410 Dr. Thomson's Analijsis of Needlestone. [Dec 



which deliquesced in the air, except 0*4 gr. of sulphate of 

 lime. 



The liquid being diluted with water was mixed with oxalate of 

 ammonia. A precipitate fell, which was washed, dried, and 

 heated to whiteness . There remained a white powder weighing 

 0*58 gr. and possessing the properties of lime. 



The residual hquid had a shghtly yellow colour. It, therefore, 

 contained iron. It was mixed with a hquid of the same natm-e 

 derived from the white powder, which still remains to be exa- 

 mined. It appears from the preceding statement that a little 

 muriate of lime and muriate of iron were held in solution by the 

 excess of carbonate of ammonia contained in the liquid. The 

 chief object of the preceding experiments was to see whether 

 the needlestone contained soda ; but I could discover no traces 

 of any such alkali. 



The precipitate thrown down from the acid solution by means 

 of carbonate of ammonia was digested for 24 hours in a mode- 

 rately strong ley of caustic soda. The greatest part of it was 

 dissolved, but not the whole. The clear soda ley was drawn off 

 by a syphon, and the undissolved portion was repeatedly edul- 

 corated by distilled water. All these liquids were mixed toge- 

 ther, and a solution of sal ammoniac poured into them as long as 

 any precipitate continued to appear. The precipitate thus 

 obtained was alumina. It weighed, when dried at a tempera- 

 ture not exceeding 212°, 26-8 grs.; but this weight, on exposure 

 to a red heat, was reduced to 14-56, which was alumina. 



The portion which had resisted the action of the soda ley was 

 digested in muriatic acid. It dissolved completely, except 

 0-9 gr. which was a grey powder, readily fusing into a glass with 

 potash. It was, therefore, sihca slightly tinged by iron. 



The muriatic acid solution was evaporated to dryness, and 

 redissolved in water, in order to get rid of the excess of acid. 

 It was then mixed with oxalate of ammonia ; a white precipi- 

 tate fell ; it was washed, dried, and exposed to a white heat. 

 It now weiglied seven grains, and possessed the characters of 

 pure lime. 



Into the liquid thus freed from lime a solution of sal ammoniac 

 was poured, a quantity of alumina precipitated, which, after being 

 washed, dried, and heated to redness, weighed 1-08 gr. It 

 seems to have been protected by the hme from the action of the 

 soda ley. 



Ammonia being dropped into the residual hquid, a shght pre- 

 cipitate in flocks appeared. At first it was whitish, but it 

 became yellow when collected at the bottom of the vessel ; and 

 when edulcorated and dried, it was of a dark red. It possessed 

 the properties of peroxide of iron, though probably, from the 

 mode of obtainino; it, some masinesia was mixed with it. The 

 weight was 0'3 gr. 



Phosphoric acid was now dropped into the liquid, a very 



