296 Mr George Fownes on the Existence of 



In the examination of unaltered felspar, I failed, unfortunately, 

 in getting a conclusive result. The mineral, although reduced to 

 very fine powder by trituration in a mortar of Swedish porphyry, 

 was found to be so hard and dense as to resist completely the 

 action of the acid at a boiling temperature. An insignificant quan- 

 tity of oxide of iron was dissolved out, in which no phosphoric acid 

 could be detected. 200 grains of the powdered felspar were then 

 fused with a large excess of carbonate of soda ; the mass was treated 

 with w^ater, filtered, the solution supersaturated with nitric acid, and 

 evaporated to dryness ; water was then poured upon the residue, and 

 the whole placed upon a filter. The solution was then examined, 

 as before, for phosphoric acid, but with an indistinct and doubtful 

 result. Too small a quantity of the felspar had been used, and the 

 mass of nitrate of soda present interfered too seriously with the 

 action of the tests to render their evidence of any value. A far bet- 

 ter mode of investigation would be, to act upon the powdered mineral 

 with hydrofluoric acid, in the manner recommended by some analysts 

 in the examination of natural silicates containing an alkali ; not 

 being, however, in possession of the necessary platinum vessels, I was 

 obliged to abandon the attempt. 



Other substances were then tried with very decisive results. The 

 method of proceeding adopted was very much the same as that already 

 described. The minerals were finely powdered in the porphyry mor- 

 tar, and boiled, as before, with dilute hydrochloric acid. All were 

 much more readily attacked than the porcelain clay, and yielded 

 solutions containing a large quantity of alumina and oxide of iron. 

 The liquid was separated from the insoluble part by decantation, 

 evaporated nearly to dryness, water added, and then an excess of 

 ammonia. The copious bulky precipitates obtained were washed 

 and digested in dilute acetic acid, which has the property of dissolv- 

 ing, with great facility, both oxide of iron and alumina, while it 

 leaves untouched the phosphates of those bases. The undissolved 

 residue was dried, ignited, fused with silica and carbonate of soda, 

 and the product examined in the manner already described. The 

 addition of silica is indispensable to the retention by the whole of 

 the alumina in an insoluble condition. Phosphate of alumina is not 

 decomposed by carbonate of soda by fusion, or only partially, and is, 

 besides, soluble in an aqueous solution of that salt. 



The results of the examination may be thus briefly stated : — 

 Dark grey vesicular lava from the Hhine, used at Cologne as a 

 building stone, being exceedingly stro7ig and durable, — Enough of 

 phosphate of soda was extracted from 1000 grains of this substance 

 to exhibit the yellow phosphate of silver, and the phosphate of mag- 

 nesia and ammonia on a large scale. The phosphoric acid might 

 be said to be very abundant., that is, comparatively speaking. No 

 attempt was, however, made to estimate it quantitatively, as the ope- 

 ration is attended with great difficulty, and the result of doubtful 



