July 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
CONTENT OF SECTIONS OF TABLE111. SELEXIUM NEAR BAYSPRINGS, MISS. LAB. No. B-3175 B-3176 B-3176a B-3177 B-3178 B-3187 B-3179 B-3183 B-3180 B-3182 B-3181 B-3185
MATERIAL Surface soil Yellow sand (0-6 ft.) Limonite scales in sand Yellow sand (6-20 ft.) Iron stone cap of clay Yellow clay beneath cap Black clay with pyrites Pyrites scale Linht-colored scale Wiathered black clay Weathered mixed clay Concentrated extract of weathered clay
A
297
CLAYBED The presence of selenium in gypsum deposits in weathered Pierre shale has also been determined in quantities ranging SELENIUM from 5 to 15 parts per million.2 CONTENT A small number of shales were also collected and their P. p. m. 0.0 selenium content determined in Table IV. 0.0 0.4 0.1 0.3 0.4 0.3 0.6 0.15 0.15 0.20
0.01
The samples reported in Table 111 were obtained from a deposit which is being used as the source of supply of a “medicine.” The clay bank has been excavated t o a depth of about 50 feet. The over-burden is a yellow sandy clay of a maximum depth of about 25 feet. On parts of this sandy slope small pillars of clay are capped with thin scales of limonitic material. Below the sandy layer is a crust of limonitic material about 2 inches thick. This crust is apparently a partly hydrolyzed pyrite layer. Immediately below this crust is a thin layer of yellow clay. Below the yellow clay is a %foot layer of dense black clay containing large numbers of small crystals of marcasite. Below the black clay is a very thin layer of scale consisting largely of marcasite. Below this, and of a thickness not determined, is a deposit of clay somewhat lighter in color than the black clay and containing much smaller quantities of pyrites. The clay layers are used for the preparation of the above mentioned medicine by being allowed to dry and weather, under cover, for a year or more. The weathered material, which contains considerable quantities of ferrous sulfate, is leached with water.
It is unfortunate that this deposit is so low in selenium content, since otherwise it offers a very favorable set of conditions for tracing the course of the selenium in weathering. It is, however, clear that the soil proper is essentially free from selenium, that the weathering produces water-soluble selenium removable by leaching, and that the removal of selenium from the limonitic material does not keep full pace with the removal of the sulfur. This last fact is also indicated by B-3465 of Table 11. In this sample nearly all the sulfur is removed while a considerable selenium content remains, The transfer of selenium by leaching of weathered products, and its relation to sulfur translocation, are also indicated by the presence of selenium in certain shallow wells in the Pierre shale. These waters are high in sulfate content and selenium has been found in quantities as high as 0.07 part per million.
TABLEIV. SELENIUM CONTENT OF ALABAMA SHALES LAB. No.
MATERIAL
B-3191
Dark calcareous shale
B-3188 B-3189 B-3190 B-3195
Dark shale Ferruginous shale Dark shale Light shale
LOCATION
SBLBNIUM CONTENT P . w. n.
3 miles south of
Desmopolis Leeds Leeds Leeds Heflin
0.6 0.15 0.20 0.15 0.15
GENERAL REMARKS It would appear from the data above presented, supplemented by a mass of unpublished data on file in this bureau, that selenium is of much greater distribution in soils and vegetation than has heretofore been suspected. It seems probable that in arid and semi-arid areas the presence of selenium is to be expected in every case where the sulfur content of the soil parent material is high and that, where the selenium content permits, the derived soils and their vegetation may contain suqcient selenium to render them potentially dangerous. The mere presence of selenium in soil is not to be considered a n indication of an inferior soil. It also seems probable that soils produced in humid areas are not likely to have a pernicious selenium content even though the parent materials are relatively rich in this element. If the above inferences be warranted, it would appear that investigations of the selenium contamination of soils should be greatly broadened in scope, and that, in particular, they should cover soils which are to be used under irrigation. LITERATURE CITED (1) Mellor, J. W., “Treatise on Inorganic and Theoretical Chemistry,” Vol. 10, p. 693, Longmans, Green & Co., N. Y., 1930. (2) Ibid., Vol. 11, p. 1. (3) Robinson, W . O., Dudley, H., Williams, K. T., and Byers, H. G., IND.ENG. CHEY.,Anal. Ed., 6, 274 (1934). (4) Smith, P. S., U. S. Geol. Survey, MineraE Resources of U. S., 1917, Part 11, pp. 19-62. RECEIVED March 24,
1934.
Unpublished data, Bureau of Chemistry and Soils.
Constant-Feed Buret and Apparatus for Catalytic Dehydration of Alcohols B. B. CORSON, Universal Oil Products Company, Chicago, Ill. MANY reactions a constant rate of liquid feed is desirable and i t is impossible to obtain an even flow of liquid by means of a n ordinary glass stopcock. The apparatus described below will deliver liquid a t a constant rate over any desired length of time. It operates on the principle of opposing a constant liquid head to a constant resistance. Somewhat similar devices have been described by Sabatier (1) and by Vaughen (8).
For an all-round buret capable of delivering from 15 to 60 cc. per hour, the capacity of A is 500 cc., the length of C is 60 cm., the bore of capillary D is 0.25 to 0.5 mm., and the length of the capillary is 40 em., the vertical height of the spiral being 5 cm. Tube E is of convenience in venting the pressure caused by the insertion of stopper F , and with liquids which tend to deposit solid matter, it is well to protect the capillary by a small filter plug of cotton, G.
The liquid reservoir of the constant feed-buret is essentially a Mariotte bottle, and the head of liquid can be varied at will by raising or lowering tube A ; the effective head is at B, the lower end of tube A, and the range through which the head can be varied depends on distance C . The constant resistance is furnished by capillary spiral D through which the liquid must travel. The choice of feed rate is wide, depending as it does on two variables, the liquid head and the resistance, the latter being governed by the length and the bore of the capillary.
This apparatus has a general application for catalytic reactions in which a liquid is vaporized and the resulting gas passed over a solid catalyst. It is especially convenient for the dehydration of alcohols over alumina. The buret is connected t o the catalyst tube by means of mercury seal H , which is designed along the conventional lines of a mercury seal for a mechanical stirrer. The alumina catalyst is introduced through the open end of the tube a t I , which is then
IK
CATALYTIC DEHYDRATION OB ALCOHOLS
ANALYTICAL EDITION
298
Vol. 6 , No. 4
sealed. The charg-
In the dehydration of the lower alcohols (ethyl, propyl, and butyl) the gaseous olefin passes out at P, water and undecomosed alcohol collecting in receiver 0, whereas in the case of Kigher alcohols such as amyl, liquid olefin also condenses in the receiver.
plug of gJass wool at L. Heat loss is cut down by the insert i o n of a s b e s t o s packing at M and N into the annular space between the catalyst tube and the furnace block. Rec e i v e r 0 can be emptied without dismantling the apparatus, by application of pressure at P with a bulb aspirator, stopcock&being open and stopcock R closed.
This apparatus can be used for any catalytic reaction in which a vaporized liquid is passed over a solid catalyst a t approximately atmospheric pressure-dehydrogenation, dehydration, dehalogenation, etc. Also by the addition of a gas inlet tube a t I , catalytic reactions can be run in the presence of a gas-oxidation, halogenation, hydrogenation, hydration, etc.
ing rate is visible at J. The catalyst is held in place by a perforated glass partition at K and by a
LITERATURE CITED “Catalysis in Organic Chemistry,” p. 351, D. Van Nostrand Company, N. Y . , 1923. (2) Vaughen, IND. ENG.CHEM.,Anal. Ed., 4, 346 (1932). (1) Sabatier,
RECEIVEDMarch 26, 1934.
Thiocyanogen Number WILLIAMJ. WILEYAND AUGUSTUSH. GILL,Massachusetts Institute of Technology, Cambridge, Mass.
T
HE thiocyanogen number is a very useful method of
determining the composition of oleaginous bodies having oleic and linoleic acids or glycerides as constituents.’ With tests conducted according to the customary procedure, however, it seems to be subject to considerable inaccuracy. The usual method of analysis requires 25 cc. of thiocyanogen solution equivalent to 25 cc. of 0.1 N thiosulfate and 0.2 gram of the oil to be analyzed. Since there must be a 50 per cent excess, only 12.5 cc. are used in the reaction. I n the analysis for the iodine number the 25 cc. of Hanus iodine solution are equivalent to approximately 50 cc. of 0.1 N thiosulfate. It is apparent, therefore, that the accuracy of the thiocyanogen number is much less than that of the iodine number, when 25 cc. of solution and 0.2 gram are used in the analysis. I n order to make the thiocyanogen number as accurate as the iodine number, as it should be, since it must be in conjunction with the iodine number in these analyses, it appears that samples of double in size should be used. In order to determine the effect of a larger sample, five different samples of olive oil were analyzed with 0.2 gram of sample and 25 cc. of solution and with 0.4 gram and 50 cc. of solution. I n both cases, the thiocyanogen solution was added from pipets having glass stopcocks on the outlets, in order to give greater accuracy than could be secured from a buret.
TABLEI. RESULTS OF THIOCYANOGEN ANALYSES SAMPLE 1
2
3
4
5
72.78 71.49 72.63 74.46 74.80
73.17 73.42 72.62 78.35 82.97
73.00 74.60 74.39
75.58 75.53
0.2 QRAM 25 CC. E 8 E D
78.05 77.32 77.36 74.00 73.89
77.07 76.55 77.41 75.98 73.52
75.84 76.28 75.63
75.21 75.37 75.69
74.72 73.21 72.92 67.59 68.11 0.4 GRAM 60 CC. U S E D
75.49 75.73 76.00
...
A very wide disparity was encountered in the 0.2-gram sample analyses-a difference which is much greater than would ever be secured in an iodine number. It is obvious. that these analyses would lead to very inaccurate results in the linoleic and oleic acid determinations since the error is so great. With the 0.4-gram sample and 50 cc. of thiocyanogen solution excellent checks were secured. With the exception of the first analysis of sample 4, all were well within the limits of accuracy of the iodine determination. It is therefore recommended that the determination of the. thiocyanogen number should be made with 0.4-gram sample and 50 cc. of thiocyanogen solution. RECEIVED March 20, 1934. 1 Jamieson, G. S., “Vegetable Fats and Oils,” p 345, Chemical Catalog Co., N. Y . , 1932.
Solution of Dificultly Soluble Copper Ores T. H. WHITEHEAD, University of Georgia, Athens, Ga.
I
T HAS been known since the time of Fresenius that sulfide ores of copper may often be extremely difficult to get into solution for analysis. When treatment with mineral acids and ordinary aqua regia fails to effect solution, the author has found that the acid mixture recommended by Bonilla (I) for dissolving nickel metals is very effective. This mixture consists of 40 volumes of 15 M nitric acid and 3‘volumes of 12 M hydrochloric acid. Samples of ore from 0.150 to 3.0 grams are usually dissolved by 43 cc. of the mixture, after boiling for half an hour.
The excess nitric and hydrochloric acids are easily removed by adding 20 cc. of 18 M sulfuric acid after the above treat-ment and heating until the total volume is reduced to 10 cc. This solution can then be diluted with water and the copper’ determined either iodometrically or electrolytically accord-. ing to standard procedures. LITERATURE CITED
(I) Bonilla*c*F.# IN=*ENG* CHnxM.9 RECEIVED June 8,1934
Ed.* 41 12’ (1932)*
