DAIRY PRODUCTS. 39 



A careful study of these illustrations will show that the microscope 

 and polarized light are most valuable and reasonably certain means 

 whereby a qualitative examination of butters can be made. The ap- 

 proximate amount of added fat can only be determined by a chemical 

 analysis of the suspected sample, taken in connection with some of its 

 further physical characteristics. 



I have given above all the really valuable points heretofore estab- 

 lished in respect of the use of polarized light in butter and fat analyses. 1 



The use of the microscope in butter examinations has not commanded 

 as much attention among analysts as its merits deserve. Sell says : 2 



Though investigations have shown that the differences in structure under the mi- 

 croscope are not in all cases sufficiently characteristic to determine a sharp distinc- 

 tion between two different fats, yet it must bo admitted that the microscopic exami- 

 nation is able to prove the presence of foreign fats at the moment it succeeds iu es- 

 tablishing the presence of molecular tissues in animal or vegetable parasites. 



Leudtner and Hilger say : 3 



The use of the microscope in the examination of fats requires a still further devel- 

 opment before it can become generally applicable. 



Having written to the editor of the Analyst for some information on 

 the subject of the use of the microscopic methods in England, he re- 

 plied: "The whole subject has been studied over and there is nothing 

 in it." 



Dr. S. M. Babcock, chemist of the New York Experimental Station, 

 says : 4 



At the time these butters were received there was considerable controversy regard- 

 ing the efficiency of Dr. Taylor's method for the detection of adulterations in butter 

 by means of the microscope. An excellent opportunity was olfered in these samples 

 for testing this method in an impartial manner, and a microscopical examination 

 of them was made before the nature of the butters was revealed by other tests. 

 The butters were examined directly with polarized light and a seleuite plate, and 

 afterwards the crystals from the melted butters wore examined in the same way for 

 the " Saint Andrew's cross." 



The direct examination with polarized light and a solenito plate showed prismatic 

 colors in all of the adulterated butters, and a uniform tint in all of the genuine but- 

 ters, ox cept No. 2, which appeared very much like the adulterated samples. The 

 crystals from all of the butters, adulterated as well as genuine, gave a well-defined 

 Saint Andrew's 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 stcarino from the olco-oil factories, 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. 



The method has also been quite unsatisfactory in trials made at the station with 

 butters whose character was known. Whether these results were duo to a lack of 

 skill or to imperfect knowledge in the details of the work I do not know. The 



1 Notices of minor importance on the same subject can be fouud in Chem, News, 

 vol. 4, pp. 230, 283, 309, 322 ; Zeit. Anal. Chem., 1872, p. 334 ; Jonrn. Royal Microscop- 

 ical Society, 1878, p. 378; American Quarterly Microscopical Journal, 1878, p. 294; 

 American Journal of Microscopy, October, 1878; Bied. Ceutralblatt, 1879, pp. 861-865; 

 1882, p. 345; 1882, p. 49; Amor. Chemist, vol. 2, p. 428. 



3 Op. cit., p. 503. 



3 Ver. Bay. Vortreter d. Angewand. Chem., p. 222. 



Fifth Ann. Rept. Bd. Control N. Y. Exp. Sta., pp. 330, 331. 



