Electro-deposited Antimony. 457 



ing to the amount to be discharged in relation to the amount of 

 cooUng influences present. 



The sjiecific heat of the unchanged metal was found to be 

 = 0"0G3r2 ; and of the same specimens, after being (/radually dis- 

 charged, the s])ecific heat was not sensibly different. But the spe- 

 cific heat of the substance, after sudden discharge, was found to 

 bc=0-05-13. 



The total amount of heat evolved by the substance during its 

 change was sufficient to raise the temperature of its own weight of 

 ordinary antimony (sp. heat=0*0508) about 650° J'ahr. 



The evolution of vapour which generally occurs during the change 

 is a result of the molecular heat acting upon the terchloride of anti- 

 mony contained in the substance. It occurs when a sufficient tem- 

 perature is produced either by internal or external causes, and does 

 not occur when the molecular discharge is gradual and the tempe- 

 rature is not sufficiently raised ; in such cases the weight of the sub- 

 stance remains unaltered. 



The substance, as usually produced from ordinary muriate of anti- 

 mony, or from a mixture of that substance and tartar-emetic, contains 

 small quantities of nearly all the ingredients and impurities of the 

 depositing liquid. 



The pure substance deposited Tipon sheets of platinum, in a solu- 

 tion of pure hydrochloric acid three-fourths saturated with pure 

 oxide of antimony, with an anode of pure antimony, exhibited uo 

 material difference in properties from the less pure variety. 



Two analyses of the inire unchanged substance gave the following 

 per-centages : — 



No. 1. 



Sb 93-3G 



SbCP ... 5-98 

 IICl 0-4G 



:G-41 



99-80 



A trace of water contained in them was not estimated. 



Solvents removed the chloride of antimony from the powdered sub- 

 stance much more readily after the thermic discharge than before it. 



Differences of physical appearance were detected in the changed 

 and unchanged substance in the state of powder under a microscope ; 

 the surfaces of the latter were smooth and brilliant, whilst those of 

 the former were r/ramdar and less briglit. No mechanical mixture 

 could be detected in the changed powder. 



From the various experiments detailed in the paper, it appears that 

 the substance in question is a feeble chemical comi)ound of antimony 

 and acid hydrochlorate of terchloride of antimony, apparently in 

 variable proportions, decomposable by heat, and that the change 

 observed in it, in cases oi yradual discharge, consists of a molecular 

 alteration, attended by weakened chemical affinity, and by evolution 

 of lieat ; but in cases of sudden discharge the evolved heat produces 

 a partial chemical decomposition, wliich is of greater or less extent, 

 according to the temperature accjuired. 



