
Bol 
The direct examination with polarized light and aselenite 
plate showed prismatic colors in all of the adulterated but- 
ters, and a uniform tint in all of the genuine butters except 
No. 2, which appeared very much like the adulterated sam- 
ples. The crystals from all of the butters, adulterated as 
well as genuine, gave a well defined St. Andrews cross with 
polarized light. This was also the case with neutral lard 
(No. 14) in which the cross was sharply defined though quite 
small. No. 15 consisted of stearine from the oleo-oil fac- 
tories and showed no cross when examined by itself, but 
when combined with a small quantity of butter fat the 
crystals formed had the same appearance as those from 
pure butter. 
Tne method has also been quite unsatisfactory in trials 
made at the Station with butters whose character was 
known. Whether these results were due to a lack of skill 
or to imperfect knowledge in the details of the work, I do 
not know. The uncertain results of some skilled micros- 
—cop:sts, however, would indicate that the difficulty is in- 
herent in the method. It certainly is not simple, and is not 
calculated to supersede the chemical methods now in use. 
In the table presented below the column marked c. ¢. of 
tz NaOH indicates the amount of soda solution required to 
neutralize the fatty acids obtained from 2.5 gms. of butter 
fat by Reichert’s method. The average for pure butter is 
about 14 c.c., and any sample requiring less than 12.5 c¢. ¢. 
‘may be considered adulterated. 
The insoluble fatty acids were obtained by washing and 
weighing the portion left in the flask after distillation by 
Reichert’s method. No attempt was made to recover the 
small quantity which is carried over with the distillate. 
These numbers are therefore somewhat lower than the av- 
erage, but show in a satisfactory manner the adulterated 
samples, all of which gave over 90 per cent. ; 
It was supposed that there would be found a much wider 
difference between the melting points of the fats and the © 
insoluble acids derived from them, in the pure butters than 
in the adulterated ones. This was the’ case, although in 
numbers 12 and 13, both adulterated, the difference was 
nearly as great as in the pure butters. The melting points 
were taken, by the method described by Blythe, in a capil- 
lary tube open at both ends. The melted fat is drawn into 
one end of the tube and allowed to solidify. This end of 
the tube is immersed in a beaker of water the surface of 
- which must be at a higher level than the top of the fat, and 
the water warmed. The melting point is taken when the 
fat rises in the tube. The results are not very satisfactory, 
although quite close duplicates may be obtained. . 
