M. Wilkens on Artificial Ultramarine. But 



from that proposed by Breunlin*, wlio considers it to be a com- 

 pound of a mineral of the formula of nepheline with pentasul- 

 phide of sodium. 



But both chemists agree in the fact, that when decomposed 

 by acids, one equivalent of sulphur is liberated as sulphuretted 

 hydrogen, and four equivs. as free sulphur. Wilkens thinks 

 that hyposulphite of soda, with sulphide of sodium, is the colour- 

 ing principle of a silicate of alumina. The sulphur in ultra* 

 marine cannot be replaced by any other body, nor can the sodium. 

 Experiments carefully made with this view, with potash, lime, 

 and magnesia, afforded no ultramarine. Iron exerts no influence 

 in producing the blue colour. 



Green ultramarine, which always precedes the formation of 

 blue, is considered by Wilkens to be a sulphide of sodium com- 

 pound, but he had arrived at no certain results as to its consti- 

 tution, since, from the various methods of its formation, it occurs 

 of very different form and composition. 

 saw ?ddi ill beamUuy) hiofi oniodTR') ^ ''^ Od^'^ bt)i 



- r Dr* ' Grimm t dfescribes -a i^(^ platinum salt;= OH' ' adding 

 caustic ammonia to a hydrochloric acid solution of protochloride 

 of platinum, which had not been neutralized with carbonate 

 of ammonia, a beautiful garnet-red crystalline compound was 

 thrown down. On continuing the addition of ammonia, Mag- 

 nus's salt gradually formed in green flakes ; but the same red 

 crystals were constantly formed, and only disappeared on lon^- 

 continued boiling with excess of ammonia. They were onccs ob- 

 tained in distinct quadratic octahedra of a ruby colour. 'ip^'i 



The salt is difficultly soluble in cold, but more easily in hot 

 water. It is insoluble in alcohol, but completely soluble in am- 

 monia and carbonate of ammonia. 



The analyses lead to the supposition that it is a compound of 

 protochloride of platammohium with chloride of ammonium, 



TT3 l^N, Cl + NH'*Clj but as some of its reactions are not in 



-J ... i +.^u"df='^' 



accordance with this view, the author reserves a dedision on the 



point for further investigation. , = 



'^'^ToitJ investigated and describes several benzoyle compounds, 

 derivatives of benzoic acid. In the preparation of nitrobenzoic 

 acid a slight modification of the usual method was adopted. 

 Melted benzoic acid was added in small portions to a mixture of 

 strong sulphuric and nitric acids and gently warmed for half an 

 hour. By this method no binitrobenzoie acid is formed ; and on 



* Phil. Mag. June, Supplementi>««K p'^tiobfc^s^^o*! ' 

 t Jj\Qh\g'% Annalen, July, p. 95.1 .m'^^^J: IWai'>f 100, 



