244 Examination of Brochantite by the Blowpipe. [Oct 



quickly disappeared, and the globule became red from reduced 

 copper. 



With salt of phosphorus, the same as with borax, except that 

 the green colour was not so intense. 



The quantity being so minute, I could not expect to detect 

 the presence of arsenic by its odour. I, therefore, sought for 

 arsenic acid by treating a few minute fragments of the crystals 

 on a slip of glass, with potash and nitric acid, &c. but no indica- 

 tion of its presence was afforded by nitrate of silver. With 

 nitrate of lead, the solution gave a considerable precipitate, inso- 

 luble, when largely diluted, in excess of nitric acid. 



The crystals dissolved completely in muriatic acid without the 

 slightest effervescence, and the solution, diluted with a large 

 quantity of water, gave a white precipitate with muriate of 

 barytes, apparently perfectly insoluble in excess of acid. To 

 ascertain, however, if phosphoric acid be present, I digested the 

 precipitate by muriate of barytes in diluted muriatic acid with 

 heat, decanted the clear fluid, and added ammonia, but not the 

 least cloudiness, indicative of a phosphate, ensued. To be still 

 more certain, I tried the converse of Dr. Wollaston's beautiful 

 and delicate process for detecting the minutest portion of mag- 

 nesia ; that is, I dissolved a portion of the crystals in nitric acid, 

 and to the clear solution added a solution of nitrate of magnesia, 

 and to the mixture an excess of bicarbonate of ammonia. 

 Letters were then described with a glass rod in the solution on 

 ihe slip of glass, and the mixture slightly warmed over the lamp, 

 tut no traces whatever were discernible on the glass. A com- 

 parative experiment made with a similar particle of phosphate of 

 copper gave distinct and strong lines on the first impression of 

 the heat. 



As from the experiment with muriate of barytes, a sulphate 

 appears to be present, a portion of the crystals was heated in 

 pure water, and the liquid tested with muriate of barytes, but 

 no precipitate ensued ; the water did not appear to have 

 dissolved any thing; the appearance of the crystals was wholly 

 unaltered, i could not detect any trace of lime, magnesia, 

 manganese, or iron, in the crystals, nor any decisive indications 

 of alumina or silica; in short, nothing but copper and sulphuric 

 acid ; and yet they appear to be wholly insoluble in water. A 

 particle of a crystal laid in a drop of water on a clean polished 

 bar of iron, and the water evaporated to dryness left no trace of 

 copper, nor any more mark than another drop of the same water 

 evaporated to dryness beside it. 



Prussiate of potash indicated nothing in the solutions but 

 copper. 



From the insolubility of the crystals in pure water, and their 

 fine green colour, it can hardly be doubted that they must con- 

 tain something else besides sulphuric acid and oxide of copper; 



