154 Canadian Record of Science. 



Dr. Lepenau's Lepto meter (described in Schoedler's " Unter- 

 suchungen der Fette, u.s.w.", Leipzig, 1890, pp. 68-69), 

 using the same oil in both of the cups. In spite of very 

 careful workmanship, this instrument is so complicated 

 that exact results are all but impossible with it ; and the 

 interchangeable nozzles, even if made strictly alike, will 

 give different rates of delivery unless, in adjusting them, 

 they be placed so that the planes in which they are bent 

 are made absolutely parallel; a condition very difficult to 

 fulfil in working with the instrument. 



At the best, the Leptometer has no advantage over the 

 simple apparatus first described, since it desiderates the 

 employment of a standard sample of oil. 



The only instrument claiming to do away with the 

 necessity of a standard sample, with which I am acquainted, 

 is Redwood's Viscometer, and my experience with it has 

 been unsatisfactory and disappointing. A full description 

 of the instrument will be found in Allen's u Commercial 

 Organic Analysis," vol. IL, pp. 198, 199. 



In a series of nine experiments, I got results at 200° F., 

 varying from 114 sec. to 155 sec, and no two alike, (50 cc. 

 of oil used.) At 250° F., the readings varied from 87 sec. 

 to 99 sec, and in all these trials the utmost care was taken 

 to secure uniform conditions. On considering the construc- 

 tion of the instrument, one finds many things which serve 

 to explain these very discrepant results. The inner cup 

 only contains 85 cc of oil at the beginning of the test. 

 This oil is in contact below with a thick plate of copper, 

 the oil on one side of this plate being at a temperature of 

 200° F. or 250° F., while the air of the laboratory, on the 

 other side of the plate, is at 60° or TO . Of course a very 

 rapid lowering of the temperature of the oil results. Fur- 

 ther, the upper surface of the oil is in contact with the air 

 directly, and is losing heat rapidly throughout the time of 

 the experiment, and this in a varying degree, since every 

 current of air in the laboratory affects it. The agate 

 tubulure is imbedded in the copper bottom of the cup, and 

 its temperature can never be that of the oil in the middle 



