262 Professor Johnston on Middletonite, 



of 400° Fahr. Thrown on a red cinder it burns like resin 

 with much smoke, cakes, and leaves a bulky charcoal, which 

 afterwards disappears without residue. 



Alcohol, aether, and oil of turpentine boiled on the mineral 

 in the state of powder, acquire a yellow tint, but on distillation 

 the coloured solutions leave a mere trace of a dark-coloured 

 friable resinous matter. 



Heated in a close tube over the flame of a lamp it melts, 

 blackens, and gives empyreumatic products. The residual 

 charcoal burns away in the air with extreme slowness, leaving 

 an almost inappreciable quantity of a white ash; 3'02 grs. 

 left 0-005. 



In boiling nitric acid it softens, melts, causes an emission of 

 red fumes, and slowly disappears, giving a brown solution. 

 From this solution on cooling a brown flocky matter falls, 

 which is more fully precipitated by the addition of water. 

 The yellow supernatant acid liquid gives no precipitate with 

 acetate of lead or nitrate of mercury. 



Concentrated sulphuric acid dissolves it in the cold, giving 

 a dark-brown solution and evolving sulphurous acid. 



Burned with oxide of copper, 



4j'35 grs. gave 13*6 grs. of carbonic acid, and 3*135 of water, 

 4*56 grs. gave 14*09 grs. of carbonic acid, and 3*295 of water. 

 5*18 grs. gave 16*265 grs. ofcarbonic acid, and 3*755 of water. 



These results give the following for the constitution of the 

 mineral: — 



1. 2. 3. 



Carbon... = 86*437 85*440 86*738 



Hydrogen = 8*007 8*029 8*046 



Oxygen... = 5*563 6*531 5*215 



100*007 100- 10 

 This agrees with 



20 Carbon = 15*2875 86*506 



11 Hydrogen = 1*3727 7*780 



1 Oxygen = 1*0000 5*714 



17*6602 100* 



and it may be represented by the rational formula 



This formula is analogous to that of Dumas and Peligot, 

 Cjo Hg + S HO, for the supposed hydrate of oil of turpentine.* 

 "Whether the rational formula above given, however, be the true 



♦ See Lond. and Edinb. Phil. Mag. vol. vii. p. 537.— Edit. 



