34 Improvements in Physical Science _ (Jax. 
mercury to the beautiful purple fumes which exhale when indigo is 
heated. Hence he concluded that indigo contains a metallic basis. 
This experiment has been confirmed by Dobereiner. He heated 
together 30 grains of the finest Guatimalo indigo and 10 grains of 
mercury in a porcelain dish (constantly triturating the mixture) till 
the purple fumes from the indigo began to appear. He obtained a 
solid amalgam of mercury, which, when heated, exhaled the 
purple fumes of indigo. When digested in sulphuric acid, it com- 
municated a dark blue colour. When put into nitrate of silver, 
crystals of silver were speedily deposited in the form of an artichoke. 
These, being digested in sulphuric acid, coloured it blue, indicating 
an alloy of silver and the metal of indigo. 
Dobereiner conceives that many other vegetable metals exist. If 
these experiments should be confirmed, I think it is high time for 
chemists to examine whether the mere property of combining with 
mercury without destroying the metallic lustre of that body be sufli- 
cient of itself to constitute a metal. This opinion. seems to have 
been adopted on too slight grounds. If Ruhland’s statement 
(Schweigger’s Journal, xiii. p. 359), that mercury amalgamates 
with sulphureted hydrogen and phosphureted hydrogen gases, be 
true, it seems obvious that the mere amalgamation with this liquid 
is not of itself sufficient to prove the metallic state of a body. 
VI. ACIDS. 
1. Sulphuric Acid.—Professor Link, of Breslau, has published a 
set of experiments on the action of sulphuric acid on vegetable 
substances; but I do not perceive any new facts in these experi- 
ments, except that when this acid is digested on sugar or gum a 
quantity of malic acid is formed. 
The general opinion of chemists for some time past has been 
that the fuming sulphuric acid of Nordhausen is an acid free from 
water. This opinion has been lately verified by Dobereiner. He 
made water absorb 58 grains of the fuming acid, and precipitated 
the liquid by barytes-water. The sulphate of barytes obtained 
weighed 170 grains. Now if we allow this salt to contain $4°5 per 
cent. of sulphuric acid, it is obvious that 170 grains of it contain 
57°75 grains of sulphuric acid ; but this is almost exactly the quan- 
tity of fuming acid absorbed by the water. 
2. Chloric Acid.—Vauquelin has obtained this acid in a state of 
purity. He formed chlorate of barytes by the méthod of Chenevix, 
taking care, however, not to employ any acetic acid to facilitate the 
action of the phosphate of silver. ‘This acid possessed the following 
properties :— 
It is colourless ; its taste is acid and astringent; its odour, when 
concentrated, is somewhat pungent. 
It reddens infusion of litmus; it does not precipitate silver, lead, 
nor mercury, from their solution in nitric acid; it does not preci- 
pitate gelatine, notwithstanding its astringent taste, though chlorine 
possesses this property. 
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