450 FOODS AND FOOD ADULTERANTS. 



etc., by dissolving them in a mixture of alcohol and ether, cooling the solutions, and 

 allowing the fats to crystallize out. He claims that he could distinguish the crystals 

 obtained from different fate in this way, and. gives illustrations made from drawings 

 of the various forms of crystals. The delineations are very crude and poor. 



In the famous "Chicago lard case"* microscopical methods were employed by ex- 

 perts for the defense to distinguish pure lard from lard adulterated with beef fat. 

 Dr. W. T. Belfield seems to have been the first in that trial to point out the differences 

 between crystals of these fats obtained from their solutions in ether or alcohol, and 

 his methods and conclusions were followed and confirmed by most of the scientific 

 experts employed by the defense. Dr. Belfield claimed to be able to recoguize in this 

 way as little as 10 per cent, of beef fat in lard, while some of the other gentlemen 

 thought that as low a proportion as 5 per cent, could be shown. Twelve photomicro- 

 graphs were submitted -by Dr. Belfield as part of his testimony, and are reproduced 

 in the report of the trial. They consist of crystals obtained from pure lard, both 

 steam and kettle rendered, pure tallow, lard mixed with 30, 20, and 10 per cent, of 

 beef tallow, and crystals from the three suspected samples of lard, "Fowler's" Nos. 

 1, 2, and 3. The reproduction is fairly good, but the amplification is not stated. 



In Part I of this Bulletin is presented a discussion of the microscopical appearances 

 of the various fats used in the adulteration of butter, especially the characters pre- 

 sented by them when viewed by polarized light, with photomicrographs prepared by 

 Messrs. Richards & Richardson.f These are intended especially to show the use of 

 the microscope with polarized light in distinguishing butter from its adulterants, the 

 former having, unless it has been melted and cooled or crystallized from solvents, no 

 crystalline structure, hence showing no refracting bodies when viewed by polarized 

 light, while the substitutes, involving as they do in their preparation previous melt- 

 ing and consequent crystallization, show a variegated field. Some of these photo- 

 micrographs represent crystals obtained from lard and beef fat by crystallization from 

 ether or alcohol, but the illumination by polarized light does not give the perfect de- 

 lineation of the shape of the individual crystals necessary for their differentiation. 



Examination of lards and lard substitutes icith the microscope. In the microscopical 

 work on the larger series of samples used in the present examination, and the investi- 

 gation of the efficiency of this test in distinguishing between lard and its substitutes, 



1 had the benefit of the advice and experience of Prof. S. P. Sharpless, one of the 

 chemists exployed in the Chicago trial, who has had occasion to examine microscop- 

 ically a large number of lards and lard substitutes in the course of an extensive com- 

 mercial experience. Most of the samples were examined by both of us, and our re- 

 sults agreed with very few exceptions. 1 subjected the entire series of samples to a 

 very careful examination, making several crystallizations in nearly every case, and 

 making photo-micrographs of the appearances found in a large number of the sam- 

 ples, selections from which are reproduced in the plates. 



Methods of procuring crystals for examination. The methods employed by the ex- 

 perts in the Chicago case, in these microscopical examinations, filed as part of their 

 testimony before the Board of Trade, are given on page. 



It will be seen that there was considerable diversity in the solvents used, the man- 

 ner of crystallization, and the method of preparing the crystals for examination. 



My method of procedure was similar to those given, in a general way. About 



2 to 5 g of the samples were taken, dissolved up in 10 to 20cc of ether in a test tube, the 

 operation being generally hastened by warming, the tube loosely stopped with cotton, 

 and allowed to stand over night at the ordinary temperature of the room. The proper 

 proportions of substance and solvent can not be laid down absolutely as they are de- 

 pendent upon so many conditions of temperature, solubility of the sample, etc. The 

 proportion giving a proper rate of crystallization, neither too rapid or too slow, can 



*McGeoch, Everingham & Co. vs. Fowler Brothers, published by Knight &Leouard. 

 Chicago, 1883. 

 t Pp. 34-40. 



