PROCEEDINGS OP THE POLYTECHNIC ASSOCIATION. "^ 595 



centimeters of the oil to be tested, are intrQduced through the tabulature 

 of the retort, which should not be filled to more than one-third of its 

 capacity. A thermometer (Centigrade) is inserted into the tabulature of 

 the retort and adjusted so as to prevent it from touching the liquid. The 

 distillation of the liquid is now carried on by means of a gas-burner or an 

 alcohol lamp. If, for example, we wish to separate a mixture of crude oil, 

 1st, into oils distilling over lOO'^C. or 212° Fah; 2d, at from 100^ to 120^; 

 3d, from 120° to 140°; 4th, from 140° to 160«; 5th, from 160° to 180« (the 

 last term corresponding with 356° Fah); the mode of operation is to slide 

 the first graduated cylinder under the outlets of the retort, which will catch 

 all the oil condensed from the distillation at the first degree of temperature 

 mentioned, when the second cylinder is placed under the outlet to receive 

 the distillation at the second temperature required; thus the remaining 

 three vials are passed under the outlet. The oils thus collected being con- 

 densed in a uniform manner by cold water, will be of the same temperature, 

 and the volume in cubic centimeters in each cylinder will represent the 

 percentage of each oil contained in the mixture. ^' 



Mr. Garvey inquired if it was well established that petroleum is a mix- 

 ture of oils that can be separated at different boiling points — his own expe- 

 riments showed that very slight variation in temperature gave off" a different 

 oil, which on being again heated, passed into vapor at a lower temperature. 



Dr. Parmelee remarked that he used about 2,000 gallons of benzine per 

 week, having a sp. gr. of from *10^ to 80** Baume, and found it very difficult 

 to get it entirely free from naphtha by heat. Petroleum dealers have no 

 other means of estimating the different qualities of oil than the heat test. 

 Still there is no dividing line between the oils — they can be obtained at 

 almost any specific gravity between certain limits. 



The Chairman read his usual summary of scientific news, commencing 

 with a subject bearing upon the one just discussed. 



The Boiling Point as a Test. - 



The boiling point is not always a test of purity, according to a report to 

 the French Academy by M. Allnard, of experiments, mixtures of two liquids, 

 which mutually dissolve each ether in all proportions. Having discovered 

 that ether dissolved with 1-1 0th its weight of sulphide of carbon, boiled at 

 the same temperature with ether, Allnard made similar observations on a 

 mixture of alcohol and sulphide of carbon, also on mixture of alcohol and 

 ether. He admits that to determine the purity of a liquid recourse must 

 be had to M. Regnault's method of determining the elastic force of its 

 vapor. The presence of any substance added either to alcohol or sulphide 

 of carbon to the amount of 1,000th part can thus be detected. 



A New Disease. 



It is now admitted by medical authorities that anew disease is added to 

 the catalogue of human ills. Isolated cases of it in Europe have from time 

 to time been reported, but a communicatioafrom Dr. Milller, of Homberg, 

 in TJie London Lancet, contains an account of its propagation as an epi- 

 demic in Hettstacdt, a small town of five or six thousand inhabitants iu 



