DETECTION" OF LIME USED IN DAIEY PRODUCTS. 



17 



doubt to the manufacturer, it is not thought to be of any serious 

 consequence. 



Table 14 also shows that relatively high percentages of salt, 

 contaminated to a considerable degree, must be added before the 

 percentage of calcium oxid in the salt-free ash of butter made from 

 unneutralized cream will exceed 25, the tentative maximum limit. 

 If only 2.5 per cent of salt, the average quantity present in American 

 butter, is added, the salt may contain about 2 per cent of calcium sul- 

 phate before the limit is reached. Furthermore, a correction for cal- 

 cium sulphate in the salt can be applied by determining the sulphate 

 in the butter. The sulphate found is calculated to calcium sulphate 

 and this figure subtracted from the salt-free ash. The equivalent 

 amount of calcium oxid is subtracted from the total calcium oxid, 

 and the quotient of these corrected figures gives the actual per- 

 centage of calcium oxid in the salt-free ash. The determination of 

 the sulphate in the acidulated water extract is preferable to the ash- 

 ing method, as the results are higher owing to the well-known action 

 of phosphorus pentoxid in driving out sulphur trioxid unless suffi- 

 cient alkali is present. This action is especially strong in sample C, 

 because of its higher ash and consequently higher phosphorus pen- 

 toxid content. . It is possible that better results would be obtained by 

 the ashing process if sodium carbonate were first added, but since the 

 extracting process is just as quick, it appears to be preferable. The 

 amount of sulphates in the ash of unsalted butter or butter salted 

 with chemically pure salt, derived from the sulphur of the casein, 

 is so slight as to be negligible. In the extract method it would be 

 removed by the protein precipitant. 



CALCIUM CHLORID. 



Wlien salt is contaminated with calcium chlorid the action is 

 somewhat different. The calcium chlorid does not increase the 

 salt-free ash because it is almost equivalent to the two sodium 

 chlorid molecules calculated from the silver chlorid precipitate. 

 Therefore, the calcium oxid is increased without corresponding in- 

 crease in the salt-free ash, causing an increase in the percentage 

 of calcium oxid jn the salt-free ash. With about 5 per cent of 

 salt in the butter it requires an impurity in the salt of approximately 

 0.4 per cent calcium chlorid before the percentage of calcium oxid in 

 the salt-free ash of the butter will reach the limit of 25. Salt to the 

 amount of 2.5 per cent, when added to butter, may contain about 

 0.65 per cent of calcium chlorid, the maximum amount in dairy salt 

 as found by WoU,^ without causing errors in interpretation. No 

 correction for calcium chlorid can be applied. 



iWoU, F. W. A Study of Dairy Salt. Wis. Agr. Exp. Sta. Bui. 74, p. 13, May, 1899. 



