§ 453-] ATROPINE. 389 
Homatropine is a more powerful mydriatic than atropine, and at the 
same time is less toxic. 
§ 453. Tests. —Atropine mixed with nitric acid exhibits no change 
of colour. The same is the case with concentrated sulphuric acid in 
the cold ; but on heating, there ensues the common browning, with 
development of a peculiar odour, likened by Glulielmo to orange flowers, 
by Dragendorff to the flowers of the Prunus padus, and by Otto to the 
Spircea ulmaria —a sufficient evidence of the untrustworthiness of this 
as a distinctive test. The odour, indeed, with small quantities, is 
certainly not powerful, nor is it strongly suggestive of any of the plants 
mentioned. A far more intense odour is given off if a speck of atropine 
is evaporated to dryness with a few drops of strong solution of baryta, 
and heated strongly; the scent is decidedly analogous to that of 
hawthorn blossom, and unmistakably agreeable. 
By heating a small quantity of atropine, say 1 mgrm., with 2 mgrms. 
of calomel and a very little water, the calomel blackens, and crystals 
may be obtained of a double salt; this reaction is, however, given also 
by hyoscyamine and homatropine. Mercuric potassium iodide solution 
and mercuric bromide solution give amorphous precipitates, which, after 
a time, become crystalline, and have characteristic forms. 
A solution of iodine in potassium iodide gives a precipitate with 
acidulated solutions of atropine in even a dilution of 1 : 10,000. Tannin 
precipitates, and the precipitate is soluble in excess of the reagent. 
If atropine be dissolved in dilute hydrochloric acid, and a 5 per cent, 
of gold chloride solution be added, a precipitate of a gold compound 
(C 17 H23N0 3 HClAuCl3) separates. The precipitate is in the form of 
rosettes or needles ; melting-point 137°. On boiling it with water, 
however, it melts into oily drops, and this peculiar behaviour distin¬ 
guishes it from the analogous salt of hyoscyamine, which does not 
melt in boiling water. The percentage of gold left on a combustion 
of atropine gold chloride is 3T35 per cent. 100 parts of the gold salt 
are equal to 46-2 of atropine. A platinum salt may also be obtained, 
(C 17 H 2 3N0 3 HCl) 2 PtCl 4 , containing 29-5 per cent, of platinum. 
Vitali’s test is important; it consists in the production of a violet 
colour with alcoholic potash after oxidation. 
The test may be applied as follows :—Equal parts, say 1 mgrm., of 
nitrate of sodium and of the substance to be tested are rubbed together 
with a glass rod on a porcelain slab, and to this mixture 1 drop of 
sulphuric acid is added ; the mixture is spread out in a thin film ; 
upon this is strewn a little powdered potassium hydrate, and finally 
1 drop of alcohol added ; a violet colour is produced which passes into 
a fine red ; according to the author of the test, 0-001 mgrm. of atropine 
sulphate can by this test be detected. Strychnine obscures this 
reaction. 
