Chemical Examination^ Sfc. 279 



6'03, and hardness as 3°, but the difference may in some de- 

 gree be influenced by the greater per-centage of silica con- 

 tained in the specimen. The method of analysis employed 

 was as follows : — 2058 grains weighed into a small glass 

 tube were placed in a flask with 1^ oz. nitroso-nitric acid, 

 closed by a caoutchouc cork, and allowed to stand twelve 

 hours. It was then heated for some time until all sulphur 

 was dissolved, with the exception of a small round globule, 

 which was of a fine yellow colour, and was removed, washed, 

 dried, and weighed. As after ignition it left no residue, it 

 was regarded as pure sulphur. A quantity of white silicious 

 matter, apparently quartz, also remained, and v/as collected 

 on a filter, washed, dried, incinerated, and weighed. 



The solution was now considerably diluted, and precipi- 

 tated, whilst boiling by chloride of barium, and the resulting 

 sulphate of barytes filtered off, washed, dried, and incinerated. 



The excess of barytes in the solution was now removed 

 by sulphuric acid, and removed by filtration. 



The copper was now precipitated by a stream of sulphu- 

 retted hydrogen, the precipitate being washed with water 

 previously boiled and saturated with that gas. The sul- 

 phuret of copper was now dried and ignited for a very long 

 time with excess of air, so as to remove all possible sulphur, 

 and then in the same crucible treated with nitric acid, evapo- 

 rated to dryness, and strongly ignited, so as to decompose 

 any sulphate of copper which perchance had been formed, 

 then cooled over sulphuric acid, and weighed. The fil- 

 trate from which the copper had been separated was now 

 boiled to expel all sulphuretted hydrogen, and oxidized by 

 addition of chlorate of potash ; then precipitated by caustic 

 potash, and the precipitate dissolved off the filter by hydro- 

 chloric acid, neutralized by ammonia, and then precipitated 

 by succinate of ammonia, observing the usual precautions, 

 in order to separate any manganese present. The succi- 

 nate of iron, after being washed on a filter with warm am- 

 monia water to remove the succinic acid, was re-dissolved 

 in hydrochloric acid, precipitated by ammonia, and deter- 

 mined as oxide, using the precaution to moisten the oxide after 



