46 “On the Erythric Acid, €'e. 
that no turbidness results from the above solution of lead, nor 
any other of this metal; thus a colourless liquid of a pungent 
acid taste will be obtained. It reddens turnsole, but does not 
render lime-water turbid; united with potash, having acquired a 
sweet taste, it becomes insoluble in alechol, and in a word pos- 
sesses all those characters which belong to erythrat of potash 
spontaneously altered. 
42. Erythric acid also attacks metallic lead, making the for- 
mer boil on the latter’: the acid after some time reddens y and it 
is discovered by sulphuric acid, that it contains lead in solution. 
Other metallic Erythrats. 
43. Erythric acid agitated with red oxide of mercury becomes 
turbid, and much more so by the action of fire. In time no 
colour appears in this, the salt is deposited in the progress of 
evaporation, and the liquid abandons it copiously in cooling ; of 
the mercurial salt a very little remains in solution, and the pre- 
cipitate is then entirely insoluble in distilled water. 
.44, In asimilar manner the evythric acid acts with oxide of sil- 
ver. Boiled also on the flowers of zine,it dissolves the metal. with- 
out changing colour, aud becomes very turbid in cooling. Boiling 
it on the contrary over metallic zinc, it assumes a yellow colour 
on uniting with it. Potash at first produces a precipitate in this 
solution ; but afterwards on adding it, the whole dissolves, and 
takes a beautiful rose colour. 
45. Erythrie acid boiled over copper acquires a yellow colour 
without dissolving any. It unites however in the cold way with 
the brown oxide. The erythrat of copper has a green colour ; 
it crystallizes elegantly in the form of the plumage of feathers, 
gives a blue colour with ammonia, and, what is very singular, 
likewise yields a blue colour even with potash without ‘producing 
any precipitate. Thus, potash forms with the solutions of me- 
tallic erythrats combinations still soluble, which renders it pre- 
- sumable that a triple salt is formed. 
CoNncLUuSION. 
46. No one who considers the effects of nitrous on uric acid 
can see them without surprise at the multitude of products which 
are derived from them. The greater part of these, however, is 
the fruit more naturally peeuliar to other bodies; on the other 
hand, erythric acid is that which exclusively belongs to. the de- 
composition of uric acid; and hence is the more ‘valuable and 
eminent product. Erythric acid is a substance so singular for 
its physical changes, rather than for its chemical properties, that 
the lovers of the natural. sciences will willingly make it the object 
of their study. In these observations I only proposed to myself to 
recognise and account fot the principal phenomena which . 
thric 
