A Manual of the Chemistry of the Carbon Compounds

402' TBE OftEMISTMY Off
aspartic acid, levfiine, kucimide, btomanU, and amidotribromobeiizoic
acid.
"When heated with hydrochloric acid and stannous chloride, they
undergo a very simple decomposition, being resolved into ammonia,
aspartic acid, glutamtie acid, leminc and tyrosine.
Senim-Albumin exists in the blood of vertebrate animals, in chyle
and lymph, &c, and in small quantity also in milk. In diseases of
the kidneys it appears in considerable quantity in urine.
It is prepared by diluting blood-serum, with a little water, and
adding carefully acetic acid, to precipitate other proteids. The
filtrate is evaporated at a temperature not exceeding 40°, and thus
an amorphous mass is obtained, giving with cold water a clear
solution.
"When a solution of albumin is heated to 72° it coagulates to a
compact mass. Hie presence of acids or salts raises the temperature
of coagulation, whilst alkalis lower it. On adding hydrochloric acid
to a solution of albumin, a precipitate is formed which dissolves in an
excess of the acid.
Egg-Albumin is contained in the white of tlie egg, and differs from
serum-albumin by being almost insoluble in nitric acid, and being
gradually precipitated when its solution is shaken with ether. It is
also precipitated by hydrochloric acid, but dissolves only with difficulty
in an excess.
The two albumins possess right-handed rotatory power; that of
egg-albumin being less powerful than that of the other.
Vegetable Albumin exists in almost every vegetable juice, and
coagulates when its solution is heated; it has not been obtained pure,
and is therefore only imperfectly known.
Casein is found iu milk and the yolk of eggs, and obtained in a
pure state by adding dilute sulphuric acid to milk, from which the
cream lias been removed, and digesting the curdy precipitate with
water and lead carbonate. The solution thus formed is treated with
hydrogen sulphide, and the filtrate evaporated at a low temperature.
Casein is insoluble in pure water, but dissolves if a trace of an
acid or alkali be present. This solution is precipitated byjacids, a
compound of casein with the acid being formed. A solution of casein
is also precipitated by adding some "rennet" to it, aud heating to
about 53°, but not by heat alone.
Vegetable Casein or Zegnmin exists in many seeds such as peas,
beans, vetches, &c, from which it is obtained by softening them with
warm water, and triturating them into a pulp, which is pressed
through a sieve. On standing, the liquid deposits starch; the clear
solution is then decanted and precipitated with acetic acid. Legumin
has great resemblance with milk-casein.
Conghtiv. is a proteid existing in almonds and lupine-seeds. It is
a white powder, which is sparingly solnble in water, and freely in
dilute alkalis and in acetic acid. Acids precipitate it from the
alkaline solution as a very adhesive mass, drying up to a glassy