A Manual of the Chemistry of the Carbon Compounds

THS CARBON COMPOUNDS. 491
ALBXJMIHOIDS OR PROTEID8,
These important compounds form the chief parts of the solid constituents
of blood, muscles, glands, and other organs, and occur
also in plants, principally in the seeds. Their constitution is completely
hidden in darkness; from the results of their ultimate
analysis no formula can be calculated, on account of their high
molecular weight, which, however, is not known, as they do not form
definite compounds with other bodies, and are neither volatile nor
crystalline. It is not even known whether some of them are pure
compounds or only mixtures. They have all a very similar composition,
and contain in 100 parts :—
52—54 parts of Carbon
7—7*3 „ Hydrogen
13—16 „ Nitrogen
21—26 „ Oxygen
1—1-6 „ Sulphur
They also always contain a small quantity of calcium phosphate.
Most proteids exist in a soluble and an insoluble modification.
An aqueous. solution of the soluble bodies dries up to a gum-like
mass, and is precipitated by different agents, the insoluble modification
separating out as amorphous white flakes, or curds.
They all dissolve in glacial acetic acid, in a strong solution of
phosphoric acid, in concentrated hydrochloric acid, and in alkalis.
When the acetic acid solution is diluted with much water it yields
precipitates with potassium fcrrocyanide, ferrioyanide and platinocyanide.
On boiling them with hydrochloride acid in contact with
the air, the solution assumes a blue colour, changing gradually into
violet and brown. When then 1 alkaline solution is boiled, a part of
the sulphur is eliminated is the form of an alkaline sulphide. On.
heating a proteid with a solution of niereurous nitrate containing
nitrous acid, it assumes ft fine red colour, and a similar colour is produced
by the joint action of a solution of sugar and sulphuric
acid.
When exposed to the air in the moist state, they rapidly undergo
putrefaction, the products consisting of ammonia, ammonium sulphide,
carbon dioxide, volatile fatly acids, lactic add, amines, leuciw and
tyro/tine.
The two latter bodies are also produced by boiling a proteid with
dilute sulphuric acid.
Chromic acid-solution oxidizes them to fatly aldehydes, acids and
nitrites and benzahhliyde aud henzoic and.
On. heating them with water ami bromine under pressure they are
rpsolved intn anrlinn rliorlrk, hvemoform. bromacctic and. oxalic acid,