Dr. J. Stenhouse on Alpha- and Beta-Orcine. 8 



substance and oxide of copper in the tube, and then to dry it 

 with an exhausting syringe, as is usually done. 



It is plain from the result of these analyses, that anhydrous 

 orcine has lost three atoms of water, and that its probable 

 formula is C 21 H 12 6 , that of hyd rated orcine being C 21 H 15 9 . 



I subjoin the results of previous experimenters on anhydrous 

 orcine, with which it will be seen that these analyses agree 

 pretty closely. 



10000 100*00 100-000 



In order to corroborate this determination of the atomic 

 weight of orcine, which, it must be confessed, still remains 

 somewhat doubtful, I made repeated attempts to prepare the 

 lead salt previously described both by Dumas and Schunck, 

 but I am sorry to say with by no means satisfactory results. 

 This perhaps is not to be wondered at, when we consider how 

 easily alterable orcine is. In my first trials, I treated an 

 aqueous solution of orcine with a very slight excess of sub- 

 acetate of lead. The precipitate in the course of a few minutes 

 assumed a deep red colour, and the compound appeared so 

 unstable, that much of the orcine was removed by the wash- 

 water ; so that the more the precipitate was washed, the greater 

 was the amount of oxide of lead it contained. In some sub- 

 sequent trials, when the quantity of subacetate of lead which 

 was added was not sufficient to precipitate the whole of the 

 orcine in the solution, the precipitate, though reddish-coloured, 

 was not nearly so deeply coloured as when a slight excess of 

 base had been employed. The amount of oxide of lead in 

 these precipitates was however greatly diminished ; and though 

 frequently repeated, I never could get the results of the various 

 trials to agree in a satisfactory manner. Mr. Schunck admits 

 that his experiments were somewhat similar. I subjoin the 

 results of a few of my experiments. 



I. Orcine precipitated by a slight excess of subacetate of 

 lead, 1-305 grm. salt gave 0*467 PbO and 0'525 Pb=1081 

 PbO = 82-83 PbO per cent. 



II. Where part of the orcine remained in solution, 0-773 

 salt gave 0-1383 PbO and 0-371 Pb m 0*5379 PbO = 69*58 

 PbO per cent. 



III. Prepared in the same way, but at a different time, 

 0-667 salt gave 0*200 PbO and 0*231 Pb=0*4488 PbO = 67*28 

 per cent. 



B2 



