LARD AND LAKD ADULTERATIONS. 445 



Manipulation. Fifty cc of the fat or oil to be examined are placed in 

 the test tube and warmed or cooled, as the case may be, until the tem- 

 perature is the one required for the beginning of the experiment, say 35; 

 10 cc of the strongest sulphuric acid at the same temperature are placed 

 in the funnel, the stopper being firmly fixed in its place; the test tube 

 containing the oil is placed in a non-conducting receptacle; the wooden 

 cylinder lined with cork, used in sending glass bottles by mail, I have 

 found to be convenient for this purpose. A glass rod which fits loosely 

 in the stopper, so as to be moved rapidly up and down, is held by the 

 right hand of the operator; with his left hand he opens the glass stop- 

 cock of the funnel and allows the sulphuric acid to flow in upon the oil. 

 The glass stirring-rod is now moved rapidly up and down for about 20 

 seconds, thus securing a thorough mixture of the oil and acid. The 

 mercury rises rapidly in the thermometer and after two or three minutes 

 reaches a maximum, and then, after two or three minutes more, begins 

 to descend. The reading is made at the maximum point reached by the 

 mercury. With pure cotton oil, linseed oil, and some other substances 

 the rise of temperature is so great as to produce ebullition in the mass, 

 causing it to foam up and fill the tube. To avoid this smaller quantities 

 of acid should be used or the oil in question be diluted with a less 

 thermogenic one, so that the maximum temperature may not be high 

 enough to produce the effect noted. 



I have thought that the value of this method of work might be in- 

 creased by measuring the total temperature produced in mixing given 

 quantities of fet and sulphuric acid, and hope soon to have a calorimeter 

 constructed suitable for this purpose. 



Experiments made with the apparatus described above in regard to 

 the influence of the initial temperature have shown that a difference of 

 10 in the initial temperature would cause a difference of from 2 to 3 

 in the maximum temperature reached during the operation. 



Prof. C. E. Munroe, of Newport, has made extensive experiments on 

 the rise of temperature produced by the mixture of oils with sulphuric 

 acid. He has published some of the results of his work in volume 10 

 of the Eeports of the American Public Health Association.* 



In a manuscript communication from the author under date of July 

 20, 1888, Professor Munroe makes the following additional observations 

 upon his method and results : 



I first sought speed in mixing, using a turn-table upon which the vessel was put, 

 or mechanical stirrer placed in the vessel or shakers, etc., but while using Maumend's 

 proportions there -were discrepancies I could not explain. So then I varied the pro- 

 portion until -when I reached 20 cc of oil to 25 cc of H 2 SO 4 (sp. pr. 1.83) I easily got 

 concurrent results. I had the oil and acid and vessels all at the same initial tem- 

 perature. The oil was run into a beaker glass of 100 cc capacity, a delicate ther- 

 mometer was inserted and initial temperature marked and compared with thermom- 

 eter hanging beside burette containing oil and acid. Then acid -vas run in and the 



* Volume 10, American Public Health Association, reprints for the author an article 

 entitled " The Use of Cotton-Seed Oil as a Food and for Medicinal Purposes." 



