Davy — On a New Chemical Test for Alcohol. 581 



of the liquid under examination, and by employing the strongest 

 sulphuric acid in making the test solution ; for it is very probable 

 that much of the spirit contained in the liquid would be lost during 

 its evaporation in the water-bath. Besides there would be some risk 

 that the indications of the test might be more or less interfered with 

 from particles of dust or organic matter getting into the mixture 

 during that process. 



The reaction which has been described, I should state, is not pecu- 

 liar to ordinary or ethylic alcohol, but is, more or less, readily de- 

 veloped by others — at least I found it to be so in the case of methylic, 

 propylic, butylic, and amylic alcohols, those being the only ones- 

 I had for my experiments. But it is more than probable that some 

 at least of the other alcohols may act in a similar manner ; however, 

 the reaction is much more rapid and striking in the case of ethylic 

 than in that of any of the other alcohols mentioned. I found also- 

 that certain salts of the radicles of those alcohols produced a some- 

 what similar reaction, as well as ethylic ether and aldehyde, and alsa 

 several organic matters which are readily susceptible of oxidation. 



The circumstance that the reaction described is not peculiar ta 

 ethylic alcohol will, no doubt, lessen its value as a positive test 

 for that substance ; but a similar objection appertains to all the 

 other known tests for that compound, as their indications are not 

 peculiar to that alcohol alone, if we except, perhaps, Berthelot's test, 

 which is founded on the development of benzoic ether by the action 

 of benzoic chloride, along with caustic potash on ethylic alcohol. 

 But, owing to the trouble attendant on the preparation of benzoic 

 chloride, and some other practical inconveniences connected with the 

 application of that test, it is not likely that it will ever come ta 

 be one of very general employment. 



The test, however, which I have brought before the Academy has 

 this advantage over those already known, that it far exceeds (accord- 

 ing to my experiments) any one of them in point of delicacy. And 

 though the circumstance that the blue reaction produced in the case 

 of this test is not peculiar to ethylic spirit lessens, as before observed, 

 its value for the detection of that substance, this is just what ren- 

 ders the test of more general applicability ; for by its aid certain 

 impurities or adulterations may be at once detected in different sub- 

 stances or compounds, which in a state of purity should not contain 

 any matter capable of acting on the molybdic solution employed in 

 this test. I may refer to two important substances as examples, viz., 

 chloroform and chloral hydrate, which are now so extensively em- 

 ployed in medicine and surgery for a number of useful purposes ; and^ 

 being agents of great power, it is of much importance that they 

 should be free from the accidental impurities of imperfect preparation, 

 as well as from the frauds of intentional adulteration, which may 

 cither impair their therapeutic value, or even increase the danger 

 of their administration. For there can be but little doubt that in some 

 instances the serious and even fatal effects rcsultiu"- from their use 



