by Weight and by Volume. 305 



recently precipitated, were readily dissolved by chloride of ammo- 

 nium. The same remark applies tp the solvent action of chloride 

 of calcium. 



For the volumetric determination of bismuth no method has 

 hitherto been proposed. To supply the desideratum which thus 

 exists in analysis, viz. a neat, expeditious, and accurate method 

 for the determination of bismuth, I began a series of experi- 

 ments, and in the present communication I have to describe a 

 method which I find to yield satisfactory results. It is based 

 upon the fact that chromic acid, when in liquid contact with 

 bismuth, combines in constant proportions to form an insoluble 

 compound, definite in composition, which is produced under all 

 circumstances. The value of this reaction as the basis for a 

 volumetric mode of analysis, depends upon the characteristic 

 colour of chromic acid aud its compounds. I shall proceed to 

 describe, in the first place, the results of some experiments on the 

 nature of the reactions upon which the method is based ; secondly, 

 notice the estimation of bismuth by weight ; thirdly, its deter- 

 mination by volume ; and lastly, adduce the combining ratio of 

 chromic acid and oxide of bismuth. The agent I propose to 

 employ, bichromate of potash, has hitherto never been suggested 

 for that purpose. 



Chromate of potash, KO, CrO^, precipitates, on addition to so- 

 lutions of most metals, chromates corresponding to the formula 

 MO, CrO^, Bichromate of potash, KO, 2Cr03, combines by double 

 affinity with metaUic oxides, as in the case of simple chromate of 

 potash ; the former giving rise to bichromate compounds of the 

 formula M0,2Cr03, which are, without exception, soluble in 

 water. 



A peculiar combination of bichromate of potash takes place on 

 its addition to salts of bismuth, viz. the formation of a simple 

 chromate of bismuth, BiO^ CrO'*, in which each equivalent of 

 chromic acid is united with one equivalent of oxide of bismuth. I 

 found upon inquiry, that the phsenomena of the two equivalents of 

 chromic acid contained in that of bichromate of potash, combining 

 separately with single equivalents of other bodies, took place 

 among the metals with lead and bismuth, and among the alka- 

 line earths with baryta only. I invariably found that acid solu- 

 tions of other bodies remained perfectly clear upon the addition 

 of bichromate of potash. By means of this agent, therefore, 

 bismuth, lead, and baryta may be separated singly, or together, 

 from all other bodies when in solution. I also Ibund that while 

 chromate of baryta is soluble in dilute nitric acid, the chromates 

 of lead and bismuth are comparatively insoluble. The solubility 

 of chromate of bismuth in water, acetic acid, nitric acid, and 

 caustic potash, I determined quantitatively. I immersed a quau- 



