VARIATIONS OF SPP:CIFIC GRAVITY." 



By (}. W. A. Kahlbaum. 



In coiinootion Avith researclies on the distillation of metals, and 

 while seeking- to fix the specific gravity of the pure metals emphwed, 

 I was led to make a thorough study of the subject of specific gravity 

 measurements.* The grounds which led me to bestow so much atten- 

 tion on this subject apparently so threadl)are are these: First, the 

 exact measurement of specific gravity, particularly for solid bodies, 

 is an extremely difficult piece of work, which can be successfully 

 accomplished only by attending to certain not unimportant pre- 

 cautionary measures; and, second, the specific gravity to be deter- 

 mined is to be regarded rather as the expression of particular prop- 

 erties of the individual s])ecimGn examined than as a general property 

 of all yolids of the same kind. 



This latter statement may be illustrated by the following determi- 

 nations made on a -small block of the purest Norwegian converter 

 copper refinings, for which chemical analysis yielded 09.92 per cent 

 copper, 0.02 per cent siher, 0.04 per cent nickel, and 0.02 per cent iron. 

 Three small bars, G mm. in diameter and 45 mm. in length, were pre- 

 pared, containing about 1.25 cm'' each, and their specific gravity was 

 determined within a mean error of O.OOIG, as follows: I, 8.4412: II, 

 8.092(); 111,8.1297. 



Thus it appears that three cylinders, turned from a single snuill 

 block of copper, showed a variation of specific gravity through a 

 range of 0.2()29, or over 3^ per cent of the whole specific gravity. 

 Inasmuch as this was cast copper it was easy to explain the cause of 

 the variation, for probably there were faults or blowholes in the 

 casting. But the interesting and natural ([uestion arose. Where and 

 when do such faults cease entirely? 



With another cylinder of the same copper, weighing 79 grams, I 

 made careful measurements by the volumetric method, depending 



o Translated, by permission, from Annalan der Physik. Leipzig, No. 8, 1904. 

 b(i. W. A. K.ililliauin, Zoitscli. f. anorjr. Chem. 20. j.p. 197-213, 1902. 



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