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XXXVII. On the Expansion of some Solid Bodies by Heat. 

 By Hermann Kopp*. 



THE method of experiment adopted by Professor Kopp in 

 his laborious and valuable investigation is to ascertain the 

 specific gravities of a body when immersed in fluids of various 

 temperatures, and thence, by means of the known expansion of 

 the fluid, to determine the cubic expansion of the body. A flask 

 was taken furnished with a carefully ground glass stopper ; and 

 the first point to be ascertained was, " What weight of water, 

 freed from air, and at different temperatures, was the flask able 

 to contain V For low temperatures, the flask and its contained 

 water were placed in a large vessel filled with the same fluid, 

 the temperature of which was shown by two thermometers im- 

 mersed in it. When it was certain that the flask had assumed 

 the temperature of the surrounding water, the stopper (which 

 was preserved at the same temperature) was set on, the flask 

 dried, and then carefully weighed. For temperatures of 40° or 

 50° C, the flask was immersed in a large beaker filled with 

 water, which again was immersed in a second larger beaker, 

 also fidl of water ; the latter was heated, and after some time 

 the water surrounding the flask acquired a uniform tempera- 

 ture of the required height; the glass stopper, which up to 

 this time had been preserved in water of the same temperature, 

 was now set on, the flask removed, dried, and weighed as before. 

 When the quantity of boiling water held by the flask was to be 

 ascertained, the latter was properly fixed in the neck of a large 

 bolt-head, in which a quantity of water was kept violently boiling. 

 The flask was here surrounded by steam, and precautions were 

 taken to prevent any inconvenient loss of heat by radiation or by 

 contact with the surrounding air. 



Having ascertained the amount of water embraced by the flask 

 at numerous temperatures, a proceeding exactly similar was fol- 

 lowed to ascertain the specific gravity of the substance. The 

 flask with the substance alone was first weighed ; the flask was 

 then filled with water, the air completely expelled by boiling, 

 and then the weight of the known quantity of solid substance, 

 plus the weight of the water necessary to fill the flask at various 

 temperatures, was ascertained. 



Suppose the weight of the flask of water at the temperature 

 t° to be W, the weight of the solid substance to be examined to 

 be P, and the weight of the water and substance which together 

 filled the flask at t° to be S, then we have 



P_=D 



W-(S-P) " 



* Ann. der Chern. und Phartn., vol. Ixxxi. No. 1. p. 1-6". 



