THE VOLATILE PART OF PLANTS. 97 
to illustrate the peculiarities of this substance, and to ex- 
hibit the deportment of the albuminoids generally towards 
the above-named reagents. 
Exp. 42.—Beat or whip the white of an egg so as to destroy the deli- 
cate transparent membrane in the cells of which the albumin is held, 
and agitate a portion of it with water; observe that it dissolves readily in 
the latter. 
Exp. 43.—Heat a part of the undiluted white of egg in a tube or cup 
at 165° F.; it becomes opaque, white, and solid, (coagulates) and is convert- 
ed into the insoluble modification. A higher heat is needful to coagulate 
solutions of albumin, in proportion as they are diluted with water. 
Exp. 44.—Add strong alcohol to a portion of the solution of albumin 
of Exp. 42. It produces coagulation. 
Exp. 45.—Observe that albumin is coagulated by dilute acids upplied 
in small quantity, especi:lly by nitrie acid. 
Exp. 46.—Put a little albumin, either soluble or coagulated, into each 
of four test tubes. To one, add solution of iodine; to a second, strong 
ehlorhydric acid; to a third, nitric acid; and to the last, nitrate of 
mercury. Observe the characteristic colorations that appear immedi- 
ately, or after a time, as described above. In the last three cases the 
reaction is hastened by a gentle heat. 
Albumin occurs in the soluble form in the blood, and in 
all the liquids of the healthy animal body except the urine. 
In some cases its characters are slightly different from 
those of egg-albumin. The albumin of the blood, which 
‘may be separated by heating blood-serum (the clear 
yellow liquid that floats above the clot), contains a little 
less sulphur than coagulated egg-albumin. In the erystal- 
line lens of the eye, and in the blood corpuscles, the al- 
bumin has again slightly different characters, and has been 
termed globulin. Under certain conditions the blood of 
animals yields a substance known as hemoglobin, which, 
while having nearly the composition and many of the 
properties of albumin, commonly requires a much larger 
proportion of water for solution, and forms distinct crys- 
tals of a transparent red color. 
Vegetable Albumin.—In the juices of all plants is found 
4 minute quantity of a substance which agrees in nearly 
all respects with animal albumin, and is hence termed 
5 
