INDUSTRIAL AND ENGINEERIfJG CHEMISTRY
984
Calves’ brains inoculated with the digesting mixtures and ripe sludge gave qualitative but no quantitative test for phosphine. That phosphine was not being lost through absorption by the soda lime was confirmed by passing samples of gas known to contain phosphine through the apparatus. Distillation of the contents of the digestion flasks after digestion eliminated the possibility of the phosphine remaining dissolved in the digestion mixture. The absence of phosphine in the gases evolved from the various digestion mixtures confirms the results obtained by Hallefreund, Hallasz, Lemkes, Fresenius and Neubauer, Klett, and Fischer. All of the phosphorus compounds studied gave qualitative tests for phosphine a t various stages in the experimentation, but none were confirmed when the gas was oxidized with chlorine water and the phosphorus determined as phosphomolybdate, using silica-free reagents. This is in agreement with the report by Yakote on the lack of reliability of the qualitative tests. That phosphine did not remain in the digestion mixture was confirmed by passing a stream of nitrogen through the boiling digestion residue. The report by Kulka that digester gas may contain 0.06 per cent phosphine is not confirmed by these experiments. The
Vol. 34, No. 8
concentration of 0.0001 per cent phosphine in digester gas as reported by Rawn, Banta, and Pomeroy (IO) would correspond to approximately 0.015 mg. of silver phosphide from each liter of gas. This quantity is outside the sensitivity of the reagents and apparatus used in the above experiments. On the assumption that phosphine was actually present, this quantity remains as the probable upper limit of phosphine content of digester gases.
Literature Cited Barbieri, Comp. rend., 131, 347 (1900). Fischer, Pfliigers Arch. Ges. Physiol., 97, 601 (1903). Fresenius and Neubauer, 2. anal. Chem., 1, 343 (1862). Hallase, 2. anorg. Chem., 26, 438 (1901). Hallefreund, dissertation, Erlangen, 1890. Klett, 2. Hyg. Infektionskrankh., 32, 155 (1900). Kreps, Pfliigers Arch. Ges. Physiol., 97,601 (1903). Kulka. Zentr. Bakt. Parasitenk., 1, 61, 336 (1912). Lemkes, Chem. Zentr., 1, 604 (1917). Rawn, Banta, and Pomeroy, Proc. Am. Soc. Civil Engrs., 65, P t . 2, 108 (1939). Selmi, Acad. de Bologna, Series 3, p. 8 (1928). Stioh, Chem. Zentr., 1, 14 (1901). Yakote, Arch. Hyg., 50, 118 (1904).
Removal of Metallic Contaminants from Pine Oleoresin Washing with Mineral Acid RAY V. LAWRENCE Naval Stores Station, Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Olustee, Fla.
The use of dilute mineral acid for washing diluted filtered oleoresin, badly contaminated with iron, makes it possible to produce rosin of much lighter color than can be obtained from the unwashed oleoresin. As much as 85 per cent of the metallic contaminants present in crude oleoresin can be removed by washing with dilute mineral acid. No appreciable difference was noted in the effectiveness of the acids used (hydrochloric, nitric, or sulfuric).
OSIN produced in this country is of two types, wood rosin and gum rosin. Wood rosin, along with other constituents, is extracted by a petroleum solvent from resinous stumps and “down wood” of the pine tree. Gum rosin is the residue remaining in the still after the turpentine has been steam-distilled from the oleoresin obtained from the living pine.
R
The flow of oleoresin is induced by periodically wounding certain species of pines. This exudate is collected by attaching metal strips, known as gutters and aprons, to the face of the tree t o guide the oleoresin into a cup which is hung below the freshly wounded portion. The gutters and aprons are usually made of galvanized iron, and the cups are of galvanized iron or clay. The oleoresin eventually removes most of the zinc from the galvanized iron, after which the oleoresin becomes contaminated by the exposed iron. Rosin is graded and sold on the basis of color, the paler colors bringing the higher prices. The color grades of rosin range from a pale yellow in grade X to a dark red (almost black) in grade D, increasing progressively through the grades T V W , WG, N,M, K, I, H, G, F, and E. The color degradation of gum rosin is due principally to iron contamination and, to a lesser degree, t o oxidation products. This is especially true in the medium and lower grades. The presence of 0.1 per cent of iron in rosin is usually sufficient to lower the grade from X to D. Wood rosin that is produced directly from the extracting solvent without refining is ruby red in color and is known as FF wood rosin. The coloring matter present in wood rosin is due principally to organic compounds extracted from the wood by the petroleum solvent. The removal of these color bodies from wood rosin is the subject of numerous patents. Practically all of these patents depend on one or more of the following methods (4): vacuum distillation of the rosin, use of selective solvents for removing the color bodies present in the gasoline solution of rosin, absorption of the color bodies by activated carbon and fuller’s earth, and
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
August, 1942
TABLE I. LABORATORY RESULTSON WASHINGOLEORESIN WITH MINERAL ACIDS Oleoreain % Sample Turpen&in No. tine 1 45 55 1 45 55 55 1 45 2" 21 79 2 42 68 2 42 68 2 42 58 58 2 42 58 2 42 58 2 42 2 42 58 a Crude gum.
No. Grams Acid of WashSample ings Acid Washing Solution 1 100 ml. 0.25 N HCI 363 354 None 1 100 ml.0 25 N HC1 350 400 None 353 None 350 .. None 350 2 1 0 0 m l . 1 N HC1 2 100 ml. 1 N HNOa 350 350 2 1 0 0 m l . 1 N Has04 350 1 1 0 0 m l . 2 N Has04 360 1 100ml. 1 N HaSOi
.. ..
..
No: MI. Washings Water with for Each Rosin Water Washing Grade 2 100 I 2 100 F H None None D 2 100 D 2 100 D 2 100 K K 2 100 2 100 K
... ...
2
the heating of partially decolorized rosin to approximately 300" C. Aside from vacuum distillation these methods are not applicable to the removal of the metallic contaminants from gum rosin. Hey (3) raised the grade of rosin by treating it with zinc and hydrochloric acid. Oliver and Palmer (6), Borglin ( I ) , and Gillet (2) decolorized the iron present in rosin or oleoresin by treatment with oxalic acid. The treatment of rosin or oleoresin with oxalic acid results in the formation of the pale yellow ferrous oxalate, which is practically insoluble in turpentine, rosin, and water. Since the iron oxalate cannot be removed by washing and does not separate by gravity readily, the oleoresin or rosin in solution must be filtered in order to remove the material. If the iron oxalate is not removed, it will decompose when the rosin is heated to the temperature attained in cooking varnish, recombine with the rosin, and cause it to regain its original dark color. Hence, the color of a rosin containing ferrous oxalate is not a true indication of its industrial value. I n a process developed by the United States Department of Agriculture, gum rosin free from dirt and water-soluble impurities (7, 8, 9) is produced by washing the oleoresin with water after it has been diluted with turpentine and filtered. If this diluted oleoresin were washed with an acid solution instead of water, most of the metallic contaminants could be removed. The improvement in color of the product treated in this manner is due to the fact that the iron resinate present
TABLE 11. RE-USEOF ACIDWASHINGSOLUTION
Washing Solution
Rosin Grade
Total Grams Rosin/Gram &SO&
7 Ashin
D
... 16
0.210 0.008
M
M
M M K
100 ml. 1 N HzSO4 Same re-used Same re-used Same re-used Same re-used
I M
K
x K H
32 48 64 80 96 32 64 95 127 159
kosin
0:028 0:021
0.048 0,018 0:023
:
0 053
Iron Content of Used Acid Wash Soln., G. Fe2O.d 100 M1.
...
... ... ..* ... ...
1.56
... ... ...
o:iio
reacts with the mineral acid to form a water-soluble iron salt (other metals usually found in oleoresin have little effect on the color of the rosin). This reaction is reversible, but by using an excess of acid, the equilibrium can be shifted to favor the formation of the water-soluble salt. These soluble salts can be removed from the oleoresin by washing with water. The color of rosin produced in this manner is actually an indication of its purity. The only metal, other than iron, that is found to any ap-
100
K M
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preciable extent in oleoresin is zinc, which also comes from the galvanized cups and accessories commonly used. Although zinc contributes little color to the rosin, it is undesirable in some rosin products. L a b o r a t o r y ex perim e n t s were carried out in which the diluted oleoresin was washed with sulfuric, hydrochloric, and nitric acids for the removal of the metallic contaminants. Using the laboratory results as a guide, the process was tried on a pilot-plant scale with sulfuric and hydrochloric acids.
Laboratory Experiments For the laboratory experiments a stock solution of low-grade oleoresin badly contaminated with iron was diluted with enough turpentine to make the total turpentine content approximately 40 per cent by weight. Three hundred and fifty grams of this solution were mixed by shaking in a separatory funnel with 100 ml. of the acid washing solution previously heated to boiling. When the mixture separated, the washing solution was drawn off. The diluted oleoresin was then washed twice with 100-ml. portions of hot distilled water. After the separation of the wash water, the diluted oleoresin was steam-distilled in the usual manner. Check distillations were made on the undiluted crude oleoresin (sample 2 ) , the unwashed diluted oleoresin, and the diluted oleoresin that had been washed twice with 100-ml. portions of distilled water. The results of these experiments are given in Table I. RE-USEOF ACID WASHINGSOLUTION.A series of runs was made to determine the extent to which the acid washing solution could be re-used before the iron concentration became great enough to lower its effectiveness. A stock solution of the same low-grade oleoresin was used. A 300-gram sample of this solution was washed with 100 ml. of the acid washing solution a t approximately 80" C. by thoroughly mixing in a separatory funnel. A second 300gram sample of the oleoresin was washed in like manner with the washing solution which had been separated from the first sample. This procedure was continued until the color of the oleoresin was not appreciably improved by washing with the acid solution. After the acid was drawn off, each sample was washed twice with 100-ml. portions of distilled water. The results of these runs are listed in Table 11.
Pilot-Plant Experiments Pilot-plant work was based on the laboratory work as a guide. As the laboratory experiments showed little difference between the various acids tried, only hydrochloric and sulfuric acids were used for the pilot-plant experiments. Runs were made with 2, 4, and 6 liters of normal and 2 normal solutions of each acid. The charge of crude oleoresin was 9 to 11 kg. The oleoresin was principally from longleaf pine and contained a considerable amount of scrape. To eliminate sampling difficulties, the scrape was allowed to settle out and the top portion was decanted and used in these studies. This top portion of the oleoresin was thoroughly mixed each time in order to secure a representative sample for each charge. The crude oleoresin was weighed and charged into the melting tank, and sufficient turpentine was added to bring the content to approximately 40 per cent. The tank was capped and the charge was heated to looo C. As soon as the charge
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TABLE111. PILOT-PLANT DATAox REMOVAL OF METALLIC CONTAMINANTS FROM PIKEOLEORESINBY WASHING WITH MINERALACID Sample t o ,Melting Tank
wt. of
Sample No. 1
2
3
4
5
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INDUSTRIAL AND ENGINEERING CHEMISTRY
~~~
Wt. of turpentine sample, added, kg. kg. Crude 9.08 3126 3.26 9.08 3.26 9.08 10.00 3.63
Acid Added t o Wash Tank Total Moles vol .. acid kg. Acid concn liter's gum
.
........
"die 4 4 4
2 N HC1 1 N HC1 2 N HC1
10.50 10.90 9.53 9.66 9.53 10.90 10.80 10.90
3.75 3.85 3.40 3.49 3.26 3.85 3.85 3.85
None None 4 2 6 2 4 2
Crude 11.10 11.10 10.90 11.10 11.10 11.10 11.10
3:99 3.99 3.85 3.99 3.99 3.99 3.99
None 2 2 4 4 6
Crude 11.10 11.10 11.10 11.10 11.10
3:99 3.99 3.99 3.99 3.99
4 4 6
Crude 11.10 11.10
3:99 3.99
None 6
6
..
3 2 2 2
0:ss 0.44 0.80
..
i'Fiici'
1 N HC1
1N 2N 2N 2 hr
HC1 HC1 HCI H2904
........ 1 2 1 2 1 2
.N. . His04 ..... N N N N N
HzSOa HzSOI &SO4 H~SOI HsSO,
........
...
Nnne 6
NO. Washings with Water
........
3 3 2 2 2 2 2 2
0:42 0.21 0.63 0.37 0.74 0.37
.. o:is
0.37 0.36 0.72 0.54 1.08
3 2 2 2 2 2 2
..
..
0:54 0.72 0.72 0.54
3 2 2 2 2
........
..
..
2 N Hi304
1:os
1 iXr H&Oa 2 N Hd301 2 N HC1 1 S HC1
...
........
3 2
Rosin Grade5
G G M K M
++ 0.1 0.1 + 0.7 + 0.9 + 0.3
D
D
H f 0.3 F H 0.9 H 0.5 K 0.9 H 0.9
+ + + +
F E H+O
:+'+
K K K
00.3 0.8 0.5 0.9
++ H + 0.0 G + 0.6 K + 0.5 K + 0.9 K + 0.0 I( + 0 . 2 W W + 0.8 WG + 0.7 x + 0.1
a Determined by photoelectric photometer to the nearest 0.1 grade; e. g., I
