Royal Irish Academy. 103 



but differs from it in being anhydrous, in containing cyanogen, and 

 in yielding hydrocyanate of thylene when decomposed by heat. Its 

 analysis agrees with the formula 6 SOgjSKO, MO,MCy 



If 3 equivalents of ferrocyanide of potassium be supposed to act 

 on 3 of sulphomethylate of potash there is the following equation : 

 3 equiv. Ferrocyanide 3 equiv. Sulphomethylate 



6KCy,3FeCy + 6SO,3KO,3MO = 



1 equiv. G 1 equiv. H 



=4KCy,3FeC2/,MC^ + 6 S 0^,3 KO, M O, M Cy 

 + 2 K O. i. e. 2 equiv. potash. In conformity with this explanation, 

 the liquid in which G crystallizes is alkaline. 



If this explanation be admitted, it will of course apply, mutatis mu- 

 tandis, to the salts A B, C D, E F. The author, however, is not yet 

 satisfied that the salts which he analysed may not have been mixtures, 

 perhaps in definite proportions. No doubt can be entertained that 

 new salts have been formed, but the close resemblance between their 

 properties and those of the salts which yield them, renders the task 

 of purifying and analysing them one of great difficulty. 



April 10. — A paper was read '* On a new variety of Alumn," by 

 James Apjohn, M.D., M.R.I.A., Professor of Chemistry in the Royal 

 College of Surgeons, Ireland. 



This paper commenced with a brief description of the physical cha- 

 racters and chemical properties of the mineral in question, which was 

 found about GOO miles to the north of the Cape of Good Hope, near 

 Algoa Bay, where it occurs in strata whose aggregate thickness is 

 about twenty feet. The specimen described is composed of transpa- 

 rent threads or fibres, exhibiting a beautiful silky lustre, and in ap- 

 pearance closely resembling satin-spar or the finer forms of amianthus. 

 In taste, solubility in water, and other properties, it corresponded 

 with ordinary alumn. It was also easily shown to contain sulphuric 

 acid and alumina, but in addition it contained a base which, though 

 precipitated like alumina by potash, was notredissolved by an excess 

 of the alkali. This, upon examination, turned out to be protoxide 

 of manganese. There was no alkali, but about one per cent, of sul- 

 phate of magnesia. 



In the first attempt at effecting the analysis of the mineral it was 

 foimd that alumina and protoxide of manganese could not be sepa- 

 rated perfectly by potash, as some of the oxide was taken up by the 

 alkali, while a considerable quantity of alumina was left behind with 

 the oxide. The author explained a method of overcoming this diffi- 

 culty, the particulars of which are given in detail in the paper. Tiie 

 following are the results — the numbers in column (2) being the 

 quotients got by dividing those incolumn(l) by the respective atomic 



weights : 



(1) (2) (3) 



Sulphuric Acid, 3279 '8 i 7 4-000 



Alumina, 10-65 -414 2026 



Oxide of Manganese, 7*33 '205 1*003 



Sulphate of Magnesia, 1-08 



Water of Crystallization, .... 48-15 5-350 26-315 



100 



