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INDUSTRIAL AND ENGINEERING CHESUSTRY
The yield of tar is ordinarily about 10 to 11 U. S. gallons per net ton of coal, but in some of the new plants the yield is in excess of 12 gallons. F. W. SPERR, JR. T H EKOPPERS COMPANY LABORATORIES MELLON JNSTITUTE, PITTSBURGH. PA. May 11, 1925
. . . . . . . . .. Editor of Industrial and Engineering Chemistry: Mr. Sperr’s criticism of the table which Morrell and Egloff quoted from Tupholme is somewhat inconsistent. He states that the ordinary reader would be misled in assuming that the figures quoted applied to American practice. Mr. Sperr, who had no difficulty in ascertaining that the figures quoted were based on British practice, does not give the ordinary reader credit for sufficient intelligence to do likewise. Reference t o the article quoted by the writers shows this immediately. Tupholme’s work was quoted because it represents a direct comparison of low- and high-temperature carbonization based upon commercial practice by one and the same worker. The criticism of Tupholme’s results, for which the writers are not responsible, should be directed to the proper source. While it is true that the calorific value of the coke-oven gas obtained by Tupholme is low, Tupholme states that it is “poor quality cokeoven gas,” and not, as Mr. Sperr implies, “that coke-oven gas is of poor quality.” So far as the present writers’ comparison of gas produced from low-temperature carbonization and high-temperature carbonization is concerned, the low value given by Tupholme for cokeoven gas (450 B. t. u.’s per cubic foot) makes no difference. He has likewise shown a relatively low calorific value for the gas produced by low-temperature carbonization (average 725 B. t . u.’s per cubic foot), according to very recent figures given by Porter [ J . Franklin Inst., 199, 386 (1925)], who cites values of from 800 t o 950 B. t. u.’s per cubic foot for low-temperature carbonization. The ratio of calorific values for gas from low-temperature and high-temperature carbonization given by Tupholme is 1.61. Porter’s figures show a ratio of 1.54. Using Sperr’s value of 550 B. t. u.’s per cubic foot for high-temperature carbonization, and Porter’s average value of 875 B. t. u.’s per cubic foot for low-temperature carbonization, the ratio becomes 1.59. The relative values then shown by Tupholme are not so far amiss. Presuming that Mr. Sperr is correct in his assumption that British units of measurements were used by Tupholme, which is entirely reasonable, the ratio of U. S. gallons of tar produced by low-temperature carbonization as against that produced by hightemperature carbonization is 2.36. The specific gravity of the low-temperature coal tar was taken as 1.074, while that for the high-temperature tar was 1.184 in arriving a t the figures shown. Here again it is believed that Tupholme’s figures for tar yield by low-temperature carbonization are relatively as low as his figures shown for high-temperature carbonization. The writers in their article assumed a yield of 25 gallons per ton for low-temperature carbonization. Morgan and Soule [Chem. Met., 26, 924 (1922)] have shown yields of 11.3 per cent by weight of the coal which from the data shown by them indicates a yield slightly in excess of 25 gallons per ton. Porter (loc. cit.) shows a yield of 20 t o 25 gallons per ton, while others have shown yields in excess of 30 gallons per ton. Taking Sperr’s average figure of 10.5 gallons of tar per ton for high-temperature carbonization and 25 gallons per ton for lowtemperature carbonization, the ratio becomes 2.37. The relative values shown between low- and high-temperature carbonization when properly interpreted, and all the data and references are given for such interpretation, check quite well with American practice. These figures are shown t o indicate that for comparative purposes there is some value in quoting from British writers
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on the subject, especially when such work is of a comprehensive nature. Most of Mr. Sperr’s discussion is entirely irrelevant to the main contents of the article and the broad purpose of the work presented therein by Morrell and Egloff. His belated criticism of Tupholme’s results and British practice, while of interest, does not concern the present writers. His criticism of the present writers might well have been boiled down t o a single sentence, indicating that no doubts would have been left in the mind of the casual reader, despite the references shown to Tupholme, if the table were labeled “British practice.” JACQUE C. MOIZRELL UNIVERSAL OIL PRODUCTS Co. GUSTAVEGLOFF CHICAGO, ILL. May 22, 1925
Properties of Dogfish Liver Oil Editor of Industrial and Engineering Chemistry: On page 310 of the March issue of THISJOURNAL is a paper by A. D. Holmes and Madeleine G. Pigott on the vitamin A potency of dogfish liver oil. As I have already published the results of some work on this oil, and as no reference is made t o this in their communication, I would like t o point out that in Analyst, 43, 156 (1918), I dealt with the chemical properties of this oil. In a later paper dealing with the liver oil of the tope, Galeus galeus, [Analyst, 47, 203 (1922)] is a definite statement that the dogfish liver oil had been examined physiologically, and that it was found that “as a source of the fat-soluble, growth-promoting accessory substance, it was equal to medicinal “cod liver oil.” The full details of the physiological experiments summarized in this statement are, of course, in my possession. My examination of the liver oil was made incidentally in the course of an investigation dealing with the more or less complete utilization of the dogfish. A. CHASTON CHAPMAN 8 DUKE ST., ALDGATE LONDON, E. C. 3 March 16, 1925
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Editor of Industrial and Engineering Chemistry: Referring t o Mr. Chapman’s criticism, I would say that our paper was devoted primarily t o ‘ a discussion of the vitamin A potency of dogfish liver oil. Our only object in publishing data concerning the chemical and physical characteristics of dogfish liver oil was t o supply sufficient information in this regard so that the readers would have some general idea of the nature of the oil on which we were reporting t h e vitamin A potency. Concerning Mr. Chapman’s comment relative to the information that he had contributed to the subject of the vitamin potency of dogfish liver oil, it may be noted that the paper to which he refers was devoted to a discussion of the physical and chemical characteristics of liver oil obtained from tope, Galeus galeus. Mr. Chapman concludes this paper as follows: I do not know what medicinal or dietetic qualities this oil possesses, but in 1917 Dr. Drummond was good enough to make a t my request an examination of the dogfish liver oil on which I was then working, and found that as a source of the fat-soluble, growth-promoting accessory substances, it was equal to medicinal cod liver oil. Probably tope liver oil would have a similar dietetic value. Thus, his sole contribution t o the subject of the vitamin potency of dogfish liver oil constitutes only a portion of a sentence included in a paper devoted t o a discussion of the chemical and physical characteristics of tope liver oil. ARTHURD. HOLMES THE E. L.PATCH COMPANY BOSTON, MASS. May 19, 1925
