PRELIMINARY AND MINOR PAPERS 
CRYSTALLIZATION OF CREAM OF TARTAR IN THE 
FRUIT OF GRAPES 
By William B. Alwood, 
Chief , Etiological Laboratory , Bureau of Chemistry 
During the chemical examinations made of the ripening fruit of grapes 
in the Enological Laboratory, Charlottesville, Va., the writer was led to 
conclude that the acid salt bitartrate of potassium was deposited from 
the juice in quantity sufficient to sensibly affect the analytical results. 
This led to the preparation of samples by the complete exhaustion of the 
soluble constituents of the berries, with results which supported the 
above conclusion. 
The question of the character and location of the crystals of cream of 
tartar in the berry presented itself as a matter of interest and possibly of 
practical importance. The literature available did not furnish specific 
information on this point. Babo and Mach, in their exhaustive treatise, 
give but one brief reference to the occurrence of this salt in crystals in the 
fruit. 1 
As soon as the fruit was well colored at Charlottesville in 1912 a series 
of microscopic examinations was undertaken to determine whether 
crystals of bitartrate of potassium occurred in the fruit. Portions of 
Concord grapes were prepared and examined daily until the fruit was 
ripe. Minute crystals varying much in shape and size were found in 
great abundance in the soft cells lying just beneath the skin of the fruit. 
Crystals were not present at any time in the pulp or compact portion of 
the flesh in which the seeds are contained. Like examinations of Con¬ 
cord and Catawba were carried on at Sandusky, Ohio, in September and 
October, 1912, and crystals of the same general type were found. 
The fact that many of the crystals found in the berries did not conform 
in type to crystals of the bitartrate prepared from pure cream of tartar 
made it doubtful as to whether potassium bitartrate was deposited or not. 
Therefore, the fruit was separated into portions for the purpose of a 
chemical examination covering this point. The tough pulp containing 
the seeds of 1,500 grams of ripe berries was separated from the hulls and 
soft peripheral layer of cells which adhere to the hulls. This layer con¬ 
tains the coloring matter. The hulls and pulp were then carefully pressed 
by hand and the juice of each recovered and held separately. This gave 
three portions: (1) The pressed hulls, (2) the juice recovered from the 
hulls, and (3) the juice recovered from the pulp. 
In preparing the sample all the juice possible was recovered from the 
sample of hulls and pulp; that is, they were entirely exhausted so far as 
crushing and pressing could accomplish this result. The pressed hulls 
were then carefully macerated in distilled water until the soluble organic 
matter was exhausted. These portions showed on analysis the results 
given in Table I. 
1 Babo, A. F., and Mach, E. Handbuch des Weinbaues und del Kellerwirtschaft. 
p. 16. Berlin, 1910. 
Aufl. 4, Bd. 2, 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
(513) 
Vol. I, No. 6 
Mar. 25,1914 
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