. 


Value. 


Amount, j Value. 


1880 


17 
53 
93 
118 
d67 
(d) 


Gallons. 


Dollars. 

86,274 

688,764 

1,976,986 

2,161,813 


Pounds. 
6,593,000 

26,778,415 

86,828,000 
105,141,361 

86,685,129 
103,337,630 


Dollars. 
156,892 
315,430 

981,286 
1,474,982 


Bushels. 


Dollars. 


1890 


1,116,075 
4,945,963 
6,684,870 
5,062,076 
5,273,103 






1900a 


17,154,302 

23,869,055 

« 26, 670, 139 

45,656,720 


726,672 
1,197,973 


1904 6 


1905 c. 


1906/ 




» 











o Capital invested, $5,499,876; cords of wood used, 490,939. 

b Capital invested, $10,506,979; cords of wood used, 586,114, value, $1,783,004; lime used, 523,334 bushels, 
value, $101,068; soda used, 371,780, value, $5,484. 

c Cords of wood used, 659,770, value, $2,010,611. 

d»Hardwood distillation alone. According to statistics collected by the Census Bureau and the 
Forest Service, the average value of hardwood varies from $1.84 to $3.51 per cord. 

« Tar and oil, 677,480 gallons. 

/Cords of wood used, 1,144,896. 

The distribution of the factories in 1900 is shown in the following 
table : 

Distribution of factories and number of hands employed, 1900. 



State. 


Number of 
plants es- 
tablished. 


Wage-earn- 
ers em- 
ployed. 


Pennsylvania 


58 

24 

5 

3 

3 


578 


New York . .. 


354 


Michigan 


169 


North Carolina 


12 


"Wawt Tprtjpv Indiflnn MassAf^hiisett.s 


74 







In the Southern States the distillation of waste pine woods is 
receiving a great deal of attention, but has not yet been placed upon 
a satisfactory business basis. The statistics of this industry for 1905 
as given by the Forest Service and for 1906 by the Census Bureau 
are as follows: 



1905. 

Establishments 15 

Cords of wood used 16, 969 

Value of wood per cord $1. 74 to |3. 00 

Total value of raw material $42, 805 

Products: 

Charcoal bushtls. . 300, 106 

Tar gallons. . 362, 500 

Oil do ... . 434, 780 

Turpentine do. . . . 238, 180 

[Cir. 36] 



1906. 



50, 234 



791, 887 
648, 120 
125, 008 
503, 427 



The quantity and value of acetate of lime (gray) and of wood alco- 
hol exported in recent years are given in the statistical abstracts of 
the Department of Commerce and Labor as follows: 

Acetate of lime and wood alcohol exported 1898-1906. 





Wood alcohol. 


Acetate of lime. 


Year. 






Quantity. 


Value. 


Quantity. 


Value. 




Proof gallons. 
385,938 


Dollars. 


PouTids. 


Dollars. 


189X 


199,230 


37,496,288 


537,856 


1899 


727,062 


414, 875 


48,987,511 


700,000 


1900 


540,799 


320,306 


47,790,765 


776,413 


1901 


919,504 


476,582 


61,296,544 


1,101,037 


1902 


626,925 


338,619 


60,296,544 


962,265 


1903 


833,629 


452,892 


59,449,811 


987,067 


1904 


1,194,466 


585,359 


64,256,945 


1,103,389 


1905 


1,097,451 


603,385 


55,170,131 


1,245,776 


1906 


780,222 


466,467 


69,363,624 


1,950,833 



From these figures it appears that the export trade in wood alcohol 
and acetate of lime, while it fluctuates from year to year, shows a 
notable increase during the past nine years. 

PROPERTIES OF WOOD AFFECTING YIELD OF PRODUCTS. 

Methyl alcohol, acetates, acetone, charcoal, turpentine, wood oil, 
and oxalic acid are directly or indirectly obtained on a commercial 
scale from woods, and the yield is governed largely by the specific 
gravity, weight per cord, and kind of wood, as well as by the manner 
in which the manufacturing process is conducted. Many other farm 
products, such as sugar cane, cornstalks, straws, cotton stalks, etc., 
will yield these products, and it is possible that many other wastes 
ma}^ in the future be utilized in this way. So far, however, but lit- 
tle attention has been given to these materials, and for economic 
reasons they are not commercially employed. 

SPECIFIC GRAVITY AND WEIGHT. 

Different kinds of wood have" different specific gravities, and even 
samples of the same species differ in this respect. Specific gravity 
figures are, therefore, of general value only, and can not be consid- 
ered as strictly applicable to any particular lot of wood. The weight 
of a cord of wood varies not only with the specific gravity of the wood 
but also with the way in which it is piled, a closely piled cord 
weighing, of course, more than a loosely piled one. It has been 
found that as a rule there is 44 per cent of vacant space in a cord 
of wood as usually put up, but 56 per cent of the 128 cubic feet being 
actually wood. These facts undoubtedly account in part for the 
widely different yields so frequently reported and must be considered 
carefully in making calculations of yield of products in which wood 
is usually expressed in cords and not by weight. The specific gravity, 
weight per cubic foot, and ash of certain American woods, as deter- 

4208— No. 36—07 2 



10 



mined by Sharpless, are quoted from the Report of the Tenth United 
States Census. The figures given are the average for different vari- 
eties of the same species. 

Specific gravity and weight of different ivoods. 



Kind of wood. 



Ash 

Oak 

Chestnut 

Bepch 

Birch 

Poplar 

Elm 

Longleaf pine. 
Norway pine . 
White pine... 

Spruce 

Hemlock 

Douglas fir. . . 

Larch 

Maple 



Specific gravity. 



0. 6251 to 0. 
.6540 to . 



7184 
9501 
4504 



.5760 to .6553 



.4854 

.3854 

4051 to .4584 



. 5269 to 



.5157 
.6236 
.6912 



Ash. 




Per cent 




0. 26 to 0. 78 


. 26 to 1. 49 




.18 




.51 


.25 to 


.31 




.96 




.80 




.25 




.27 




.19 


.27 to 


.32 




.46 




.08 




.33 


.33 to 


.54 



Weight per 
cubic foot. 



Pounds. 
38. 9 to 46. 

40. 7 to 59. 

28. 

42. 
35. 9 to 40. 

24 

40. 

43. 

30. 

24. 
25. 2 to 28. 

26. 

32. 

38. 

32. 8 to 43. 



Weight pel 
cord. 



Pounds. 

790 to 3,350 

920 to 4, 220 
2,010 
3,070 

, 570 to 2, 920 
1,740 
2,910 
3,120 
2,160 
1,720 

,810 to 2, 050 
1,890 
2,300 
2 780 

,300 to 3! 090 



WATER CONTENT. 

'The wood used for destructive distillation should be as dry as possi- 
ble, as much time and fuel are wasted if green or wet wood must be 
dried in the retort and the temperature raised under such conditions 
to the point at which distillation begins. For these reasons it is the 
best practice to cut and stack the green wood, which contains from 
20 to 50 per cent of water, from eight months to two years before it is 
to be used in order that it may become well seasoned. Even seasoned 
woods contain from 12 to 25 per cent of water, which must be evapo- 
rated in the retort before the disintegration of the wood begins. 

The capital required to maintain a two years' supply of wood for a 
plant using 20 cords of wood a day varies from $20,000 to $40,000, so 
that in many instances wood not thoroughly seasoned is used in pref- 
erence to making this outlay. Such a practice, of course, increases 
the operating expenses considerably, and drying ovens heated by the 
waste steam and gases of the plant have been used in some cases to 
dry the wood quickly before it goes into the retort. This is un- 
doubtedly the better practice, and whenever it is possible plants 
should be equipped with such drying ovens, thus decreasing the 
amount of capital invested in wood and at the same time securing large 
yields, as during seasoning by exposure w^ood loses weight from rotting 
and from the solution of water-soluble constituents, and consequently 
gives a lower yield of distillation products. 

COMPOSITION. 

The data on the composition of wood are not very satisfactory, as 
most of the figures were obtained by methods less accurate than those 
now in use. Neither were as many normal constituents of woods 

[Cir. 36] 



11 

determined as can now be estimated. In the following table of 
analyses, made by Hugo Miiller, the figures for water extract are 
probably much too low, and include a number of definite and known 
substances, such as tannins, coloring matter, sugars, starch, etc., 
while a number of other definite compounds which it is now possible 
to estimate are covered by the term 'Encrusting matter." 

Analyses of various woods {Miiller). 



Kind of wood. 



Birch 

Beech 

Oak 

Alder.... 

Lime 

Chestnut. 

Fir 

Poplar... 

Pine: 

Willow... 



Water. 


Water 
extract. 


Resins. 


Cellulose. 


Per cent. 


Per cent. 


Per cent. 


Per cent. 


12.48 


2.65 


1.14 


55.52 


1 12. 57 


2.41 


.41 


45. 47 


13.12 


12.20 


.91 


39.47 


10.70 


2.48 


.87 


54.62 


10.10 


3.56 


2.93 


53.09 


12.03 


5.41 


1.10 


52.64 


12.87 


4.05 


1.63 


53.27 


12. 10 


2.88 


1.37 


62.77 


1 13.87 


1.26 


.97 


56.99 


11.66 


2.65 


1.23 


55.72 



Incrusting 
matter. 



Per cent. 
28.21 
39.14 
34.30 
31.33 
29.32 
28.82 
28.18 
20.88 
26.91 
28.74 



It may be said further with reference to these figures that at 
present no definite relation can be established between the composi- 
tion of woods and the chief distillation products obtained from them, 
namely, alcohol, acetic acid, acetone, and charcoal. The data avail- 
able, however, indicate that cellulose gives maximum yields of methyl 
alcohol and but little acetic acid when subjected to destructive distil- 
lation, the latter product being evidently derived chiefly from the 
more unstable 'Encrusting matter." 



YIELD OF DISTILLATION PRODUCTS FROM DIFFERENT WOODS. 

While any kind of wood may be used for the production of alcohol, 
acetates, and charcoal, the hard woods give much larger yields than 
do the soft woods, while resinous woods yield the most turpentine, 
wood oils, and tar. Of the hard woods the maple, birch, beech, and 
oak are preferred, although other woods, such as poplar, elm, willow, 
aspen, and particularly alder, give nearly as high yields. The quan- 
tities of the several products obtained in modern plants from one cord 
of wood are shown in the following table: 

Amount of products yielded per cord of wood. 



Classes of woods. 


Charcoal. 


Alcohol 

(crude) 

containing 

acetone. 


Acetate of 
lime. 


Tar. 


Wood 
oils. 


Turpen- 
tine. 


Gas. 


Hard woods 


Bushels. 
40 to 50 

25 to 40 

25 to 35 


Gallons. 
8 to 12 

2 to 4 

2 to 4 


Pounds. 
150 to 200 

50 to 100 

45 to 75 


Gallons. 
8 to 20 

30 to 60 


Gallons. 


Gallons. 




Resinous woods . . 


30 to 60 


(a 12 to 25\ 
i b2tol0f 




Sawdust (hardwood) 






1 


1 



[Clr, 36J 



a Lightwood. 



b Sawdust. 



12 

The wide variations in quantity obtained from the same class of ma- 
terials are due to differences in quality and weight of the wood used 
and also to different methods of conducting the distillation. The low 
yield obtained from sawdust is rather surprising, and is probably 
explained by the packing of the material in the retorts, owing to 
which fact complete decomposition is rarely obtained. As far as can 
be learned no satisfactory process has yet been devised for distilling 
sawdust. 

APPARATUS FOR DESTRUCTIVE DISTILLATION. 
DESCRIPTION OF EQUIPMENT. 

The apparatus required for the destructive distillation of wood con- 
sists of (1 ) retorts or ovens, in which the distillation is carried on and 




Fig. 1.— Early form of kiln in whicli only charcoal is recovered. 

the chief chemical reactions involved in the production of the crude 
products take place; (2) condensers, in which the condensable vapors 
are liquefied; (3) stills, in which the crude products are separated, 




Fig. 2.— Early form of kiln in whicli charcoal and tar are recovered. 

concentrated, and purified ; (4) mixing pans for the preparation of ace- 
tate of lime, and (5) general apparatus, such as evaporating pans, 
storage tanks, coolers, pumps, etc. 

[Cir. 36] 



13 



^The various forms of kilns in which wood was formerly charred are 
of historic interest, especially in connection with the modern improved 
retorts; but as the yield of alcohol and acetate is very low even in the 
best kilns, these old forms are now employed only in localities pro- 
ducing charcoal iron, where char- 
coal is practically the only product 
recovered. Figures 1, 2, and 3 il- 
lustrate these early forms of kilns. 
The yield of condensed products in 
a kiln, such as is shown in fig. 3, is 
about one-half that from a modern 
retort. 

When attempts were made to 
recover and condense the volatile 
products an air-tight iron retort 
(fig. 4), known as the ^'Swedish 
thermo-kettle,'' set in brickwork 
and connected with a condenser, 

was devised and is still quite extensively employed abroad, where it has 
been in use since 1857. The round retort (fig. 5), which is a modified 
and later form of the above, is made of three-eighths inch steel, is 9 
feet long and 50 inches in diameter, and is provided with a large, 
tightly fitting door at one end and an outlet pipe, about 15 inches in 




Fig. 3.— Early kiln for recovery of alcohol and 
acid. 




///////////////// 

Fig. 4.— Swedish thermo-kettle: A, retort; a, furnace; h, spiral flue; c, tar pipe; d, neck conducting 
the gases; B, drums where tar vapors condense and collect; C, condenser; e, steam pipe; /, pipe 
conducting acid vapors to condenser. 



diameter, connected with the condenser at the other end. The retorts 
are preferably set horizontally in pairs in brickwork, and batteries of 
from 6 to 16 pairs are common. The chief objection to this form of 
retort is that, as usually built, it must be filled and emptied by hand, 

[Cir. 86] 



14 

thus making the cost of operating high. To obviate this objection, 
what is known as the oven retort (fig. 6) was devised and in recent 




Fig. 5.— Round retort with condenser: 1, retort; S, fire walls; S, grate; 4, neck; 6, pipe to condenser; 
6, condenser; 7, trapped delivery pipe; 8, gas pipe; 9, gas main. 

years has been largely used in equipping new plants for hardwood 
distillation. These retorts are rectangular iron chambers, a common 
size being 6 feet wide, 7 feet high, and from 27 to 50 feet long, accord- 




FiG. 6.— A modem Oven retort. 



ing as they are intended to hold two or more cars loaded with wood. 
The ovens are set in brickwork, or are made with double iron walls 

[Cir. 36] 



I 



15 

>Nrith an air space between. They are provided with large doors clos- 
ing air tight and are heated by wood, charcoal, coal, or gas. 

The plant may be assembled and arranged in any desired manner, 
but it is highly desirable that full advantage be taken of natural con- 
ditions, that as much labor as possible be performed by machinery, 
and that the whole establishment be conducted under the most rigid 
control, in order that the plant may be profitably worked and losses at 
any point quickly discovered. Modern plants are equipped with 
either the round or oven retorts. Figures 10, 11, and 12 show 
arrangements of such plants as found in American and German 
practice. 

The condensers (fig. 7) are of the greatest importance; they should 
be sufficiently large to condense all the products even under the most 
adverse conditions, as material lost at this stage can never be recov- 
ered. For separating the constituents of the distillate a simple still. 




^Sh 




=>JL 




Fig. 7.— Types of condensers. 

such as is used in the preparation of distilled liquors, may be used, 
although an iron still is generally preferred in distilling the alcohol 
and acetone from the acetate of lime. For tar storage and settling 
tanks it is customary to use wood; all pipes, pumps, and other 
apparatus through which the acid liquors pass must be of copper or 
wood. 

COST OF PLANT. 



Only approximate figures can be given as to cost and quantity of 
equipment for the destructive distillation of wood, as any figures would 
be greatly modified by the location of the plant, local price of labor, 
freight charges, royalties on patents, and completeness of equipment. 
The first cost of equipment may often be greatly reduced by cheap 
construction and by omitting many labor and time saving devices in 

[Cir. 36] 



16 

apparatus, but such a procedure increases running expenses and is the 
most costly in the end. 

Builders of destructive-distillation plants quote from $1,500 to 
$2,000 per day-cord on a basis of a 10-cord plant, with higher figures 
for smaller plants and lower figures for larger ones. 

The price of equipment when turpentine alone is recovered by dis- 
tilling with steam is, as a rule, considerably lower than the destruc- 
tive equipment, and quotations vary from $400 to $1,500" per cord of 
wood treated daily. These wide differences are due largely to the 
newness of the industry in the South, to differences in time of distilla- 
tion, and also to the fact that in nearly all cases the apparatus is 
patented and an exorbitant value is frequently placed on the patent 
rights. 

A plant to destructively distil 12 cords of wood per day will require, 
approximately, the following equipment : 

2 oven retorts, each 32 feet long, or 12 round retorts. 

4 oven coolers, each 32 feet long, or 100 100-pound charcoal cans. 

24 to 26 charcoal cars of iron (if oven retorts are used). 

1 tar still. 

1 liming still. 

1 alcohol still. 

1 steam pan, 14 feet long, 9 feet wide, inches deep. 

1 settling pan, 8 feet long, 9 feet wide, 4 feet deep. 

1 100-horsepower boiler. 

1 10-horsepower engine. 

1 set iron mixing gear. 

1 blow tank for elevating liquid acetate to settling tank. 

1 storage tank. 

1 mixing tub, wood. 

2 to 3 wooden storage tanks. 

1 copper condenser for each retort. 
1 copper column still aiid condenser. 
Pumps to supply water for concfeneer. 

In the case of pine-wood distillation additional storage and settling 
tanks for tar and turpentine, another tar still, and a^ refining still for 
turpentine are required. Smaller liming and alcohol stills may be 
used. A plant for the recovery of turpentine only would call for 
much less equipment, and the apparatus would be of a different char- 
acter. If a daily charge of 10 cords is to be distilled the following 
items would probably be sufficient: 

10 retorts, capacity of 1 cord each. 

10 condensers. 

1 150-horsepowor boiler. 

1 100-horscpower engine. 

«The higher prices are based on operating each retort but once in twenty-four hours. 
If the time of distillation is shortened, as can safely be -done, the cost per day-cord is 
reduced proportionally. 

[Cir. 36] 



17 

1 refining still. 

1 condensing coil. 

2 hogs for chipping the wood (one in reserve). 
Storage tanks for crude and refined turpentine. 
Pumps and piping for water supply and turpentine. 

These lists of apparatus are merely illustrative, as builders of plants 
must modify their equipment in accordance with experience and 
circumstances. 

MANUFACTURING PROCESSES. 
GENERAL PROCESS OF DISTILLATION. 

The round retorts are filled with the wood by hand, two lengths of 
wood filling a retort, which is made to hold about 1 cord. When 




Wood car used in oven retort. 



ovens are used the wood is loaded on iron cars (fig. 8) holding from 1 to 
3 cords of wood, and from 2 to 8 cars are run into the oven. The 
doors in all cases are made gastight, if possible. The retorts are 
heated slowly and the distillation is continued for from twenty to 
thirty hours, the progress being indicated by the flow of liquor and 
4208— No. 36—07 3 



18 

the gradual heating of the front of the retort from top to bottom. 
When the entire front of the retort has reached a fairly uniform tem- 




FlG. 9.— Charcoal cooler used with oven retort. 



perature the fires are allowed to die down, and, when the retorts or 
ovens are sufficiently cool, the charcoal is removed. 




Fig. 10.— Plan of a modern American destructive distillation plant: A., car; B, retort; C, first 
'cooler; D, second cooler; E, acetate drying floor; a, condensers; b, liquor trough; c, gas main to 
boilers; i, fuel conveyor; m, fire place; n, ash pit; o, hinged spout delivering fuel from i to to. 

If retorts are used the charcoal is placed in covered cans, but with 
ovens, coolers (fig. 9), similar in shape, are used in which the coal 

[Cir. 36] 



19 

is allowed to remain until thoroughly cool. The time required for 
distillation, as already stated, varies from twenty to thirty hours and 
averages about twenty-four hours. The distillate from the retorts 
passes to the condensers (figs. 5 and 7), where the acid, alcohol, and 
other valuable constituents are condensed to liquid form and then 
carried to a large wooden settling tank, which may be either under- 




Pf2=ffl 



Ci 



>//////yy)m;m/w/////m/m mym)/mm////mM " " " ' w//^/////w///\ 



^m 



n 



//////////// 



/////////////}//■ 



9^777777777777777////. 



^7777777//. 




Fig. 11-.— Plan of a refining apparatus: A 1-2, raw liquor vats; B 1-6, raw liquor settling tanks; C 1, 
tar still; C 2-3, raw liquor stills; D 1-2, neutralizing vats; E 1-3, lime-lee stiUs; F 1-3, alcohol 
stills; G, weak alcohol storage tank; H, strong alcohol storage tank. 



ground or overhead, where it is allowed to stand for several days in 
order that the tar may settle. The uncondensed gases pass from the 
condensers to the gas mains (figs. 5 and 10) and are either carried 
directly to the furnace and burned there or go to a gas holder, from 
which they are used. If the tar is not otherwise treated it is blown 
under the boilers with a steam jet and burned. Figures 10, 11, and 

[Cir. 86] 



20 



12 show the general arrangement of plants. The separation and puri- 
fication of the products will be described under the several products. 




m l ^ 



C^ 



Fig. 12.— Plan of Germaa type of fractional distillation plant: A, reservoir for settling pyroligneous 
acid; Bi, tar still; Bi, Bs, liming stills; C, vat for filtered acetate liquor; D, reservoir for crude 
dilute alcohol; E, filter press for acetate liquor; Fi, F-u F3, vats for unfiltered acetate liquor; Gi, G2, 
evaporating pans for acetate; Hi, Hi, Hz, column rectifying still for concentrating alcohol; L, 
milk of lime vat; if, boiled tar car. 

NATURE OF THE REACTIONS IN THE RETORT. 

When hardwood is heated decomposition does not begin until the 
temperature has reached 150° C, the loss below this temperature 
being water alone. With resinous woods turpentine begins to distil 
with water at 97° C. and continues to pass up to about 185° C, over- 
lapping with such products of destructive distillation as may begin to 
pass over above 150° C. Above this temperature (150°)** liquid prod- 
ucts resulting from the decomposition of the wood are distilled. The 
total quantity volatilized, as determined by Violetti, from moisture- 
free hardwood at different temperatures is shown in the following 

table: ' • 

Percentage of wood volatilized at diferent temperatures ( Violetti). 



Temperature. 


Amount 
volatilized. 


Residue. 


Temperature. 


Amotmt 
volatiUzed. 


Residue. 

1 


° C. 


Per cent. 


Per cent. 


°C. 


Per cent. 


Per cent. 


150 to 160 


2.00 


98.00 


260 to 270 


62.86 


37.14 


160 to 170 


5.45 


94.55 


270 to 280 


63.84 


36.16 


170 to 180 


11.41 


88.59 


280 to 290 


65.91 


34.09 


180 to 190 


18.01 


81.99 


290 to 300 


66.39 


33.61 


190 to 200 


22.90 


77.10 


300 to 310 


67.13 


32.87 


200 to 210 


26.86 


73.14 


310 to 320 


67.77 


32.23 


210 to 220 


32.50 


67.50 


320 to 330 


68.23 


31.77 


220 to 230 


44.63 


55.37 


330 to 340 


68.47 


31.53 


230 to 240 


49.21 


50.79 


340 to 350 


70.34 


29.66 


240 to 250 


51.33 


49.57 


350 to 432 


81.13 


18.87 


250 to 260 


58.77 


40.23 


432 to 1,500 


82.60 


17.31 



alt is very doubtful whether alcohol, acid, or tar begins to distil before the temperature of the 
retort reaches 200° C. 
[Cir. ne] 



■''"•IIVERSITY 1 

.... , ■ ^-JRNJ ^^^ 
From these figures it appears that distillation is, fcnrml practical 

purposes, complete at 430° C, as the additional volatilization above 
this temperature is only about 1.5 per cent. The chief products are 
formed continuously throughout the entire process, which proceeds 
in three characteristic periods: (1) At a temperature from 150° to 
280° C, acetic acid, methyl alcohol, and wood creosote are the chief 
products; (2) from 280° to 350° C, large volumes of gases are also 
given off; (3) and from 350° to 430° C, solid hydrocarbons are dis- 
tilled. Chorley and Ramsay*^ have found that the yields of both 
methyl alcohol and acetic acid continue up to about 500° C, or at 
least above 380° C. The quantity of methyl alcohol formed increases 
with rise of temperature to a maximum at about 300° C. and gradually 
falls above that temperature, while the quantity of acetic acid formed 
under the sam6 conditions increases to 350,° with a slight faU in 
quantity between 350° and 450°. Barillot,^ on the other hand, found 
that on a large scale acetic acid ceased to be formed above 300° C. at 
the end of thirteen hours. On the whole, therefore, it appears that, 
while the yields of both alcohol and acid have reached the maximum 
at 300° to 350° C, the formation of both continues up to 450°, beyond 
which point it is useless to raise the temperature. 

Experiments and experience have both shown a lower yield of acid 
and alcohol when the wood was rapidly heated than when slowly 
heated, but the experiments of Chorley and Ramsay just cited show 
that maximum yields of both products may be obtained even when 
distillation is completed in two or three hours. It appears, therefore, 
from the data that the low yields obtained from fast heating in practice 
are due to overheating rather than to rapicl heating. In the case of 
overheating, secondary reactions are set up by the high heat, resulting 
in the destruction of some of the alcohol and acid. This is particu- 
larly liable to occur where no provision has been made to remove the 
products of distillation from the influence of high heat. Further, 
when the vapors are evolved rapidly without provision for their 
prompt removal there is apt to be considerable loss from '^ blowing of 
the retorts,'' that is, the escape of gases around the door due to pres- 
sure within the retort. On the other hand, slow distilling aUows the 
vapors to pass out with less loss from blowing or secondary reactions. 
It is of the greatest importance, therefore, that provisions be made for 
the rapid removal of the vapors from the retort and for their com- 
plete condensation subsequently. 

a J. Soc. Chem. Ind., 1892, 2: 395. 
ftCompt. rend., 1896, 122: 735. 
[Cir. 36] 



22 



SPECIAL FEATURES OF THE DISTILLATION OF PINE, FIR, AND SPRUCE. 

As pine, fir, and spruce contain turpentine and rosin, the process of 
distillation is modified when these woods are used. Figure 13 shows 
some special forms of retorts for distilling pine. The processes in use 
are of two general types: Steam distillation and destructive distilla- 
tion. In the former case live or superheated steam is used to remove 
the turpentine, which is the only product commercially obtained. 
During the heating part of the rosin oozes out of the wood but is 
seldom recovered. When the destructive process is employed the 
procedure differs from hardwood distillation only in the fact that the 
temperature in the retorts should be kept below 200° C. until the 




A ■_ B 

Fig. 13.— Retorts used in distilling turpentine: A, horizontal type; B, vertical type. 

turpentine has been driven off, the aim being to keep the turpentine 
separated from the other products of distillation from which it can 
not be completely purified if they be allowed to mix. So far this 
has not been satisfactorily accomplished on an industrial scale owing 
to the difficulty of preventing local overheating of the retort. 

A great number of retorts both for steam and destructive distilla- 
tion of resinous woods have been invented and patented to meet the 
special conditions arising in distilling these woods. Many of these 
have valuable features, while others have no practical advantage over 
the regular hardwood retorts which have been in use for many years. 
The yield of turpentine will depend on the richness of the wood, ordi- 

[Cir. 36] 



23 

nary pine yielding by steam distillation from 2 to 5 gallons per cord, 
while good light wood yields from 10 to 20 gallons and averages about 
15 gallons per cord, and very rich light wood from 20 to 30 gallons. 
When pine is destructively distilled the yields from good light wood 
are as follows: Alcohol, from IJ to 4 gallons; acetate of lime, from 50 
to 100 pounds; turpentine, from 15 to 25 gallons; tar, 30 to 60 gal- 
lons; charcoal, 25 to 35 bushels; and other wood oils, 30 to 60 gallons. 
Very few operators recover the acetic acid in any form and so far as 
is known none of them recover alcohol. 

There is one other type of process applicable to the treatment of 
resinous woods and a few plants have been built to operate on this 
principle. The wood is treated, in a closed bath connected with a 
condenser, with a liquid having as high a boiling point as rosin, such 
as rosin itself, cotton seed oil, etc. Such a process is applicable for 
the recovery of turpentine and rosin and industrially depends, of 
course, on the use of a solvent cheap enough to make it a financial 
success. 

With reference to the wood turpentine industry in the South it 
may be said that, from a careful examination of a large number of 
plants, the writer is convinced that the distillation industry of the 
South can not be profitable as a whole until fundamental changes in 
equipment and in technical and business management are made. In 
the vast majority of cases the equipment is extremely crude, tech- 
nical knowledge is lacking, and wasteful labor and business conditions 
prevail. Both profits and yields of products could be materially 
increased by improvements in all of these particulars. 

CRUDE PRODUCTS OF DESTRUCTIVE DISTILLATION. 

The crude products from the distillation divide themselves naturally 
into four classes, as follows: 

Per cent. 

(1) Noncondensable gases 20 to 30 

(2) Charcoaf 20 to 35 

(3) Tar and oils 5 to 20 

(4) Aqueous distillate or crude pyroligueous acid 30 to 50 

As has been said, it is the American practice to burn the gases and 
tar under the boilers, particularly in the hardwood districts, but it 
is highly probable that the tar is too valuable to be thus used and 
that it could be more profitably disposed of for other purposes. 

While the chief and most valuable products of hardwood distilla- 
tions are charcoal, acetic acid, methyl alcohol, tar, and acetone, a 
large number of other compounds are produced either primarily or by 
secondary reactions; and, in the aqueous distillate, formic, propionic, 

[Cir. 36] 



24 

butyric, crotonic, and valerianic acids; acetaldehyde, furfuraldehyde, 
methyl-propyl ketone, methyl-ethyl ketone, methyl formate, methyl 
acetate, etc., have been recognized. 

NONCONDENSABLE GASES. 

The gases produced during distillation constitute from 20 to 30 per 
cent of the wood and consist of about 53 per cent of carbon dioxid, 
38 per cent of carbon monoxid, 6 per cent of methane, and the remain- 
ing 3 per cent of nitrogen, hydrogen, etc. These gases are of such 
low illuminating power that they are usually either burned under the 
boilers or retorts or are wasted. 

CHARCOAL. 

The charcoal left in the retort when distillation is complete con- 
stitutes from 20 to 35 per cent of the original weight of the wood, the 
quantity depending on the kind of wood and the manner of heating 
the charge. The physical qualities and chemical composition of 
charcoal are governed chiefly by the temperature at which the wood 
is heated. When heated to about 280° C, wood begins to be friable 
and has a brownish black color. At 310° C: it is friable, takes fire 
readily, and is black in color. The coal becomes harder with further 
rise of temperature and is less readily ignited. As it is only 25 per 
cent as heavy as the wood from which it is made charcoal presents 
some advantages as a fuel, because of lower transportation charges. 
A good charcoal should be thoroughly burned without being brittle 
and should show the woody texture distinctly. The fracture should 
be conchoidal, lustrous, and quite black. It should have few cracks, 
the specific gravity should be high, and it should burn slowly without 
flame or smoke. 

Charcoal is chiefly used in the manufacture of charcoal iron, for 
which purpose it is especially valuable, because of its low phosphorus 
a^d sulphur content. It is also used to some extent as a domestic 
fuel and as an absorbent and clarifier. 

TAR AND OILS. 

Wood Tar. 

The crude wood tar produced when wood is distilled in retorts 
varies from 3 to 10 per cent of the wood. The portion separated from 
the crude pyroligneous acid by settling and that skimmed off of the 
top of the neutralized acid are united, and, after washing with water, 
may be sold in the crude state as '^raw tar" or as '^retort tar." It is 
used for preserving wood, for making roofing felts, as an antiseptic, 

[Cir. 36] 



25 

and for the preparation of wagon grease and other low-grade lubri- 
cants. It is also a suitable raw material for the preparation of anilin 
colors, but finds no industrial application for this purpose, because of 
the low price of coal tar and the fact that the composition of the latter 
is better known. 

In addition to the tar separated by settling, the crude pyroligneous 
acid contains considerable tar held in solution by the acids and alcohol 
present, which is recovered when the crude acid is distilled, and 
constitutes what is known as ''boiled tar." It may be sold as such 
or burned under the retort, or it may be mixed with the raw tar and 
subjected to any desired treatment. 

Wood tar, which varies in character with the kind of wood from 
which it is obtained, is a thick, dark-colored, viscous material still con- 
taining some acetic and other acids, and has a specific gravity of about 
1.05 to 1.15. It consists when derived from hardwood chiefly of 
paraffins, toluene, x^dene, cresol, guaiacol, phenol, and methyl deriva- 
tives of pyrogallol. The tars derived from coniferous woods con- 
stitute the chief tars of commerce, and are particularly rich in 
terpenes, contain considerable quantities of rosin, and have a much 
greater commercial value than those derived from hardwoods. By 
far the greater part of the tar derived from hardwood distillation 
is burned under the retorts. 

The general composition of various tars is shown in the following 
table: 

General composition of various tars. 



Kind of tar. 


Specific 
gravity. 


Acetic 
acid. 


Light 
oils. 


Heavy 
oils. 


Pitch. 


Gas and 
loss by 
distilla- 
tion. 


"Meiler" tar from S. Austrian black fir 


1.075 
1.116 
1.180 


Per ct. 

20 

10 

10 

5 


Per ct. 

10 

5 

10 

20 

8 
18 


Per ct. 
15 
15 
15 
25 

10 
23 


Per ct. 
50 
65 
55 
30 

18 
39 


Per cent. 
5 


" Meiler " tar from Bohemian pine 


5 


Retort tar from Salzburg. . . . . 


10 


Tar from distillation by superheated steam 


5 


Tar from Douglas fir: 

Wood distilled below 700° C 


1.000 
1.075 




Wood distilled below 420° C. 









The crude or raw tar may be handled in several ways. It may be 
burned under the retorts, sold as crude tar, or subjected to fractional 
distillation for the isolation of its several constituents. To effect this 
the tar is placed in a suitable still and heated. When mixtures of 
volatile liquids are heated sufficiently high the distillate does not, as 
a rule, have the composition of the mixture in the still, but the vari- 
ous constituents pass over in a more or less pure form between certain 
definite temperatures. This method of separating the product in the 
still into its various components is known as fractional distillation, 

[Cir. 36] 



26 




(oji7/js/aJ ooo/^ 



[Cir. 36] 



27 

each portion as it distils or passes over being received separately from 
the other portions and called a fraction. Figure 14 shows graphically 
what products are derived from the destructive distillation of wood, 
and the subsequent separation of these products by fractional dis- 
tillation. In the distillation of tar, iron stills are employed and the 
first fraction or portion obtained consists of acetic acid and alcohol 
mixed with some of the light oils. The light oils distil below 150° C. 
and have a specific gravity of from 0.966 to 1.000; the heavy oils 
distil above 150° C, have a specific gravity of from 1.014 to 1.021, 
and contain creosote, toluene, and paraffin bodies. The pitch, which 
constitutes from 50 to 65 per cent of the material, remains in the 
retort when the distillation is complete. 

These several fractions, or portions, may be further purified, acetate 
of lime and alcohol being recovered from the first fraction, while the 
oily distillates are neutralized with milk of lime and redistilled. The 
light oils distilling below 150° C. are used as solvents and for varnish 
making, while those distilling at 150° to 250° C. are treated several 
times with alkali (boiling the alkaline solution in the air to oxidize 
impurities) and acid alternately and redistilled. The distillate 
obtained at from 200° to 250° C. is commercial wood creosote, which 
has a yellow or brownish color and a smoky aromatic persistent odor 
different from that of carbolic acid. This is agitated with strong soda, 
the aqueous layer drawn off is rejected, the remaining oil is mixed 
with sulphuric acid and allowed to stand until creosote oil separates, 
when this is driven off with steam and redistilled finally from glass 
retorts. The creosote obtained boils between 205° and 220° C. and 
has a specific gravity of from 1.030 to 1.080. It contains from 50 to 
60 per cent of guaiacol (C7H7O.OH) and creosote (CgHgO.OH), and 
small quantities of other higher phenols. This product is a powerful 
antiseptic and is used as a disinfectant and preservative. The oils 
distilling above 250° C. are used for burning. 

Stockholm tar and pine tar or pitch, made by distilling pitch pine 
or other coniferous woods in heaps covered with earth (see fig. 2), 
differ in composition from hard-wood and from pine-wood tar made 
in retorts and are regarded as more vahiable. They are used for 
tarring ropes, calking ships, making soaps, for timber preservation, 
pitching barrels, and in preparing medicine. 

Wood Oil. 

When a crude aqueous distillate (see p. 32) is first distilled in order 
to separate acids, alcohol, and acetone from the tar, some of the 
lighter oils which are present distil with the acid and alcohol, and 
finally remain in the alcohol still, or, if distillation is carried further, 
they pass over in the last stages and separate as an oily layer. This 

[Cir. 36] 



28 

oil may be again distilled to recover any alcohol it contains, leaving 
the light wood oil, which is very inflammable and for which no profit- 
able use other than burning has been devised. 

Additional Oils Obtained From Resinous Woods. 

Resinous woods are distinguished from hardwoods in yielding a 
much larger percentage of oils when distilled. Some of these oils 
exist naturally in the wood, while others are derived from the break- 
ing up of natural resins. When wood is gradually heated as in de- 
structive distillation, and the temperature in the retort rises above 
100° C, these oils mixed with water begin to pass over or distil, and 
continue with rising temperature until the distillation of the wood is 
complete. The oil passing from the retort at any moment may be 
different from that which passed previously and from that which fol- 
lows it, so that in practice the distillate is a mixture of compounds 
having closely related chemical and physical properties, and this 
mixture increases in density and the boiling point rises with the 
temperature in the retort. Below the temperature of 250° C. the 
oils are almost colorless, and there is but little if any breaking up 
of the natural resins, those that have distilled being naturally in 
the wood. When, however, the temperature in the retort rises above 
200° C, the wood substance begins to char,, giving to the products 
their characteristic smoky odor. Consequently, ia order to obtain a 
turpentine free from this odor the temperature of the retort must not 
rise above 200° C. until the turpentine is completely distilled.* At 
approximately 250° C. or above the lighter resins begin to break up, 
yielding oils which boil at from 97° to 250° C. When the tempera- 
ture in the retort rises above 300° C. the heavy resins or rosin breaks 
up, yielding 3 to 7 per cent of light oils, known commercially as *' rosin 
spirits" or ^'pinoline," boiling at from 97° to 250° C; 75 to 85 per 
cent of heavy oils, boiling at from 250° to 450° C, known as ''rosin 
oils," and water containing about 1 per cent of acetic acid. The oils 
distilling above 200° C. are contaminated by products derived from 
the breaking up of the wood substance, and these products mask 
especially the odor of the oils specified so that they do not have the 
characteristic rosin-oil odor. !By proper methods of treatment and 
fractional distillation oils of different j)hysical and chemical proper- 
ties may be obtained, and a number of such oils are on the market 
under various trade names. Some cf these oils have not yet found a 
regular sale, however, owing to the fact that their composition is not 
definitely known. 

[Cir. 36] 



. 29 

WOOD TURPENTINE. 

This product when properly made and refined has a specific gravity 
of from 0.860 to 0.880 at 20° C, though the first runnings from the 
still may have a lower and the last runnings a higher specific gravity; 
95 per cent should distil between 150° and 185° C. This turpentine 
closely resembles spirits of turpentine from gum in most of its prop- 
erties, and sells for from 2 to 10 cents less per gallon (depending on 
the care with which it has been refined) than gum spirits, for which 
it has been used as a substitute and adulterant. The processes of 
production and the technical value of this material are now being 
studied,, but as the work is not completed no conclusion as to the 
relative value of wood turpentine as compared with gum spirits can 
be given at present. 

A few words may be of interest, however, as to the best methods of 
producing, refining, and marketing this article. When wood tur- 
pentine was first placed upon the market it was very irregular in 
composition, owing to the fact that but little was known of its nature 
and producers were unacquainted with the proper methods of refin- 
ing. As has been stated, turpentine as commercially produced is not 
a definite compound, but a mixture of closely related terpenes, and 
consequently it differs from moment to moment while distillation is 
taking place and its distilling temperature rises, so that the turpen- 
tine obtained at the close of a distillation is much heavier and differs 
in many ways, particularly in odor and color, from the first runnings 
from the still. This statement applies as well to gum spirits. The 
distiller seldom realizes the importance of this fact as affecting the 
uniformity of this product. In a few instances the gravity of the 
distillate is taken as the turpentine passes from the condensers, and 
if the hydrometer is carefully watched and the specific gravity is not 
allowed to rise above 0.875, the resulting turpentine is fairly uniform 
and satisfactory. As a rule, however, the close of the turpentine dis- 
tillation is determined by the appearance of the oil, the formation of 
beads or foam on the surface indicating that heavier oils are beginning 
to distil. As this point is usually not carefully watched, the result 
is that the product of a plant differs from day to day in color, odor, 
and specific gravity, and its market value is lowered accordingly. 

Although considerable improvement has been made, wood tur- 
pentine still varies greatly in composition, much to its detriment 
commercially. That produced by steam distillation has, in well- 
refined turpentines containing but a small amount of heavy oils, a 
pleasant, fresh pine odor and but little color, while the heavier portions 
of the steam-distilled oils have a more penetrating and lasting odor, 
somewhat resembling that of camphor, and the more of these heavy 
oils the turpentine contains the stronger its odor and the more it 

[Cir. 36] 



30 

differs from gum turpentine in all its properties. Turpentine pro- 
duced by destructive distillation has a pungent, smoky odor, which 
the most careful refining will not entirely eliminate, and is usually 
more highly colored than the steam-distilled product. 

The general character of the turpentine is determined largely, 
therefore, by the method of production, but it is further modified 
by the care with which it is refined. Every precaution should be 
taken to insure that the temperature does not rise sufficiently high 
to drive over the heavy oils. If the refining still is heated directly 
with fire, a thermometer may be placed in the liquid and the heat 
so regulated that its temperature does not rise above 220° C. ; or, 
if the still is properly constructed, the product may be controlled by 
taking the specific gravity of the distilled and cooled turpentine with 
an accurate hydrometer. 

If the crude turpentine is steam refined by passing a current of 
live steam through it, water and turpentine distil together at from 
97° to 99° C, and after the lighter portions of the crude oils have 
distilled, heavier oils, which are always present in crude steam- 
distilled turpentine (owing to the fact that these oils distil below 
100° C. when mixed with water), are also carried over, and these, in 
proportion to the quantity present, seriously affect the specific grav- 
ity, drying properties, and odor of the refined products. It is of the 
utmost importance, therefore, that toward the close of the distilla- 
tion the specific gravity be carefully noted, using an accurate hydrom- 
eter, and when the gravity of the last portions distilling has risen to 
0.875 the distillate should no longer be collected as turpentine. 

By whatever method it is refined, the redistilled turpentine should 
be stored in a reservoir into which a large quantity is run, and from 
which it is barreled from time to time. With these precautions, the 
turpentine will be uniform in specific gravity, color, odor, flash point, 
and drying properties, and will agree closely in many of the physical 
tests with gum spirits, from which it will differ more or less in odor 
and color, according to the method, of production. 

PINE OILS. 

In redistilling, below the temperature of 250° C. in the retort, the 
crude oils obtained in the distillation of resinous woods, there is no 
sharp distinction in properties or composition to be drawn between 
the oils obtained. Thus the oils that pass above 185° C. differ from 
the last fraction of turpentine but little; indeed, there is no clear-cut 
distinction in these oils until rosin begins to break up into rosin 
spirits and rosin oils. For convenience, therefore, all these oils dis- 
tilling above turpentine (185°) and below the temperature at which 
rosin ^'breaks up" may be classified as pine oils, and they may be 

[Cir. 36] 



31 

further fractionated into a number of portions or fractions. These 
oils are suitable for use in making varnishes, soaps, disinfectants, 
paints, inks, etc. 

When, in the distillation of resinous woods, the temperature rises 
above 250° C, not only is the wood attacked, but the resins in the 
wood also begin to break up, so that, with the acids, alcohols, ketones, 
oils, etc., formed from the wood, rosin spirits and rosin oils are formed 
from the rosin, and, if the latter are allowed to mix with the turpen- 
tine driven off at lower temperatures (which is always the case in 
straight destructive distillation), it is impossible to separate them 
perfectly from the turpentine in subsequent refining, because of the 
low boiling point of the rosin spirits. For this reason the odor of 
destructively distilled turpentine differs from gum spirits or steam- 
distilled wood turpentine and closely resembles that of rosin spirits. 

ROSIN SPIRITS. 

This product has a specific gravity ranging from 0.856 to 0.883 
and a boiling point varying from 80° to 250° C. It has a peculiar 
odor, and, with the exception of wood turpentine, is the best substi- 
tute known for gum turpentine, being much used in the manufacture 
of the cheaper grades of varnish and as an illuminant. It contains as 
a characteristic constituent hep tine (C7H12), which boils at 103° to 
104° C, has a specific gravity of 0.8031 at 20° C, and absorbs oxygen 
readily. 

ROSIN OILS. 

Crude rosin oils have specific gravities varying from 0.960 to 1.0, 
while the refined oils vary from 0.960 to 0.990 and boil at from 300° 
to 400° C. They are largely used in the preparation of axle grease 
and other low-grade lubricants; also in the manufacture of printing 
inks, leather dressing, and cement, and as an adulterant for other 
oils. 

TAR OILS. 

The tar oils are obtained by distilling tar, and have many proper- 
ties in common with rosin spirits and rosin oils. Those boiling at 
from 97° to 240° C. closely resemble rosin spirits, while those boiling 
above 240° C. contain phenol, creosote, rosin oils, etc., and, when 
freed from naphthalene and anthracene by cooling and from phenol 
and creosote by treating with alkali, are used as adulterants of 
lubricating oils. 

[Cir. 36] 



32 

AQUEOUS DISTILLATE OF CRUDE PYROLIGNEOUS ACID. 

General Treatment for the Separation of Acetic Acid and Methyl Alcohol. 

This distillate, comprising from 30 to 50 per cent of the weight of 
the wood, contains as its chief constituents, methyl alcohol (4 to 6 
per cent), acetic acid (8 to 14 per cent), acetone (0.2 per cent), and 
tar held in solution by the acids and alcohol present, the balance 
being practically all water contained in the wood and resulting from 
its decomposition. The distillate is a dark red liquid having a strong 
acid reaction and an empyreumatic odor. Its specific gravity varies 
with the amount of water in the wood and the character of wood 
used, but usually falls between 1.020 and 1.050. This crude liquor 
is used to a limited extent in making ''pyrolignite of iron," or ''black 
iron liquor," an impure acetate of iron used in dyeing and calico print- 
ing. There are a number of different methods followed for separating 
the tar from this aqueous distillate and the several valuable con- 
stituents of the latter from each other. As has been said, raw tar is 
usually separated by settling all the liquors in large wooden vats, 
but even under the most favorable conditions the crude liquor still 
contains, dissolved in it, considerable quantities of tar, which inter- 
fere seriously with the purification of acetate of lime and alcohol 
prepared therefrom. In practice one of two general methods is used 
in handling the settled crude liquor: 

(1) It is neutralized directly with lime and the alcohol distilled. 
The resulting calcium acetate is much contaminated with tar^ and 
when evaporated and dried at about 125° C. forms the commercial 
''brown acetate of lime," containing from 65 to 75 per cent of real 
acetate of lime (C2H302)2Ca, the balance being tarry matter, calcium 
carbonate, and water. 

(2) The crude pyroligneous acid without previous neutralization 
is distilled from the tar it contains. This is the better practice, and 
here again one of two procedures may be followed: 

(a) Distil the alcohol, acid, and other volatile constituents, leaving 
only tar (boiled tar) in the still. Then carefully neutralize this dis- 
tillate with milk of lime, force it to a still (lime-lee still, fig. 15) and 
redistil. Alcohol, aldehyde, and ketones pass over, while the acetic 
acid remains in the still in combination with lime. The most perfect 
separation and highest yields are obtained by this method. 

(b) In the second procedure the alcohols, aldehydes, and ketones 
are separated from the acids by fractionation, using a column still 
(fig. 12). The first fractional portion, containing alcohol, acetone, 
and other compounds having low boiling points, but not the acids, is 
received in the alcohol vat until its density reaches 1.000. The 
second fraction or portion contains the acids and is received in the 

[Cir. 86] 



33 



acid vats, distillation being continued until only tar (boiled tar) 
remains in the retort. 

In both cases the substance produced by treating the acid solution 
with milk of lime is known as ''gray acetate of lime." The Uquor 
containing the acetate, whether brown or gray, is pumped to cop- 
per evaporating pans (fig. 12, Gi-Gg), which are usually placed on 
the brickwork over the retort and the solution evaporated until the 
acetate begins to crystallize out, when it is transferred to a drying 
floor and stirred frequently until sufficiently dry. Gray acetate of 
lime contains from 80 to 85 per cent of actual acetate, the balance 
being tarry matters, calcium carbonate, and water. The gray acetate 
is used for the manufacture of 
acetic acid and other acetates 
and is largely employed in calico 
printing. It may be further 
purified by dissolving in water, 
filtering through boneblack, and 
evaporating the solution to 1.16 
specific gravity, when the ace- 
tate, crystallizes in small odorless 
needles which constitute the raw 
material from which acetone is 
made. 

Acetic Acid. 

Commercial acetic acid is pro- 
duced from gray acetate of lime, 
or from the brown acetate pre- 
viously heated to about 230° C. 
to destroy tarry matter, by dis- 
tilling with concentrated hydro- 
chloric acid or with sulphuric ^^' '" ^°^'°^ 
acid (fig.* 16). The lattej* is rarely used, as the calcium sulphate 
formed is difficult to remove from the stills and the impurities in the 
acetate reduce the sulphuric to sulphurous acid, which contam- 
inates the acetic acid. A single distillation yields a slightly col- 
ored solution, containing 30 to 50 per cent of acid, which may be 
further purified by treating with potassium bichromate or perman- 
ganate and redistilling. The first portion of the distillate is con- 
taminated with formic, proprionic, and butyric acids and with 
empyreumatic oils, but the subsequent portions are nearly free from 
impurities. 

Glacial acetic acid is prepared by heating fused sodium acetate 
with concentrated sulphuric acid in a porcelain-lined or earthenware 
still and then distilling, when a nearly anhydrous product is obtained, 

[Cir. 36] 




34 

which crystalHzes if cooled to 16.5° C. It has a specific gravity of 
1.0553 at 15° C. and boils at 119° C. 

The ordinary acetic acid of commerce contains about 30 per cent 
of anhydrous acid, has a specific gravity of about 1.040, and is 
slightly colored. It is used in the preparation of acetates, the manu- 




FiG. 16.— still for preparing acetic acid from acetate of lime, witn detail of acetate pan. 

facture of white lead, and in pharmacy. Some pure acetic acid made 
from wood by distillation is used as vinegar, but such preparations 
have not the characteristics of fruit vinegar. 

In addition to acetate of lime and soda already described (p. 32), 
the following acetates are prepared for industrial purposes: 

[Clr. 36] 



35 

ALUMINUM ACETATE. 

This product is made by dissolving aluminum hydroxid in an 
excess of acetic acid, or by decomposing lead or calcium acetate with 
aluminum sulphate. It is known as ''red liquor" and is largely used 
in dyeing and calico printing. Red liquor made from calcium acetate 
is to be preferred. 

CHROMIUM ACETATE. 

This chemical is made by dissolving chromic hydroxid in acetic 
acid, or by treating chromic sulphate solution with calcium or lead 
acetate. It is used as a mordant in calico printing. 

COPPER ACETATE. 

Copper acetate may be obtained by dissolving verdigris (copper 
carbonate) or copper oxid in acetic acid, but the best is made by de- 
composing a copper-sulphate solution with lead acetate. 

LEAD ACETATE. 

Lead acetate, or sugar of lead, is prepared by dissolving litharge, 
or red lead, in acetic acid, and is used for making other mordants and 
for manufacturing chrome yellow. When excess of litharge is 
employed, basic acetates are produced. 

SODIUM ACETATE. 

Sodium acetate is prepared by neutralizing dilute acetic acid with 
sodium hydroxid or sodium carbonate and concentrating the solution. 
When the sodium acetate crystallizes out, it may be purified by recrys- 
tallization or by fusion. .It is chiefly used in making pure concen- 
trated acetic acid, certain diazo bodies, and as a developer for azo 
dyes in which the color is made on the fiber. 

Crude Methyl Alcohol and Acetone. 

The distillate obtained from the acetic acid or calcium acetate 
(p. 32) in the lime-lee stills contains the following: From 8 to 10 per 
cent of methyl alcohol, acetone (methyl acetate, and some acetic 
acid if the process has not been carefully conducted) , aldehydes, allyl 
alcohol, dimethyl acetone, methylamine, ammonium acetate, small 
quantities of ammonia and amines, oily hydrocarbons, and ketones. 
These latter oily hydrocarbons and ketones render the whole turbid 
when the alcohol is diluted with water. It is necessary, therefore, 
to remove these impurities, which may be done by careful fraction- 
ation of the methyl alcohol in a column still (fig. 12, H^, Hg, Hg), the 
last runnings from which contain the oily impurities, which become 
milky when diluted with water, and should not be allowed to mix 
with the alcohol, but may be further treated by^ again fractionating 

[Cir. 36] 



36 

the last runnings from a number of distillations for the recovery of 
the methyl alcohol which they contain. Or these impurities may be 
removed from the weak alcohol by diluting with water to a specific 
gravity of about 0.935, or until it is turbid from the precipitation of 
the oils and ketones; allow it to stand until these rise to the top as a 
distinct oily layer and remove by skimming. The alcohol may then 
be again distilled in a column still. The product in either case is 
crude methyl alcohol, or ''wood spirit," of a slightly yellow color and 
a specific gravity of about 0.827. This product contains approxi- 
mately 80 per cent of alcohol, 6 per cent of acetone, and 12 per cent 
of water, besides traces of empyreumatic products that give it a disa- 
greeable taste and smell. The crude article is largely used for the 
preparation of formaldehyde, as a solvent in lac and varnish making 
(for which purpose the presence of acetone is rather advantageous), 
and also for denaturing ethyl or grain alcohol for industrial uses. 
By again distilling over lime all but about 3 per cent of water may be 
removed from the crude alcohol, which still contains acetone, etc. 

The compositions and properties of some wood alcohols are given 
in the following table prepared by Klar:" 

Composition of wood alcohols [Klar). 



Kind of wood alcohol. 



Crude spirit from silesiti 

Crude spirit 

Rectified spirit 

Rectified spirit from the Hartz. 

Crude spirit from the Hartz 

Crude spirit, American 

Rectified wood spirits, "A" 

xylolyse 

Rectified wood spirits, "B" 

xylolyse 

Rectified wood spirits, West- 

phalian 



Color. 



Miscibility 
with water. 



Yellow 


Very turbid . . 

Turbid 

Clear 


....do 


White 


do . 


do . 


Yellow 

Yellow-brown 


do 

do 

do .... 


Yellowish 


do 


White 





Tralles. 


Acetone. 


Degrees. 


Per cent. 


80 


6.44 


80 


10.00 


94 


5.60 


92 to 95 


37.46 


85 


20.94 


80 


n.oo 


98 to 99 


4.80 


95 


13.72 


93 to 94 


4.50 



I Spirits re- 
quired to 
decolorize 100 
cc of potas- 
sium bromid 
and bromate 
solution. 



50.00 
15.90 
79.30 
14. .5 
51.20 
65.00 

52.00 

19.40 

70.00 



The specifications adopted by the Treasury Department for methyl 
alcohol for denaturing grain alcohol are summarized as follows: 

The methyl alcohol submitted must be partially purified wood alcohol, obtained 
by the destructive distillation of wood. It must conform to the following analytical 
requirements : 

Color. — This shall not be darker than that produced by a freshly prepared solution 
of 2 cc of tenth-normal iodin diluted to 1,000 cc with distilled water. 

Specific gravity. — It must have a specific gravity of not more than 0.830 at 60° F. 
(15.56° C.) corresponding to 91° of the Tralles scale. 



[Cir. 36] 



a J. Soc. Chem. Ind., 1897, IG; 724. 



37 

Boiling point. — One hundred cubic centimeters slowly heated in a flask under 
prescribed conditions must give a distillate of not less than 90 cc at a temperature 
not exceeding 75° C. at the normal pressure of the barometer (7G0 mm). 

Miscibilitij with water. — It must give a clear or only slightly opalescent s(jlution 
when mixed with twice its volume of water. 

Acetone content. — It must contain not more than 25 nor less than 15 grams per 100 
cc of acetone and other substances estimated as acetone when tested by the method 
of Messinger. 

Esters. — It should contain not more than 5 grams of enters per 100 cc of spirit, cal- 
culated as methyl acetate. 

Bromin absorption. — It must contain a sufficient quantity of impurities derived 
from the wood, so that not more than 25 cc nor less than 15 cc shall be required to 
^decolorize a standard solution containing 0.5 gram of bromin. 

In addition to the above requirements, the methyl alcohol must be of such a char- 
acter as to render the ethyl alcohol with which it is mixed unfit for use as a beverage. 

PURE METHYL ALCOHOL. 

As acetone and methyl alcohol form mixtures having a minimum 
boiling point, it is impracticable to separate them by simple distilla- 
tion, and therefore other means are employed. The alcohol is treated 
with chlorin, which, combining with the acetone, forms chloracetones 
having high boiling points and from which the alcohol may be sepa- 
rated by distillation. Another method is to add iodin and caustic 
soda, which form a precipitate of iodoform with acetone, which may 
be removed by filtration or sedimentation, the alcohol being subse- 
quently distilled. 

Still another method, and the one probably most generally used, 
is to treat the alcohol with calcium chlorid, with which alcohol com- 
bines forming a compound having the formula CaCl2.4CH30H, stable 
at 100° C. This compound is heated gently until the acetone is 
driven off, treated with hot water under pressure, and the methyl 
alcohol distilled. This distillate is again rectified and redistilled 
over lime until it contains from 95 to 99 per cent of alcohol. This 
product is known to the trade as ^^ Columbian Spirits," '^ Louis d'Or," 
''Eagle Spirits," ''Colonial Spirits," or refined wood alcohol, which 
has a spirituous odor, a specific gravity of 0.8142, and boils at 66° 
to 67° C. at 0° It is miscible in all proportions with water, ordinary 
alcohol, and ether, and is an excellent solvent for fats, oils, and resins. 
It is extensively used in the manufacture of anilin colors and smoke- 
less powder, in the making of hats, etc. 



Pure acetone is a colorless liquid having a peculiar ethereal odor 
and a burning taste, a specific gravity of 0.814, and a boiling point 
of 56.3° C. at 0°. It is miscible with ether, alcohol, and water in all 
proportions. Commercial acetone should not have a specific gravity 
greater than 0.802 at 15° C, and four-fifths of it should distil below 

[Cir. 36] 



38 



58.8° C. It is an excellent solvent for resins, gums, camphor, fats, 
and gun cotton, and is largely used in the manufacture of smokeless 
powder, the preparation of celluloid goods, chloroform, iodoform, 
and sulphonal. 

In addition to that produced directly in the distillation of wood 
and separated from methyl alcohol as above described, large quan- 
tities are made from gray acetate of lime by dry distillation at high 
temperature, decomposition taking place according to the following 
formula: (C2H302)2Ca=CaC03 + CH3.CO.CH3. The distillation and 
decomposition is conducted in an iron retort, with constant stirring. 
The distillation takes place in three stages: At first water containing 
a small percentage of acetone comes over; in the second stage, when 
the temperature of the mass has risen to 400° C, acetone oils are 
obtained. The dark brown, highly inflammable distillate separates 
into two layers on standing, the top layer consisting of the so-called 
''heavy acetone oils" and the lower of acetone and light acetone oils 
dissolved in water. The following table gives the percentage yield 
of products obtained by the distillation of gray acetate of lime: 

Products obtained by distillation of gray acetate of lime. 



Products. 


Amount 
present. 


Specific 
gravity. 


Actual 
acetone. 


Acetone water 


Per cent. 

7 to 15 

32 

42 


1.010 
.900 
.930 


Per cent. 
3.0 


Crude acetone 


67.5 


Total distillate . . . 


53.5 







The yield of acetone is about 20 per cent of the calcium acetate, or 
about 13 per cent when made from 40 per cent acetic acid. 

In preparing pure acetone the crude distillate obtained, which con- 
tains higher ketones, aldehydes, etc., is treated with milk of lime and 
allowed to stand for some time. The supernatant oily layer is diluted 
with water and distilled in a column still, yielding as a main fraction a 
nearly pure product (99° to 99.5° Tralles), which does not become 
turbid when mixed with water. Another distillation removes traces 
of aldehydes and empyreuniatic materials. The first and last frac- 
tions obtained in the above distillation, together with oils recovered 
from the clarification with milk of .lime, are mixed and redistilled, 
yielding another portion of commercial acetone. The residual oils 
are the so-called acetone oils of commerce, known as light oils, boiling 
between 75° and 130° C, and heavy oils boihng between 130° and 
250° G. They may be used as denaturing agents, as a means for 
purifying raw anthracene and in secret manufacturing processes. 

[Cir. 36] 



39 

BECOVERY OF CERTAIN WOOD PRODUCTS BY TREATMENT WITH 

CHEMICALS. 

In addition to the distillation methods already mentioned resinous 
woods may be treated by other processes for the recovery of the tur- 
pentine and rosin which they contain. For various reasons these 
processes have received but little attention in the past. Their suc- 
cessful operation requires more chemical and technical knowledge, 
and a more extensive plant than the methods commonly employed 
in recovering turpentine and rosin. Heretofore the value of the 
products, some of which were not utilized, did not justify the greater 
cost of these processes. However, as a good grade of light wood con- 
tains from 15 to 3D per cent of rosin and turpentine which may be 
recovered by chemical treatment, and as the extracted wood is suit- 
able for paper making, present prices justify a brief consideration of 
these processes. 

TREATMENT WITH SODA, SODA ASH, OR VOLATILE SOLVENTS. 

When woods are treated with boiling alkali solutions, with or with- 
out pressure, turpentine is volatilized, and rosin is dissolved together 
with other noncellulose matter. The turpentine distils off and the dis- 
solved matter may be subsequently washed out and recovered as a 
soap, in which form it may be used as sizing material for paper and 
in making soap, or the alkali resinate may be thrown out of solution 
by neutralization and recovered as an impure rosin. In either case 
the rosin or resinate may be destructively distilled, if desired, for the 
preparation of rosin spirits and rosin oils. By burning the residue in 
the retort in a current of air, black ash, an impure alkali carbonate, is 
recovered, which may be used again for the extraction of turpentine 
and rosin. Kosin and turpentine may be recovered in the manufac- 
ture of paper pulp from pine wood by this treatment. 

It has been proposed to recover turpentine and rosin by extracting 
the finely chipped wood with a volatile solvent, such as benzine, 
alcohol, etc. In this case the rosin and turpentine obtained are of 
exceptional purity, but the practicability of recovering the solvent 
economically remains to be demonstrated. This process also involves 
considerable risk from fire. 

Both processes are particularly suited to the treatment of sawdust 
and other finely prepared waste wood, which are destructively distilled 
only with great difficulty. Both of these methods for the recovery 
of turpentine and rosin are now being investigated in this laboratory 
for the purpose of determining their value as industrial processes. As 
far as is known turpentine and rosin are not recovered with volatile 
solvents in actual practice, 

[Cir. 36] 



40 

PREPARATION OF ETHYL ALCOHOL FROM SAWDUST. 

Another product which may be prepared by the chemical treatment 
of wood, preferably sawdust, is ethyl alcohol, which is made by treat- 
ing the wood with sulphurous acid, thus partly converting it into fer- 
mentable sugar, neutralizing, and fermenting with yeasts. 

The alcohol produced is very similar to that produced by hydroliz- 
ing starch with acids and is in every way suitable for industrial pur- 
poses. A yield of 25 gallons of industrial alcohol per long ton of saw- 
dust is claimed for this process. 

Numerous attempts have been made to obtain sugar or alcohol from 
wood by treating it with hydrochloric or sulphuric acid, but the yields 
have not been large enough to make the process commercially 
successful. 

PRODUCTION OF ACETIC ACID AND ACETATES BY FUSION WITH 

ALKALIES. 

As the market for methyl alcohol may be seriously affected, at least 
temporarily, by the use of tax-free denatured ethyl alcohol in those 
industries heretofore using methyl alcohol, any method for increasing 
the yields of the other products of distillation is not without interest 
at this time. In addition to the ordinary destructive distillation 
process, acetic acid may be obtained from wood by submitting it to 
alkaline or acid hydrolysis, or by oxidizing with acids or alkalies. 
The hydrolytic process and oxidation with sulphuric acid do not 
give larger, if as large jdelds, as destructive distillation. Oxidation 
with dilute nitric acid yields from 10 to 18 per cent of acid, while the 
maximum yields are obtained by treating with the alkaline hydrates 
at 200° to 300° C, the yield being from 30 to 40 per cent of the weight 
of the wood together with a considerable quantity of oxalic acid. 
The chief factors governing the yield are the ratio of alkalies to saw- 
dust, the kind of alkali used, the time of heating, and atmospheric 
oxidation. The highest yields are obtained when three parts of 
potassium hydrate are used to one part of sawdust and the mixture 
is heated for a long time with or without exposure to air. 

The procedure is almost identical with that used in the manufacture 
of oxalic acid; and, as would be expected, oxalic acid is also obtained 
in considerable quantity, depending on the temperature at which the 
operation is conducted. No application of this process in this country 
is known to the writer, although it is patented and used in the produc- 
tion of acetates from soda-pulp liquors both in England and Germany. 

[Cir. 36] 



41 



MANUFACTURE OF OXALIC ACID. 



The manufacture of oxalic acid is apparently an entirely neglected 
industry in this country and is one which should receive consideration 
from chemical manufacturers, and could undoubtedly be made an 
industry of considerable value. As will be seen from the following 
table imports are steadily increasing and have reached quite a large 
figure : 

Quantity of oxalic acid imported, 1891-1905. 



Year. 


Amount. 


Value. 


1891 




Pounds. 
2,743,222 
2,889,513 
3,981,768 
4,990,123 
7,906,886 


Dollars. 
200,595 


1895 


189,506 


1899. 


246,027 


1900 


275,747 


1904-5 


360,951 







While from the point of view of the utilization of mill wastes this 
industry must be of minor importance for some time, there seems to 
be an opening for several plants of sufficient capacity to supply our 
home demand, and probably an export trade in oxalic acid could be 
developed, just as has been done in the case of acetate of lime. The 
rapid growth of imports during the past four years promises well for 
the future of this industry in the United States. 

Oxalic acid is prepared from sawdust by fusing with caustic alka- 
lies. To prepare the caustic alkali solution, potassium and sodium 
carbonates are mixed in such proportion that after causticizing (treat- 
ing with lime water, whereby sodium and potassium hydrates are pro- 
duced .and calcium carbonate is precipitated) the proportion of potas- 
sium hydroxid to sodium hydroxid shall be about 4 to 6. A mixture 
of the two salts is dissolved in about 8 times its weight of water and 
made caustic by boiling in an iron pan with slaked lime. After the 
carbonate of lime has settled, the lye is drawn off into another pan 
and concentrated to about 1.3 to 1.4 specific gravity. Sawdust, free 
from large pieces of wood, is now mixed with the lye in such quantity 
that there shall be two parts by weight of alkali to one part of saw- 
dust. The whole is thoroughly mixed, after which all the liquid 
should be taken up by the sawdust. The mass is then spread out 
to a depth of from one-half to three-fourths inch on heating plates of 
iron about 6 feet in diameter, with a 2-inch rim. It is stirred continu- 
ously during the conversion to oxalate. The temperature should be 
raised gradually, but care should be taken that it does not exceed 
240° C, as oxalic acid is destroyed by higher temperatures. To pre- 
vent too high heating it is best to heat the plates with hot gases 
rather than by direct fire, as by the aid of dampers the temperature 

[Cir. 36] 



42 

of the plates can be quite readily controlled. In the first part of 
the process the mass loses water and turns darker until it becomes a 
deep brown and evolves a peculiar odor. When the temperature 
reaches about 180° C, the mass begins to lose color again and becomes 
a greenish yellow. The temperature is then gradually raised to 
240° C, at which point it is held until the mass no longer contains 
particles of wood and is of a greenish white color, the total time 
required being about six hours. The mass is then removed from the 
plates and cooled or immediately dissolved in hot water and the 
liquid concentrated to about 38° B., when it is run into small crystal- 
lizing pans in which, on rapid cooling, nearly all of the sodium oxalate 
separates, leaving potassium carbonate, caustic soda, caustic potash, 
humus compounds, and a little oxalate in solution. The sodium 
oxalate may be freed from the mother liquor by draining and washing 
or by centrifuging. 

The mother liquors are evaporated to dryness, roasted in air, and 
causticized as before for use again. The sodium oxalate is dissolved 
in a very little boiling water, and sufiicient thin milk of lime is run 
in, with constant stirring, to change all of the sodium oxalate to cal- 
cium oxalate and caustic soda. The mixture is run into settling 
tanks, where the oxalate of lime settles out and the supernatant 
caustic soda is run off and concentrated with the first wash water 
from the oxalate, mixed with caustic potash, and used for treating 
another lot of sawdust. After washing, the oxalate of lime is run 
into a lead-lined tank, stirred to a paste with water, and treated 
with dilute sulphuric acid of from 15° to 20° B., in such quantity 
that the mixture contains two equivalents of sulphuric acid to one of 
lime. The whole mixture is kept hot until a test shows no calcium 
oxalate present, when the calcium sulphate is allowed to settle, the 
clear solution containing the oxalic acid is drawn off, and the calcium 
sulphate washed with water. The first washings are added to the 
oxalic acid solution and the remainder is used to mix with the oxalate 
of lime in a subsequent decomposition. The calcium sulphate, or 
gypsum, thus produced may be disposed of as a fertilizer or, as it is 
very pure, may be used as a filler in paper making, or dehydrated 
and used as plaster of Paris. The solution of oxalic acid is concen- 
trated in shallow lead pans until it is, in summer, 15° B., and in 
winter 10° B. It is then cooled to ordinary temperature, when the 
dissolved gypsum separates in cr}^stals. The liquid is further concen- 
trated to 30° B. and crystallized in shallow lead pans. These crystals 
are washed in a minimum quantity of cold water to remove adhering 
mother liquor, dissolved in boiling water, and cooled rapidty, when 
small crystals form. The product is commercial oxalic acid, and 
contains small quantities of sulphuric acid and oxalate of soda or 

[Cir. 36] 



I 



43 

potash, from which it can only be freed by recrystalHzation in from 
10 to 15 per cent hydrochloric acid. The mother liquors, from which 
nearly all of the oxalic acid has been separated, contain the excess of 
sulphuric acid used in setting oxalic acid free and some oxalic acid, 
and are used, after being brought to the desired strength by the 
addition of concentrated acid, for the decomposition of the next lot 
of oxalate of lime. 

Light woods, such as pine, fir, and poplar, give the best yields, 
amounting to about 90 per cent of the weight of the dry wood, while 
the heavy woods — oak, beech, etc. — yield about 80 per cent. 

Oxalic acid is largely used as a discharge in calico printing and 
dyeing, for bleaching flax and straw, for bleaching leather, and in 
the manufacture of formic acid. 

SUGGESTIONS FOR THE DEVELOPMENT OF THESE INDTTSTRIES. 

The industrial processes briefly described in the preceding pages 
separate or prepare from w^ood certain chemical compounds, some of 
which are important articles of commerce, their total value per unit 
of wood being greater than that of the wood from which they are 
obtained. Thus, taking average yields of well-operated plants and 
valuing the products at current wholesale prices, a cord of wood may 
be said to yield the following approximate gross values : 

Hard wood, destructively distilled $11. 00 

Pine (good light wood) 25. 00 

Pine (good, steam-distilled) 7. 00 

Pine extracted with soda, soda pulp made 44. 00 

Pine extracted with volatile solvents and pulp made from residue 46. 00 

Pine extracted with volatile solvents and residue destructively distilled 26, 00 

No figures are given for oxalic acid, for the reason that the industry 
is undeveloped in this country, and while the gross values are much 
greater than those given in the preceding statement for other chemical 
products the cost of production is relatively much higher, and a 
theoretical statement in regard to its production might be misleading. 

It must be fully understood that these values are given merely for 
purposes of illustration and are only approximate gross values, as the 
yield at any one plant may vary widely above or below those given. 
They are based on the yields from well-equipped and carefully operated 
plants using good grades of wood. The several products are priced 
as follows: Charcoal, 4 cents per bushel; 80 per cent alcohol, 30 cents 
per gallon; turpentine, 60 cents per gallon; rosin, $4 per barrel; tar, 
S6 per barrel; gray acetate, $2.50 per 100 pounds; unbleached soda 
pulp, 2 cents per pound. 

From the gross values certain fixed charges must be deducted. 
They are cost of raw material at the plant; cost of operating (labor, 

[Cir. 86] 



44 

management, fuel) ; cost of containers for shipping products ; insur- 
ance, depreciation, and repairs; interest on capital, etc. 

It is beside the purpose of this circular to give an estimate of these 
gross values and fixed charges, and they are only mentioned here in 
order to point out briefly and in general terms some of the ways in 
which an inspection of numerous plants and laboratory work indi- 
cates that the net proceeds of several of the industries may be 
increased. Attention will be confined to a consideration of (1) 
yields, (2) operating expenses, (3) raw materials. As a matter of 
fact, however, these three headings are so intimately associated that 
the effect of any one of them on profits can not be entirely differenti- 
ated from that of the others. 

YIELDS. 

In the destructive distillation of wood the yields obtained in prac- 
tice are much below those given under laboratory conditions. This 
may be due to destruction caused by local overheating in the retorts, 
loss of vapors around the doors of the retorts, incomplete carboniza- 
tion, or imperfect condensation. Losses may also occur from incom- 
plete or excessive overneutralization of acids with milk of lime, or to 
incomplete separation of alcohol and acids from the tar, or of alcohol 
from water. All of these points should receive the constant watchful 
attention of the superintendent, that such losses may be reduced to a 
minimum. Indeed, yields are largely controlled by the experience 
and technical knowledge of the superintendent. The almost total 
absence of chemical control in these industries doubtless accounts for 
many unprofitable plants, the source of whose failure can not be 
otherwise discovered. 

OPERATING EXPENSES. 

Inspection of destructive distillation plants leads to the conclusion 
that the expense of operating is largely increased by the employment 
of hand labor where machinery could often be used to better advan- 
tage. Thus, wood received is often handled several times before it is 
placed in the retorts. Nearly all round retorts are filled and emptied 
by hand. Storage room should be so arranged as to avoid handling 
the wood more than once after it is received. This is possible only 
when oven retorts are used, in which case the wood is not handled 
except when loaded on the retort cars, which are moved by power 
and emptied directly into railroad cars or storage bins, from which the 
charcoal may be taken automatically. 

Great loss of heat and waste of fuel is occasioned by the practice of 
condensing and cooling to ordinary temperature the aqueous distillate 
(p. 32) and allowing it to stand for the purpose of settling out the tar. 

[Cir. 36] 



45 

Such methods appear illogical and unscientific, as the uncondensed 
vapors leaving the retorts contain sufficient heat to separate them into 
their three chief constituents — tar, acetate liquor, and dilute alcohol. 
The process may be greatly simplified in this way, as is shown in the fol- 
lowing comparative statement of present methods and the suggested 
method. The present process involves the following independent 
successive steps: 

(1) Cooling and condensing the tar, acids, alcohols, etc. 

(2) Storing, settling, and separating tar from aqueous distillate. 

(3) Redistilling tar from (2); cooling, condensing, and storing aqueous distillate, 
and storing tar. 

(4) Redistilling aqueous distillate from (2); cooling, condensing, and storing dis- 
tillate, and storing tar. 

(5) Neutralizing, distilling, cooling, condensing, and storing distillate from (8) and 

(6) Fractionating distillate from (5). 

(7) Evaporating, drying, and roasting residue from (5). 

The operations under 3, 4, 5, 6, and 7 require a great amount of heat, 
which is entirely lost in 1, and which is obtained for these operations 
from additional fuel. The operations under 2, 3, 4, and 5 require 
apparatus and storage room, part of which is not needed with the 
modified system. 

Under the modified system the heat lost at (1) in the present 
system is utilized to separate the constituents of the distillate without 
expense for fuel. Thus — 

(1) Receive the tar, alcohol, and acid distillate in a closed still, from which the acid 
and alcohol will be distilled by their own heat. 

(2) Pass the uncondensed vapors through mire of lime; the acids will combine with 
the lime and remain in the mixing vat while the alcohol distils by its own heat. 

(3) Pass the uncondensed vapors of alcohol-water from (2) to a column still, and 
rectify as usual. 

(4) Evaporate, dry, and roast residue from (2), as usual. 

Such a procedure as this is perfectly feasible, can be made continu- 
ous, and will result in the saving of fuel, boiler capacity, apparatus, 
and storage room. Further, it will prevent any losses now due to 
incomplete condensation of vapors, which certainly occur at several 
points in the present system. The process can also be made largely 
automatic, resulting in more regular production, reduction of operat- 
ing expenses, and in general economy and eflftciency of the plant. 
Where resinous woods are distilled the distillate from the tar must be 
condensed in order to separate the turpentine and pine oils from the 
alcohol and acids. 

[Cir. 861 



46 

RAW MATERIALS. 

The annual waste (in lumber sawmills), which is now sold for fuel in 
the United States, is, according to the Forest Service, equivalent to 
approximately 4,000,000 cords of wood, or within 800,000 cords of 
the amount now used in the destructive distillation (1,145,000 cords) 
and paper-making (3,647,000 cords) industries. If to this be added 
the waste, such as tops, lap, and dead and down timber left in the 
woods, this quantity is more than doubled, although no definite figures 
as to the total quantity can be given. The mill and forest wastes from 
resinous woods would yield a large portion of the turpentine and 
rosin now produced and several times as much soda pulp as is now 
made. The waste from the hardwood lumber industry would yield 
more charcoal, wood alcohol, and acetate of lime than is now being 
produced. The sawdust from the Southern pine mills alone will yield 
more oxalic acid than is now used in this country. The spruce and 
hemlock waste will yield at least one-half of the sulphite pulp now 
produced. The question is, Can these industries be most profitably 
conducted in conjunction with the lumber industry, or independently ? 
While, perhaps, a categorical answer applicable to all conditions can 
not be given at present to this question the above-mentioned facts 
strongly indicate that the proper industrial location of the chemical 
industries using wood as a raw material is in conjunction or close 
affiliation with the lumber industry. Such combination means cheap 
raw material and fuel for these industries and increased profits for 
the lumber industry, as well as the removal of waste which otherwise 
seriously interferes with the use of the land and is a constant menace 
from fire. 

It is seen that the gross values obtained per cord of wood are lowest 
when the wood is subjected to steam or destructive distillation, and 
it seems advisable, therefore, that attention be directed more to those 
methods of utilization which give larger gross values. Thus the 
recovery of turpentine and rosin by extracting with soda or volatile 
solvents, and using the residue for paper pulp or for making oxalic acid, 
are promising methods of utilizing pine wood that are receiving some 
attention from paper makers and investors, and their industrial value 
should be carefully determined. The demand for oxalic acid is, how- 
ever, small as compared with available raw material, and could be 
readily supplied by a few well-equipped plants. In general, it may be 
said that all suitable wood should be used in producing the articles of 
greatest value, such as paper pulp, turpentine, and rosin, leaving 
oxalic acid to be obtained from part of the sawdust and destructively 
distilling only that wood which can not be more profitably utilized. 

[Cir. 36] 



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