86 Dr. T. Thomson oti Pyroxylic Spirit and its Compounds. 



studies." These particulars may interest those readers of 

 your Magazine who have ever paid any attention to the hi- 

 story of the ancient geometry. 



XIX. Note of an Analysis of Colophonite. By Mr. T. 



Richardson.* 

 T^HE specimen subjected to analysis appeared remarkably 

 -*■ pure, and was sent from Norway to my friend Mr. Hut- 

 ton. It possessed the following characters : 



It consisted of small round particles which could easily be 

 detached from each other; spec. grav. 3*610; colour yellow, 

 with a shade of brown ; semitransparent ; fracture uneven ; 

 lustre resinous. 



20 grs. of the mineral analysed with every care in the 

 usual way afforded the following result : 



Silica 37*60 containing 19*54; oxygen. 



Alumina 14*40 6*72. 



Perox.ironandj ^3.3^ 4*09}l^*^l 



manganese... j -' 



Magnesia 6'B5 " "- V 10-S4 



Lime 27*80 ..., MUdi 



Water 1*00 



2*53 \ 

 7-81/ 



100*70 

 which evidently corresponds with the formula 



(Ca O Mg 0)3 Si 03 + (Al2 O3 Ye^ O3) Si O3 



and also agrees with Trolle Wachtmeister's fundamental 

 formula for the garnet, viz. 3 Re, Si O3 + Rg O3 Si O3; but 

 differs from his analysis in containing alumina, which has re- 

 placed a certain quantity of peroxide of iron, hereby adding 

 one more to the many already existing proofs of the isomor- 

 phism of these two bodies. 



XX. On Pyroxylic Spirit and its Compounds. By Thomas 

 Thomson, M.D., F.R.S., S^c. and Regius Professor of Che- 

 mistry in the University of Glasgow. 



[Continued from p. 51.] 



^ 1. Sulphate of methylene, 



-ly jO compound made from alcohol corresponding to this is 

 IN known. The simplest method of obtaining it is to distil 

 one part of pyroxylic spirit with eight or ten parts of concen- 



* Communicated by the Author. 



