ON CERTAIN TESTS FOR METHYLIC ALCOHOL. 
109 
go Use requires to be distilled carefully, otherwise some portion of the formic 
acid is carried over with the vapour of the spirit, and on testing it a dark pre¬ 
cipitate is the result. In distilling tinct. iodi co. some portion of the iodine is 
almost sure to be carried over ; but if the distillation is conducted with care the 
small portion that is carried over will not interfere with the test; however, if 
thought desirable, this may be prevented by adding potash to the tincture pre¬ 
vious to distillation. 
Since the reading of my former paper at Bath, a process has been published 
for the detection of methylic alcohol in the presence of ethylic alcohol and vola¬ 
tile oil by Mr. Miller, which is certainly the best and most reliable of all that 
have been brought forward. I do not, however, mean to say that any new 
principle has been discovered, or the new application of an old one, for even 
when the methylated spirit in question was under the consideration of the 
Board of Inland Revenue, Professors Graham, Hofmann, and Redwood reported 
to the chairman that,— 
u Under the influence of oxidizing agents, methylic spirit furnishes together 
with other products a considerable amount of formic acid, whilst alcohol under 
these circumstances yields principally acetic acid. Formic and acetic acids, 
although closely allied in composition and general characters, still offer a greater 
number of points of difference than the two alcohols which they represent. 
Formic acid may be readily distinguished from acetic acid by the facility with 
which the former precipitates the metals from the solutions of the more ea. ily 
reducible metallic oxides, such as oxide of silver and oxide of mercury, which 
are not affected by acetic acid. Unfortunately, this method of testing became 
inapplicable, since it was found that alcohol free from methylic spirit when sub¬ 
mitted to the action of oxidizing agents invariably yields, in addition to alde¬ 
hyde, whiclrcan be resinified and removed by potash, a small quantity of formic 
acid, so that the presence of formic acid among the products of oxidation of a 
suspected liquid cannot with certainty be regarded as an evidence of the exist¬ 
ence of methylic spirit in the original liquid.” 
The method adopted by Mr. Miller in applying the principle of oxidation is 
not capable of being carried out easily nor quickly, but these disadvantages are 
counterbalanced by the certainty which attends the results of the oxidation of 
methylic alcohol. As stated by the learned chemists in their report to the 
Board of Inland Revenue, the presence of a small quantity of formic acid in the 
oxidation products of .a suspected liquid is no proof of the existence of methylic 
spirit in the original; but, as ethylic alcohol only yields a very little, and as 
methylic alcohol yields a great amount of formic acid, its presence in quantity 
after the oxidation of a small portion of a suspected spirit, by whatever method 
it is conducted, points unmistakably to the previous presence of methylic 
alcohol, other sources from which it may possibly be derived of course being 
absent. 
The sources from which formic acid may be derived by oxidation without the 
presence either of ethylic or methylic alcohol are many, so that in every case, 
before applying any method of oxidation to a suspected spirit, we should first 
free it from organic matter by distillation or other process,—albumen, casein, 
gelatine, starch, sugar, both cane and grape, tartaric acid, woody fibre, the 
cereal grains, and many other organic substances yielding formic acid by oxida¬ 
tion; it also exists, as is well known, naturally in ants, some caterpillars, oil of 
turpentine, the stinging-nettle, and, it is said, even in some mineral waters. 
The method given by Mr. Miller in the 1 Pharmaceutical Journal ’ for last 
April, is as follows:— u Now put into the flask 30 grains of bichromate of potash, 
in powder, add half an ounce of water with 25 minims of strong sulphuric acid, 
and then half a fluid drachm of the spirit; allow the mixture to stand fifteen 
minutes, and distil half a fluid ounce. Add to the distillate a very slight excess 
VOL. VII. N 
