﻿180 Prof. R. Bunsen's Calorimetric Researches. 



with the atomic weight hitherto accepted. The calcium was 

 prepared by electrolysis from pure chloride of calcium. It 

 formed small pale golden-yellow globules of bright metallic 

 lustre, which speedily become grey on exposure to the air. 

 Before enclosing it in the glass vessel, it was scraped bright in 

 an atmosphere of dry carbonic acid. On testing it was found 

 to be nearly perfectly pure. From the specific heat found, it 

 may be concluded that the atomic weight hitherto accepted, 

 Ca=20, is correct, and must not be halved, as has become ne- 

 cessary in the case of the alkaline metals. 



By allotropic tin is meant that peculiar modification of the 

 metal which appears to be formed from ordinary tin exposed for 

 a length of time to very low temperatures. The piece used for 

 experiment was obtained from the large mass transformed during 

 an unusually long and severe winter, in which Fritsche observed 

 this remarkable allotropism, first described by him. The mass 

 consisted of an aggregation of angular stalks loosely coherent in 

 one direction, and crumbling by slight pressure. This tin, as I 

 convinced myself, is of a high degree of purity, is free from any 

 trace of arsenic or antimony, and dissolves entirely in trisulphide 

 of potassium without any residue of metallic sulphides. The 

 little stalks of which it is composed are not brittle, but ductile 

 like ordinary tin. The specimen of ordinary tin examined was 

 obtained by melting the allotropic metal. Both modifications 

 possess nearly the same specific gravity. 



The indium used appeared perfectly free from tin, cadmium, 

 and iron. After oxidation by nitric acid and evaporation with 

 sulphuric acid, it left no trace of sulphate of lead when dissolved 

 in alcohol. 1*0592 grm. of the metal was dissolved without loss 

 in nitric acid, and yielded on evaporation and ignition 1*2825 

 grm. oxide of indium. If we regard the latter, according to the 

 hitherto accepted view, as consisting of equal atoms, the value of 

 the atom of indium from this determination is 



In = 37*92; 



which figure agrees very nearly with Winkler's determination, 



In = 37-81. 



This atomic weight, multiplied by the specific heat s C) gives for the 

 atomic heat of indium the value 



s c In = 2*13, 



which does not agree with the other ones. Therefore the hypo- 

 thesis that the formula of oxide of indium is InO appears no 

 longer tenable. If the atomic weight be taken as once and a half 

 the above, In = 56-7; 



