May 4, 1906.] 



SCIENCE. 



713 



cent, of water, also attacks calcium with con- 

 siderable rapidity. Alcohol absolutely free 

 from water is not nearly so hygroscopic as is 

 usually supposed; when 200 c.c. of it were ex- 

 posed in a beaker to the air of a laboratory, 

 during fifteen minutes, less than 0.1 per cent, 

 of water was absorbed. 



Almost all , commercial alcohol contains 

 aldehyde in varying proportion. The usual 

 method of removing it is to boil the alcohol 

 with potassium hydroxide until the aldehyde 

 is converted into a colored resin, and then 

 fractionate the liquid, the process being re- 

 peated, if necessary. Obviously, this plan 

 involves a great expenditure of time and 

 material and yet aldehyde-free alcohol is 

 often needed, for example, it is indispens- 

 able in the analysis of fats and oils. Winkler 

 removes the aldehyde by adding to the alcohol 

 a little dry silver oxide, and then a small 

 quantity of potassium hydroxide. The alde- 

 hyde is oxidized to acetic acid and this is 

 neutralized by the alkali. F. L. Dunlap," in 

 a paper which followed Winkler's, suggests 

 that the silver oxide should be formed in the 

 alcohol. This is accomplished by dissolving 

 silver nitrate in a very little water, mixing 

 the solution with the alcohol to be purified, 

 then adding, without shaking, cold alcoholic 

 solution of potassium hydroxide. In this 

 manner a finely divided precipitate of silver 

 oxide is obtained which, in the course of a 

 few hours, completely . oxidizes the aldehyde. 

 The alcohol may be separated from the silver 

 compounds by decantation or distillation; it 

 gives no color with potassium hydroxide. 



NOTES ON ESTERIFICATION. 



The constant use in the laboratory of the 

 esters of organic acids renders any improve- 

 ments in their methods of preparation a matter 

 of considerable general interest. Two papers 

 on the subject containing results of some im- 

 portance, have been published recently. In 

 the first A. Bogojawlensky and J. Narbutt^ 

 record their experiments made to test the ac- 

 tion of various dehydrated metallic sul- 



W. Amer. Chem. 8oc., 28, .395 (1906). 

 •Ber. d. Chem. Ges., 38, 3344. 



phates on mixtures of alcohol and certain 

 organic acids. Of the nine sulphates tried, 

 potassium pyrosulphate and copper sulphate 

 were found to be of the most service and, con- 

 sequently, the majority of the experiments 

 were made with them. The former salt acts 

 equally weU with both aliphatic and aromatic 

 acids, the latter one is best suited for work 

 with the aliphatic acids. 



One of the most interesting results brought 

 out in the paper is the relatively great effect 

 on the yield of ester, of even small quantities 

 of free sulphuric acid or anhydride, such as 

 are almost always formed when a metallic 

 sulphate is dehydrated. This is illustrated 

 by the fact that in an experiment using or- 

 dinary dehydrated ferrous sulphate, the yield 

 of ethyl succinate was 85 per cent., whereas, 

 when the salt, before use, was repeatedly ex- 

 tracted with absolute alcohol, so as to remove 

 traces of sulphuric anhydride, the yield of 

 ester was only 34 per cent. 



In general, the best yield of esters was ob- 

 tained by the use of a dehydrated salt to 

 which about 3 per cent, of its weight of con- 

 centrated sulphuric acid had been added ; next 

 in order comes the use of the dehydrated salt 

 alone and, finally, sulphuric acid alone, as in 

 the ordinary procedure. Another interesting 

 point investigated was to see if a dehydrating 

 agent, which is not acid and can not yield an 

 acid under the conditions of experiment, is, 

 nevertheless, capable of affecting the esterifi- 

 cation. They selected the zeolite chabasite 

 for this purpose, but found it to be without 

 apparent influence on the course of the re- 

 action. 



The method here sketched offers several 

 other advantages besides the question of yield. 

 It can be applied to substances which are de- 

 composed by concentrated sulphuric acid, and 

 the ester, "when formed, may be removed by 

 simply pouring from the salt, without the 

 rather tedious process of neutralization being 

 necessary. 



The esterification reaction has been investi- 

 gated in another direction by J. Wade.^ He 

 finds that the process may be made continuous, 



^ J. Ghem. Soc, 87, 1656. 



