[ 1« ] 

 XXVI. Intelligence and Miscellaneous Articles. 



ON AN IMPROVED METHOD OF DETECTING ALUMINA. 

 BY MR. J. C. NESBITT. 



THE process depends on the insolubility of the phosphate of alu- 

 mina in acetic acid, and the two following experiments will 

 show the advantages of this test : — 



1st. Two grs. of alum were dissolved in 1000 grs. of water, and 

 a single drop of this solution was mixed with a little solution of 

 phosphate of soda, to which acetate of ammonia and acetic acid had 

 been added ; in a few minutes a precipitate of phosphate of alumina 

 was produced. 



Another drop was mixed with ammonia, and the usual tests were 

 employed to detect alumina, but no precipitate was produced. 



Some ordinary solution of potash was mixed with a strong solu- 

 tion of muriate of ammonia. The mixture showed no change after 

 the lapse of two days. 



Another portion of the same solution of potash was mixed with a 

 solution of muriate of ammonia, containing a few drops of solution 

 of phosphate of soda. A precipitate was produced in the course of 

 twenty minutes or half an hour. 



In order to detect alumina in the ashes of plants, or in substances 

 containing similar ingredients, it is merely necessary to precipitate 

 the oxide of iron (if any be present) and the alumina as phosphates, 

 by the addition, if necessary, of phosphate of soda, acetate of am- 

 monia and acetic acid. This precipitate is to be boiled with a solu- 

 tion of pure caustic potash ; the phosphate of alumina will be dis- 

 solved, and may be again precipitated by muriate or acetate of am- 

 monia and acetic acid. — Proceedings of the Chemical Society, part 



ON A NEW SUBSTANCE FROM COCHINEAL. 



At the Meeting of the Chemical Society for March 16, 1846, 

 Mr. Warren De la Rue described a new body which he had ob- 

 tained from cochineal, a subject he has been for some time past 

 investigating, and which bears a remarkable similarity to a substance 

 which Liebig has lately produced by the action of potassa on caseine, 

 to which he assigns the composition C, fi , N, H 9 , O b , at the same time 

 stating that the formula requires confirmation. Though the analyses 

 of the new substance differ somewhat from this formula (its compo-. 

 sition appearing to be C 18 , N, H u> O e ), yet the agreement of its 

 properties with those assigned by Liebig to the substance described 

 by him, leaves but little doubt as to the identity of the two bodies. 

 A specimen of Liebig' s substance, furnished by Dr. Hofmann, agrees 

 perfectly in its physical characters. 



The new body is obtained from cochineal by the following 

 means: — The colouring principle being first separated from an in- 

 fusion of cochineal, the mother-liquor is to be carefully evaporated 

 in a water-bath to the consistence of a syrup, when there appears 

 floating in it a small quantity of granular chalky-like masses, which 

 being collected on a filter is kept warm, and, when drained, well- 



Phil. Mag. S. 3. Vol. 29. No. 192. August 1846. L 



