CHROMATE OF POTASSA: 



A RE-AGENT FOR DISTINGUISHING BETWEEN THE SALTS 

 OF BARYTA AND STRONTIA. 



Having had occasion some months since to examine a 

 specimen of fibrous celestine from Niagara, I was led to 

 suspect from its specific gravity that baryta was present. 



With this supposition I examined for baryta, in the usual 

 way, with fluo-silicic acid; in fact, the only certain method 

 that I was aware of. The indication that this test gave of its 

 presence was so unsatisfactory that it led me at once to search 

 for a more decisive and more delicate distinguishing test, and 

 the following was the result of my labor. 



It will be needless to detail the various re-agents that I had 

 recourse to in my experiments, but suffice it to say chromate 

 of potassa satisfied my most sanguine wishes, for no re-agent 

 with which I am acquainted acts so promptly upon any body 

 as does this upon the salts of baryta; and moreover, so delicate 

 is this test that in one of my experiments, in which a grain 

 of chloride of barium was dissolved in one gallon of water, it 

 gave immediate indication of the presence of baryta, although 

 sulphuric acid failed to do so ; in fact, it will affect perceptibly 

 a solution that contains less 'than one hundred-thousandth part 

 of baryta. 



When a strong solution of chromate of potassa is poured upon 

 a strong solution of a salt of strontia a precipitate (similar to 

 that which is produced when a salt of baryta is used) will take 

 place. Solutions of these two salts of ordinary strength will 

 not affect each other. 



Lest this fact should, under any circumstance, cause erro- 

 neous conclusions, I sought for some acid which would dissolve 

 the one precipitate and not the other. Acetic acid is the only 

 acid among the many that I have tried which answered this 

 end. If a small quantity of dilute acetic acid (common acetic 



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