70 “REPORT—1848. 
heated to ignition, it swells up enormously, giving off at the same time a very 
perceptible smell of aceton and burns, leaving at last a considerable quantity 
of ash, which consists of the carbonates of lime, magnesia and potash. It is 
without doubt the acetates of those bases which, being mixed with the sub- 
stance, produce the smell of aceton during ignition. ‘The acetic acid was of 
course derived from the basic acetate of lead used in the preparation of 
xanthin, and the acid with which they were originally combined must have 
gone to the oxide of lead. Now, as I stated above, the oxide of lead was 
found to be combined with phosphoric acid; hence it is probable that the 
greater part, if not all, of the fixed bases left after the ignition of the xanthin 
existed in the plant as phosphates. Xanthin has a disagreeable taste, between 
bitter and sweet. The watery sclution is yellow. It is soluble in alcohol, 
and is left after evaporation in the same state as before. It is insoluble in 
gether. On adding muriatic or sulphuric acid to the watery solution and boil- 
ing for some time, a peculiar smell is evolved, the solution becomes gradu- 
ally dark green, and a dark green powder is deposited. ‘This is the most 
characteristic property of xanthin. Nitric acid does not produce the same 
dark green powder, or any deposit on boiling; nevertheless the powder 
which has once been formed by means of muriatic or sulphuric acid, is not 
dissolved by boiling nitric acid, but only turned yellow. Acetic acid pro- 
duces no effect. Oxalic acid gives a white precipitate of oxalate of lime. 
Bichromate of potash and sulphuric acid produce no effect on a solution of 
xanthin, even on boiling. On adding caustic potash to the solution it turns 
brown, and on boiling a slight smell of ammonia is evolved. Lime and 
baryta water, acetate and basic acetate of lead, the acetates of alumina, iron 
and copper, nitrate of silver, corrosive sublimate, and a solution of glue, pro- 
duce no precipitate or effect whatever in a solution of xanthin. In fact it 
does not seem to be precipitated by any reagent whatever without undergoing 
decomposition. 
If a clear light yellow watery solution of xanthin be evaporated with the 
assistance of heat and in contact with the air, as on the sand-bath, to a 
syrup, and this syrup be again mixed with water and the solution again eva- 
porated, the process being several times repeated, the solution gradually be- 
comes dark brown, and at length a dark brown powder is deposited. ‘The 
brown solution now gives with acetate, or basic acetate of lead, a thick brown 
precipitate. The filtered liquid is yellow, and if the excess of lead be re- 
moved by sulphuretted hydrogen, the solution again gives, on evaporation 
over sulphuric acid, a colourless or light yellow syrup, which however, if re- 
dissolved and evaporated with the assistance of heat as before, again becomes 
dark brown, and deposits a dark brown powder. There can therefore be no © 
doubt that this brown powder is a product of the oxidation of xanthin, that 
xanthin is a species of extractive matter, and that the brown powder stands 
in the relation to it of an apothema. This brown powder has the following ~ 
properties :—When dry it is a dark brown mass, easily reduced to powder. It — 
is quite insoluble in boiling water and boiling alcohol. It burns without 
flame, leaving much ash. It is soluble in concentrated sulphuric acid with a 
dark brown colour, and is re-precipitated by water. Boiling dilute nitric — 
acid decomposes it with an evolution of nitrous acid, and changes it into a 
yellowish-red flocculent substance. Concentrated nitric acid on boiling de- : 
composes and dissolves it entirely. It dissolves in caustic and carbonated 
alkalies with a dark brown colour, and is re-precipitated by acids in light 
brown flocks. The ammoniacal solution gives brown precipitates with the 
x 
chlorides of barium and calcium, The dark green powder which is produced — 
8 
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