96 Dr. It. D. Thomson, on the Male of Testing Alcohol. 



liquor contain any acotic acid, this may be saturated previous to distilla- 

 tion with carbonate of soda, if the amount should be considerable, in 

 order to remove the vinegar smell which might interfere with the odour 

 of the subsequent test. Into the distilled liquor, supposed to contain 

 alcohol, should be dropped a crystal or two of chromic acid, and the liquor 

 stirred. If the smallest quantity of alcohol is present, the green oxide 

 of chrome will begin to be disengaged, and at the same time the smell of 

 nldohyde is distinctly perceptible. 



The production of the aldehyde from the alcohol depends on the 

 separation of ogygen from the chromic acid, its union with the hydrogen 

 of the alcohol, and their consequent removal in the form of water ; the 

 formula) for the two bodies being, 



C 4 H 5 + HO Alcohol 



C 4 H 3 + HO Aldehyde 



H 2 



By means of this simple test, it is possible to distinguish a drop of 

 alcohol in half-an-ounce and even in an ounce of water. When chromic acid 

 is not at hand, the experiment may be made with bichromate of potash, 

 and sulphuric acid. This perhaps affords the most distinct method of 

 performing the experiment, and may be conducted as follows : — Drop in 

 a few grains of powdered bichromate, into a small test glass (which tapers 

 towards the bottom,) containing the solution to be examined, and add a 

 few drops of oil of vitriol. If alcohol is present, the green oxide will be 

 observed to form on the surface of the undissolved salt, and the charac- 

 teristic odour of aldehyde will speedily be perceptible. As an instance 

 of the utility of this test, it is only necessary to give one illustration. 

 Some months ago I had sent to me by Dr. Joseph D. Hooker, a bottle 

 containing 7 cubic inches of a fluid which was obtained from a species of 

 Eucalyptus, or gum-tree, in Van Dieman's Land, a fluid which is drunk 

 by the natives as an intoxicating liquor. It possessed a powerful odour 

 of vinegar, to such an extent, that it overcame every other smell which 

 might be present. On neutralizing it with carbonate of soda, it was found 

 to require 28*6 grains of this salt to saturate the acid, equivalent to 10 12 

 grains of dry acetic acid in the whole fluid. On distilling one-third of 

 the liquor, a fluid came over having a faint odour of foreshot. When 

 chromic acid was added to it, or bichromate of potash and sulphuric acid, 

 the liquor became green, and the odour of aldehyde was powerfully 

 evolved. This proved the presence of alcohol. On evaporating the 

 liquor in the retort, a small quantity of sugar, and needle-shaped crystals 

 remained. The latter when treated with sulphuric acid, gave out a strong 

 smell of acetic acid. These were satisfactory proofs that the eucalyptus 

 sugar is capable of fermentation, and that the alcohol produced from it 

 is convertible into acetic acid — facts which show us that the Australian 

 sugar is not manna or peculiar but, common sugar. 



