Mar. 1, 1925 
473 
Physical and Chemical Properties of Carotin 
concentrating to about 250 c. c., a 
stronger suction is applied so as to 
evaporate the petroleum ether and 
cool the solution in order that more of 
the carotin will crystallize; during this 
evaporation the flask is removed from 
the water bath to cool the solution. 
Or, after concentrating to 250 c. c., the 
concentrated carotin solution may be 
placed in an ice chest. In two or three 
days most of the carotin will have 
crystallized from the solution. The 
crystals are then filtered off. 
After separating the gold, shimmer¬ 
ing mass from the mother liquor by fil¬ 
tration, the crystals are dissolved on the 
same filter in the least possible quan¬ 
tity of chloroform or carbon disulphide, 
from which they are precipitated by 
shaking vigorously with small portions 
(50 to 100 c. c. in all) of absolute al¬ 
cohol. Greatly reduced pressure may 
be used here, which will cause the 
chloroform or carbon disulphide to 
evaporate and cool the solution. Both 
the cooling and the evaporation of the 
solvent aid in crystal formation and 
cause a larger yield. After about one 
hour the crystals are filtered off either 
on a filter paper or a linen cloth; the 
flask in which the precipitation took 
place is rinsed with low-boiling petro¬ 
leum ether (25 to 50 c. c.), and this is 
used to wash the crystals which are on 
the filter paper or cloth in the Buchner 
funnel. This washing will dissolve 
most of the remaining fats and waxes. 
The crystals are washed again with 
low-boiling petroleum ether and suc¬ 
tion is applied till they are free of this 
solvent. Willstatter washes here with 
a half-and-half mixture of alcohol and 
petroleum ether; this mixture has the 
advantage that it does not dissolve as 
much of the crystals and the disad¬ 
vantage that it does not dissolve the 
impurities as well as pure petroleum 
ether. 
To avoid the possibility of the caro¬ 
tin crystals containing alcohol of 
crystallization (7) they are recrystal¬ 
lized by dissolving in just enough 
chloroform or carbon disulphide to 
effect solution and then adding petro¬ 
leum ether (30° to 60°) and evaporating 
to about 25 c. c. or less. ' The crystals 
are collected on a hardened filter paper 
and washed two or three times with 
10 to 15 c. c. portions of low-boiling 
petroleum ether. Any traces of fats, 
waxes, or oils should be removed by 
this last precipitation and final wash¬ 
ing with petroleum ether. The pure 
pigment thus obtained is dried for 15 
to 30 minutes in a good vacuum desic¬ 
cator. The melting point is deter¬ 
mined and, if found satisfactory (174°), 
the samples desired are rapidly 
weighed, placed in glass tubes filled 
with CO 2 , sealed or dissolved for use, 
and the remaining crystals stored im¬ 
mediately, as described below. 
Carotin crystals in mass are col¬ 
ored dark copper-red. When viewed 
through the microscope they have an 
orange-red color (3). The color and 
crystal form are illustrated by Escher 
{2) and the crystal form by Willstatter 
and Stoll (8). Carotin nearly always 
crystallizes in plates or leaves which 
often are rhombic or quadratic, and 
rarely does it crystallize in needles. 
The form and the size of the crystals 
vary with the solvent, the amount 
of the impurities in the solution, the 
temperature, and the time allowed for 
crystallization. 
Very dilute solutions of carotin in 
alcohol, ether, or petroleum ether are 
yellow, more concentrated ones are 
deep orange, and very concentrated 
ones are deep red, except in the case of 
alcohol where the saturated solution is 
yellow. A weak solution of carbon 
disulphide is pink to red, whereas the 
more concentrated ones are red, dark 
red to almost black. 
Escher (2) has obtained 125 gm. 
from 5,000 kgm. or 1 gm., of carotin 
from 40 kgm., (equivalent to 0.56 
gms. per bushel) of fresh carrots, which 
is perhaps the best yield reported in 
the literature. On a small scale, 
Escher obtained from carrots which he 
himself dried, carotin at the rate of 
0.10 gm. per kgm. of fresh carrots 
(equivalent to 2.27 gm. per bushel). 
He determined colorimetrically that 
carrots contained as much as 0.023 per 
cent of their fresh weight as carotin, or 
approximately 5.22 gm. per bushel, 
whereas the same variety when dry 
contained 0.013 per cent (based on 
fresh weight) of carotin or 2.95 gm. 
per bushel. Hence, there was a loss 
of 43.5 per cent of the carotin during 
the drying process. 
In this investigation, 1 bushel (50 
pounds) of fresh carrots contains from 
1.68 to 3.46 gm. of coloring matter 
estimated colorimetrically as carotin. 
The same carrots when dried and 
ground in a ball mill ready for ex¬ 
traction contained respectively 1.41 to 
2.81 gm. of carotin (based on a bushel 
of fresh carrots). From the bushel of 
carrots which contained 2.81 gm. of 
carotin when dry, 1.13 gm. of pure 
carotin, crystallized from petroleum 
ether and having a melting point of 
174° C., were obtained. The loss in 
drying, 16.1 and 18.8 per cent, re¬ 
spectively, is probably explained by 
the manner of slicing the carrots. 
