$9 Prof. Johnston on the Composition of certain 



This was a task of no slight difficulty, on account of our very 

 limited acquaintance with the nature and properties of the al- 

 buminous combinations found in the different secretions. 

 [To be continued.] 



V. ' On the Composition 'of certain Mifieral Substances of 

 Organic Origin. By James F. W. Johnston, M.A., F.R.SS. 

 L. Sf E.y F.G.S.f Professor of Chemistry and Mineralogy, 

 Durham."^ 



V. Elastic Bitumen of Derbyshire. 



THE elastic bitumens of Derbyshire and Montrelais have 



been analysed by Henry jun. He found them to con- 

 sist of 



From Odin Mine. From Montrelais. 



Carbon 52-250 58*260 



Hydrogen... 7*496 4*890 



Nitrogen ... 0*154 0*104 



Oxygen 40*100 36*746 



100* 100* 



Journal de Chimie Medicale, i. p. 18. 



This analysis is open to two remarks; first, on the excessive, 

 and in the present state of manipulation the almost impossible, 

 refinement of estimating one tenth of a per centage of nitro- 

 gen; and second, on the large amount of oxygen which it 

 indicates. This quantity is so much beyond what we should 

 expect from the appearance of the substance itself, from its 

 chemical relations, and from the circumstances under which 

 it is met with, as at once to awaken doubts of the accuracy 

 of the analysis. 



I have analysed three varieties of the elastic bitumen of 

 Derbyshire, and have obtained a widely different result. 



1 . The first was soft, elastic, adhering to the fingers, yield- 

 ing to slight pressure, of a brown colour and a strong pe- 

 culiar odour. At 212° Fahr. it decreased in weight, giving 

 off" a volatile matter possessing the unpleasant odour of the 

 mass. 



10*052 grs. burned with oxide of copper gave 31*07 grs. 

 of carbonic acid, and 12*01 8 grs. of water. These are equal to 



Carbon 85*474 



Hydrogen 13*283 



98*757 

 Communicated by the Author. 



