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July, 1919 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY A sample of Merck's urea gave 20.28 per cent car bon against a calculated 19.99 per cent, while sucrose gave 41.98 per cent against a calculated 42.08 per cent. It is probable, as has already been noted by Salter,1 that any oxides of nitrogen which may be formed are reduced in the zinc tube and hence are not a source of error in the determination. SUMMARY A simple, inexpensive apparatus is here reported for the determination of carbon in soils and similar substances by the wet combustion method, using chromic and sulfuric acids. The total time for the determination is about 25 min. Data have been presented`showing that the method as outlined is subject to errors of small magnitude. Div is io n o p Son, Ch e mis t r y a n d Ba c t e r io l o g y Ag r ic u l t u r a l Ex p e r ime n t St a t io n Be r k e l e y , Ca l if o r n ia 637 EFFECT OF EXPOSURE OK RAW LINSEED OIL By E. J. Sh e p p a r d Received October 28, 1918 The most important property of linseed oil is that, when spread in thin layers and exposed to air, it ab sorbs oxygen and undergoes little-known changes in composition, yielding an elastic solid skin. This phenomenon is termed "drying" and on it depends the extensive industrial use of linseed oil in the manu facture of paint, varnish, linoleum, etc. Fig . 2--Ef f e c t o p Ex p o s u r e o n Ra w Din s e e d Oil I * 0.95 Sq. Cm. Surface per Gram Oil II *= 2.00 Sq. Cm. Surface per Gram Oil vestigators. Ballantyne1 allowed linseed oil to stand in an uncorked bottle exposed to light. The oil was shaken daily and at intervals analyzed. Ballantyne found that under these conditions the iodine number decreased, while the specific gravity and acid number increased without a change in volume. Sherman and Falks studied the same question simi larly and found a lower iodine number and higher specific gravity and a small increase in acidity. These authors found a 3.43 per cent increase in specific gravity calculated on the original weight, while ele mentary analysis showed that the oil had taken up 3.16 per cent oxygen. They concluded that the greater increase in specific gravity was probably due to a slight contraction in volume. Sabin3 exposed raw linseed oil in thin films for 8 mo. and found a specific gravity of 1.098 and a gain in weight of not more than 2 per cent. Assuming a specific gravity of 0.932 for the original oil,.Friend4 calculated a contraction in volume of 13.4 per cent for Sabin's film. Thompson? exposed two varieties of raw linseed oil in thin films for 212 days and found Sp. Gr. North American Oil.... 1.16 South American Oil..... 1.15 Gun in Wt. Per cent 8.25 7.70 Decrease in Vol. Per cent ' 13.0 12.4 The changes which take place in linseed oil when exposed to air have been studied by a number of in- 1 Th is Jo u r n a l , 8 (1916), 637. Friend6 oxidized raw Calcutta oil by passing air through the oil and by spreading in thin films on glass. He - found that as the oil gained in weight the density increased, while the volume increased to a maximum and then slowly decreased. Except for the determinations of Sabin, of Thompson, and of Friend, there are no data known to the writer 1 J. Soc. Chem. Ini,, 10 (1891), 29. J, Am. Chem. Soc., 25 (1903), 711; 27 (1905), 605. Th is Jo u r n a l , S (1911), 84. * J. Chem. Soc., Ill (1917), 162. * Trans. Ant. Inst, of Chem. Eng., 8 (1915), 251. * hoc. cit. ;rt~ s '-4./ it T. 633 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. n, No. 7 showing the variation of the constants with gain in weight of raw linseed oil on exposure to atmospheric oxidation. In 1911 the writer exposed two samples of raw linseed oil in shallow glass dishes of approxi mately 12.5 cm. diameter in a dust-proof glass top cabinet which permitted circulation of air. In order to prevent the formation of a sMn, the oils were thor oughly stirred at least twice a day. At intervals the oil in each dish was thoroughly mixed and the specific gravity and iodine number determined, with the re sults as shown in Table I and Fig. 1. Ta b IvU I--Ef f e c t o p Ex p o s u r e o k Ra w Lin s e e d Oil Age Days 0 7 14 21 28 35 42 63 84 105 No r t h Ame r ic a n Sp. Gr. lls* C. 15.5 C, Iodine No. (Hauus) 0.9342 0.9348 0,9355 0.9357 0.9368 0.9372 0.9382 0.9428 0.9561 0.9717 188.4 187.3 186.8 186.8 185.6 18*.6 183.2 177.0 166.4 149.0 La PE.ATA Sp. Gr. 15.5 C. 15.5 C. Iodine No. (Hanua) 0.9323 0.9327 0.9335 0.9336 0.9338 0.9343 0.9353 0.9374 0.9417 0.9485 173,0 172.4 171.9 171.8 171.5 170.0 I68.fi 166.4 160.6 154.9 By withdrawing portions of the oils for determina tion of the constants, the volumes of the oils were gradually reduced, thus increasing the oil surface per gram of oil; or, in other words, decreasing the thickness of the oil layer. Now, since it is well known that, other things being equal, thin layers dry more rapidly than thick layers, these experiments suggested two questions: First, given layers of different thicknesses, are the changes in the constants the same for the same change in weight? Second, what is the quantitative effect of thickness of layer upon the rate of change in the constants? In order to determine the variation of the constants for determined gains in weight, some pure, raw North American linseed oil was exposed in 10 shallow round glass dishes, eight of 9.2 cm. diameter and two of 9.7 cm. diameter, and the dishes kept in a glass top cabinet protected from dust but permitting circulation of air. About 70 g. of oil, accurately weighed, were placed in the eight smaller dishes, and about 36.9 g. in the two larger dishes. Each dish held throughout the test a glass stirring rod. Twice daily each sample was thoroughly stirred and at intervals the gain in weight noted. At longer intervals, the samples, one by one, were removed from the cabinet and certain constants determined. The length of exposure was limited by the formation of a skin, which would de stroy the homogeneous character of the sample, Ta b e s II--Pb r c e n t Ga ik m Ws io h t o s Ra w Lin s s e d On. 0.95 Sq. Cm. OU Surface Age Per Days Gram Oil l --0.05 2 --0.05 3 --0.035 5 --0.025 7 40.01 8 9 6! 03 11 0.04 12 14 0...0..4 16 18 0...0..6 19 20 0...0.7. 22 0.08 23 24 61ii 26 28 6*. is 29 31 61 i$ 34 0.23 37 0,25 39 40 6-28 41 43 6!'33 44 45 0I34 46 47 6135 49 0.39 51 52 6145 53 55 6*48 58 0.525 60 61 62 6.:.6..6 63 0.625 65 66 6! 655 67 68 6169 69 70 6171 2.0 Sq. Cm. OU Surface Per Gram Oil --0,04 --0..0.1. 5 +0.01 o..lo..s 0.065 o..li.o. 0...1.1.5 0.135 6! is 6.`26 0I24 0.32 0.36 0.42 0...4..7 0...5..0 0.61 6170 0.77 0.86 0...9.9. 1.16 1.37 1.74 2...0..0 2,25 2^76 3'.2S 3.71 4.02 0.95 Sq. Cm. OU Surface Age Per Days Gram Oil 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 87 89 91 94 96 98 101 103 105 108 no 112 115 117 119 122 124 126 129 131 133 136 138 140 143 6175 6180 6188 .... 0.92 0.96 iloi 1.11 1.18 1,23 1.36 1.50 1.64 1.79 1.91 2.01 2.21 2.42 2.57 2.80 2.95 3.09 3.41 3.58 3.72 3.93 4.08 4.23 4.49 4.69 4.76 5.00 145 5.09 ,147 5.33 150 5.49 152 5.60 154 5.68 157 5.84 2.0 Sq. Cm. Oil Surface Per Gram Oil 4.14 4.30 4165 4.78 4.96 5.14 5.33 5.58 5l99 6.14 6.31 6.46 6.63 July, 1919 THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY 639 Table II and Fig. 2 give the time-gain in weight CARBON TETRACHLORIDE, CHLOROFORM AND CARBON results. It is worthy of note that all samples showed HEXACHLOR1DE FROM NATURAL GAS1 a loss in weight during the first few days, although a By G. W. Jo n e s a n d V. C. Al l is o n well-settled oil was used. The longer the exposure the paler the oils became; Samples 6, 7 and 8, however, show practically no difference. The amount of oil placed in the large dishes made a layer about one-half as thick as the oil placed in the small dishes. In Fig. 2 the effect of thickness is clearly brought out showing that the thin layer gained in weight about twice as rapidly as the thick layer. Without regard to the thickness of the layers, the evolution of pungent volatile products became dis tinctly noticeable when the oils had gained about one per cent in weight. In Table III are assembled the analytical results shown in Fig. 3. Samples 7 and 8 skinned very slightly when 132 days old; this skin was stirred up with the oil and Sample 7 removed, while Sample 8 was con tinued s days longer, when it skinned again. It is remarkable to note, however, that Sample 10 did not skin, although it had gained about 1 per cent more in weight. There is a change in the specific - gravity curve at the point of skinning of Samples 7 and 8 Received December 21, 1918 As a result of the war, the Government desired the maximum amount of carbon tetrachloride and chloroform to carry on the gas program. A great many of the gases used in modern warfare are derived from these sources. In view of the above fact, and also because after the war :a great amount of chlorine, which is now being used for war purposes, will be turned back toward peaceful enterprises, the Bureau of Mines has7 undertaken a'n investigation on the production of useful products by the chlorination of natural gas and thus utilize part of this excess chlorine. The gas from many fields of natural gas in the United States which yield a pure methane gas, free from the higher saturated hydrocarbons, ethane, propane, etc., is especially desirable for making chlorinated products. The natural gas from several of these fields, notably those in Texas and Louisiana, in locations too far removed from industrial centers and large cities to warrant the expense of piping, could be successfully made into chlorinated products. but no noticeable effect is produced in the iodine num In this report only a preliminary survey of work ber curve. The acid numbers are rather irregular. done on a small scale is given and more elaborate Calculations of the per cent change in volume have results of the investigation will be published as the been made but yield results not so decisive as those work develops. reported by Friend. A large amount of experimental work has been done Tabu s HI--Dat a Sh o w in g t ec s Ef f ec t o f Ex po s u r e o n Raw Lin s eed On, along these lines during the last 23 years but so far Sample Age Gain in Weight Sp. Gr. 15.5* C. No. Days Per cent I5.5C C. Raw 0 0.9345 1 49 0.38 0.9383 2 70 0.69 0.9403 3 98 1.63 0.9481 4 119 3.05 0.9602 5 135 4.22 0.9710 6 148 5.41 0.9840 7 152 5.60 0.9854 8 157 5.84 0.9913 ....9 69 3.67 0.9638 10 86 6.63 Iodine No. Acid (Hanus) No. 188.7 185.2 183.0 174.6 162.8 152.4 141.2 139.2 137.7 157.0 132.6 2.2 2.4 3.0 5.3 7.5 8.5 10.5 11.0 12.1 9.6 14.0 Change OUSurface in per Volume Relative Gram Per cent Viscosity Oil --0.02 -0.07 -0.17 . -0.29 *0,30 -0.10 0.14 --0.22 +0...5.2. 1.00 1.15 1.25 2.00 4.30 7.35 6...0..0 6.95 0.95 0.95 0.95 0.95 0.95 0.95 0.95 2.0 2.0 nothing of practical value, that the authors are aware of, has been accomplished.* The general tendency has been to use a large excess of either chlorine or natural gas to prevent explosion. If a large excess of either gas is used the products desired are hard to separate from the excess of inert gas, since the deposition of the chloroform and carbon tetrachloride depends upon the partial pressure of these products in the gaseous state at the given temperature at which they are separated It was found that 1 g. of each of the oils would easily and completely dissolve in 100 cc. of benzene. The figures in column "Relative Viscosity" are rough approximations only and were obtained by measuring the time required for 10 cc. of the oil to flow from a pipette, taking the time of efflux of the raw oil as 1.00. It will be observed in Fig. 3 that the iodine numbers of the oils in thin layers fall exactly on the curve of the oils in thick layers; while the specific gravity of Sample 9 is not far from the specific gravity curve of the thick layers. and the reaction cannot be controlled to produce the products desired. That the chlorination may work successfully there is required a catalyzer which will cause the reaction to proceed smoothly withqut explosions or deposition of carbon, and which will accomplish the substitution of the chlorine in the methane and ethane molecule according to the reaction CH4+4CI2 = CCI4+4HCI instead of the production of carbon and hydrochloric acid in accordance with the reaction CH4 4- 2 CI2 = C+4HCI. A great many cataly zers will cause chlorine and methane to react, when the temperature is high enough. In fact, no catalyzer is SUMMARY needed at all, but the reaction takes place violently The effect of exposure on certain constants of raw aiid, being exothermic in character, explosively, and linseed oil has been determined over a limited range gives very little, if any, products other than carbon of gain in weight. The thickness of the exposed layer and hydrochloric acid. It is desirable to make the of oil appears to affect only the rate of change in the chlorination complete at one operation, hence if the constants. For any gain in weight over the range desired product is carbon tetrachloride, four volumes covered by these experiments, the changes occurring of chlorine are caused to react with one volume of in the constants appear to be independent of the rate methane (natural gas), or in other Words, the gases of gain in weight. are caused to react in the ratios necessary to Na t io n a l Le a d Co mp a n y St . Lo u is ,'Mis s o u r i 1 Published by permission of the Director of the Bureau of Mines. * Phillips, BaskerviUe, and others.