DETECTION OF LIME USED IN DAIRY PRODUCTS. 15 
EFFECT OF IMPURITIES IN THE SALT ON THE PERCENTAGE OF 
CALCIUM OXID IN THE SALT-FREE ASH. 
CALCIUM SULPHATE. 
The most usual impurity in dairy salt and the one present in 
greatest quantity is calcium sulphate. The amount of salt-free ash 
in butter will increase with the calcium content if salt containing 
calcium sulphate is used, but it will not increase in the same ratio. 
The calcium oxid percentage in calcium sulphate is 41, in the ashes 
of dairy products it averages about 22 per cent. This difference will 
cause an increase in the calcium oxid percentage in the salt-free ash, 
the amount of increase depending upon the quantity of salt used and 
the amount of impurity in it. 
Street 1 found in 21 samples of salt examined, from 0.30 to 1.23 
per cent of calcium sulphate and from to 0.35 per cent of calcium 
chlorid. Woll 2 found in domestic brands of dairy salt percentages 
of calcium sulphate ranging from 0.31 to 1.87 per cent and of calcium 
chlorid from 0.02 to 0.65. The maximum allowances for table or 
dairy salt that have been established by the Department of Agri- 
culture are: 1.4 per cent for calcium sulphate and 0.5 per cent for 
calcium chlorid plus magnesium chlorid. 3 
To ascertain the effect of impurities in the salt upon the per- 
centage of calcium oxid in the salt- free ash, a number of experiments 
were made. Four unsalted stock butters, A, B, C, and D, were used 
for this purpose. About 5 pounds of butter were melted and well 
shaken during solidification. Portions of 200 grams were withdrawn 
and melted in a bottle with 10 grams of salt of known composi- 
tion. The butter and salt were well mixed by shaking during 
solidification. The butter treated in this manner contained approxi- 
mately 4.75 per cent of salt. This is more salt than the average 
American creamery butter contains, but it was thought best to work 
with quantities higher than the average so that a certain amount of 
margin for variation might be provided. 
The methods employed in the analysis of butter thus treated were 
the same as those given on page 3. Figures for sulphur trioxid, 
calculated to calcium sulphate, are also included. In some cases the 
sulphate was determined by dissolving the ash of 40 grams of but- 
ter in dilute hydrochloric acid and then precipitating with barium 
chlorid. In other cases 100 grams of butter were melted and ex- 
tracted with 50 cc portions of warm water acidulated with hydro- 
1 Street, J. P. Thirteenth Report on Food Products. In Conn. Agr. Exp. Sta. Bien- 
nial Rpt., 1907-08, Pt. IX, p. 595. 
2 Woll, F. W. A Study of Dairy Salt. In Wis. Agr. Exp. Sta. Bui. 74, pp. 12-13, 
May, 1899. 
3 U. S. Dept. Agr., Office of the Secretary, Circ. 19, Standards of Purity for Food 
Products, p. 19. 
