470 
Journal of Agricultural Research 
Vo . XXX, No. 5 
withdrawn without removing any of the 
crystals. The saturated alcoholic solu¬ 
tion as a rule was made up to a volume 
of 50 c. c., or diluted 5 times; the satur¬ 
ated petroleum ether solution was 
diluted 100 or 200 times, and the 
saturated ether solution was diluted 
1,000 times for the spectrophotometric 
determinations. In every case U. S. P. 
ether was used in making the dilutions, 
which were all made at room tempera¬ 
ture a few minutes before the -spec¬ 
trophotometric readings were taken in 
a 2 cm. cell. The scale on the spec¬ 
trophotometer was set so as to use the 
mercury line 435.8 m^, in which position 
readings were made. 
The quantity of pigment in the 
various solutions was determined at 
room temperature by means of a 
Konig-Martens spectrophotometer in 
the manner described in a previous 
paper (6 ). 
Experiments 3, 4, 5, 6, 7, and 8 of 
Table I were made in a slightly different 
way than 1 and 2. In these cases the 
solubility tests were made in 30 c. c. 
bottles placed inside a fruit jar which 
was closed tightly so that no water 
might enter. The jar and its con¬ 
tents were then mechanically revolved 
in the water bath for the time specified. 
In experiments 6, 7, and 8 the caro¬ 
tin crystals used were taken from the 
same preparation of carotin, the other 
experiments being on different samples. 
Table I .—Solubility of carotin at 25° C. 
in absolute alcohol 
Experi¬ 
ment 
No. 
Dilution 
Approxi¬ 
mate time 
in water 
bath 
Trans- 
mittancy 
Carotin 
per liter 
1 
Times 
5 
Hours 
3 
0. 2170 
Mgm. 
8.3 
2 
5 
12 
.1700 
9.6 
3 
5 
15 
.1920 
9.0 
4 
5 
20 
.0673 
14.8 
5 
5 
20 
.0572 
15.6 
6 
5 
48 
.0718 
14.3 
7 
5 
72 
.0371 
18.0 
8 
5 
90 
.0693 
14.6 
It appears that after 20 hours satu¬ 
ration was reached in the alcohol solu¬ 
tion; and, by averaging all of the fig¬ 
ures for the solubility at 20 to 90 hours 
In the water bath, the solubility for 
carotin in absolute alcohol is 15.5 mgm. 
per liter at 25° C. 
By averaging the results for 48, 72, 
;and 90 hours in Table II, it is found 
that about 626 mgm. of carotin dis¬ 
solved in one liter of petroleum ether 
at 25° C. 
Table II .—Solubility of carotin at 
25° C. in petroleum ether , B. P. 30° to 
50° 
Experi¬ 
ment 
No. 
Dilution 
Approxi¬ 
mate 
time in 
water 
bath 
i 
Trans- 
mittancy 
Carotin 
per liter 
i 
i 
Times 
100 
Hours 
3 
0.0610 
Mgm. 
! 305 
2 ! 
100 
15 
.0310 
382 
3 i 
100 
20 
. 0200^ 
428 
4 
200 
20 
.0890 
! 526 
5 1 
200 
48 
.0634 j 
604 
6 i 
200 
72 
.0724 
570 
7 J 
200 
90 
.0400 ! 
704 
The solubility in ether was obtained 
with difficulty, on account of the in¬ 
stability of carotin in ether solutions, 
as already mentioned. 
Table III shows the solubility of 
carotin in specially purified ether. At 
30 hours the equilibrium seemingly has 
become established and the average 
results show that approximately 1,005 
mgm. of carotin are soluble in a liter 
of ether at 25° C. 
Table HI .—Solubility of carotin at 
25° C . in absolute ether 
Sample 
No. 
Dilution 
Approxi¬ 
mate 
time in 
water 
bath 
Trans- 
mittancy 
Carotin 
per 
liter 
Times 
Hours 
Mgm . 
1 
1,000 
30 
0.402 
980 
2 
1,000 
46 
.377 
1,050 
3 
1,000 
54 
.398 
1,010 
4 
1,000 
90 
.402 
980 
Boiling ether was found by Will- 
statter ( 8 ) to dissolve about 1.11 gm. 
of carotin per liter and low-boiling 
petroleum ether on a reflux condenser 
to dissolve 0.66 gm. per liter, while 
he observed that carotin was very 
difficultly soluble in absolute alcohol. 
STABILITY OF CAROTIN IN 'SOLU¬ 
TION 
A small quantity of pure carotin 
was placed in each of three flasks; 
absolute alcohol was added to one, to 
another absdlute ether (not freshly dis¬ 
tilled), and to the third petroleum 
ether (30° to 50°). The solvents used 
were of the same grade as those em¬ 
ployed in the solubility tests above, 
except that the ether was taken directly 
from the container in which it came. 
