ANALYTICAL EDITION
May, 1946
pleteness, and finality. No chance is left for misunderstanding or error, and nothing essential to the discussions has been left out, no matter how obvious or well known it may seem to the reader. For example, a full page, containing bot,h dimensional and differential equations, is devoted to “the concept of pressure”. I t is extremely doubtful that the discussion will be understood by any one who does not already have an entirely adequate concept of pressure. For this reason the book is tedious reading. In his preface, the author shows that he set himself the task of writing a book that would meet the needs of every type of person concerned with gas analysis in the fuel-gas industries-to make “instantly available. . . detailed but concise directions, thoroughly indexed, for laboratorj- and plant technicians; theory, mathematical concepts, and literature references for chemists, physicists, and engi-
339
neers; and matters of general interest for executives and persons who usually do not want highly specialized technical information”. Perhaps the author’s way is the only one in which this ambitious and very difficult objective can be attained. Gas analysts are usually individualists, who tend to employ only apparatus and procedures to which they are accustomed and rarely publish data regarding the relative merits of competing analytical processes. The lack of such data, which is the principal defect of thia very valuable tcxt, is consequently not entirely the author’s fault: but in the reviewer’s opinion it should have been possible to give more information of the sort than has been included. The omission of some of the less useful equipment and procedures and the curtailment of some of the more generalized discussions would not be regretted. E. R. W E ~ V B B
CORRESPONDENCE Determination of p,p’ Content of Tech nica-1.DDT SIR: In view of the publication of Cristol, Hayes, and Haller (IND. ENG.CHEM.,A s . 4 ~ED., . 17, 470 (1945)] on the determination of p,p’-DDT in the technical material by crystallization involving the use of 75% ethanol, we wish to place on record the work done in England in the first half of 1943. During our investigations on a suitable method for the manufacture of DDT, we succeeded in preparing material which could be readily isolated as a fine colorless powder, but which had a melting point range of 76’ to 89’ C., and although this was satisfactory for commercial purposes it was very desirable to work out a method which would give us the p , p ’ content, and therefore a measure of its purity. This was accomplished by a direct crystallization from 99.5% alcohol, under a set of standard conditions. The method was coinmunicated to the Ministry of Supply on Feb. 2 , 1944, and in due rourse was incorporated in the British specification for technical DDT. Subsequently, work carried out by the Chief Chemical Inspectorate, Ministry of Supply, led to the use of 99.5% alcohol saturated with pure p,p’-DDT and also to an increase of the volume of alcohol employed, but fundamentally the method was unaltered. Ten grams of the sample were treated with 30 ml. of 99.5% ethanol in a 100-ml. conical flask and brought to the boil to effect solution without loss of solvent. The flask was then set aside and cooled for 2 hours a t room temperature (20° C,). The material was collected on a weighed No. 3 sintered-glass crucible, washed twice with two 6-ml. portions of 75% ethanol, and dried to constant weight at 80’ C. The following results were obtained: Sample KO. 1 2
3 6
69.5 70.0 77.1 77.8 74.8 69.5 69.9
We had previously found t h a t pure Zeidler, Ber., 7,
109.5’ C. (corrected). 88
69.5
103-105° C.
Pharmaceutical Laboratory Geigy Co., Lttl. Trafford Park Manchester 17. Ensland
yG
Melting Point, C.“ 105-7 105-7 105-7 107-9 107-9 106-8 105-7 105-7 DDT had B melting point of 108,51191 (1874), recorded melting point
p , p ’ Content,
I. E. BALABAS R. D. CALVERT
SIR: The work described by us was conducted in the latter half of
1944 and makes use of 75% ethanol saturated with p,p’-DDT as recrystallization solvent. This gave more consistent results, in our hands, than that using stronger ethanol. We are happy, however, at this time t o acknowledge the prior use by Balaban and Calvert of s recrystallisstion technique for the determination of the p , p ’ isomer
content of technical DDT, earlier publication of which was barred by security restrictions. STANLEY J. CRIBTOL Bureau of Entomology and ROBERT A. HAYEE Plant Quarantine 1%.L. HALLER U. S. Department of Agriculture Beltsville, >Id.
Determination of Ethylene SIR: We have tested the method of Francis and Lukasiewics [IKD.ENQ.CHEM.,ANAL.ED., 17, 703 (1945)] for the determination of ethylene and, while we found that the reagent they described absorbs olefins completely and rapidly, we also found that the reagent reacts a t an appreciable rate with carbon monoxide to form rarbon dioxide. Samples of pure carbon monoxide and a mixture of 50% carbon monoxide and 50% nitrogen were tested with the mercuric sulfate solution in a pipet packed with vertical tubes, leaving the sample in the pipet 20 seconds between passes. after 20 passes had been made into the solution the sample was passed into 50% potassium hydroxide solution. The results of these tests are given here: Passes
Pure CO
Pure CO
llixture (507, Nt)
M1.
IMZ.
Ml.
The action of this reagent on carbon monoxide, forming carbon dioxide, may lead to erroneous results when an alkaline absorbent ia used after the mercuric sulfate (such as alkaline pyrogallol solution for determining the oxygen content of a sample) or when the residual gas after absorption in mercuric sulfate solution is used for the determination of paraffin content by measurement of the carbon dioxide produced by combustion analysis. Errors of this type can, of courae, be avoided by passing the gas into caustic solution after it is passed into the mercuric sulfate reagent and correcting any subsequent carbon monoxide determination by the amount of carbon dioxide removed. F. R. BROOKE P. BENJAMIN Shell Development Co.. V. ZAHN Emeryville, Calif. SIR: We appreciate the tests made by Brooks, Benjamin, and Zahn of our reagent for determining ethylene, indicating a possible error in its use, and also a means for avoiding the error. We believe their note will add to the value of the method. A. W. FRANCIS Socony-Vacuuin Laboratories, S. J. LWKASIEWICE Paulsboro, N. J.
