162 Miscellaneous Intelligence. 



acted on a portion of the acid, taking its oxygen and leaving it's ni- 

 trogen in the state in which it might combine with the carbon and 

 produce the cyanogen. 



4. Crystallized Carbon — Artificial Plumbago. — At page 15£), of our 

 last volume, is an account of artificial plumbago formed in gas retorts, 

 from a paper by the Rev. J. J. Conybeare, in the Annals of Philosophy . 

 Mr. Herapath, in a late paper in the Philosophical Mag. lxi. 423, 

 has shewn that this substance is not what it was at first supposed to be, 

 inasmuch as it is pure carbon. Mr. Conybeare had operated on a 

 portion taken from near the side of the retort, and hence the iron he 

 found in it. As observed by Mr. Herapath, at the Bristol gas works, it 

 is hard and very solid with a mammellated surface, from which scales 

 may sometimes be detached. Its specific gravity is 1.865. When bro- 

 ken its crystalline form is very visible, and may be compared to 

 starch. Mr. Herapath thinks its primitive form is the tetrahedron. 

 In fine powder it loses its grey lustre and becomes a deep black. 



When burnt with peroxide of copper, it requires so much heat that 

 the black glass tubes generally give way. Even with chlorate of po- 

 tassa it is necessary to repeat the process several times, but little being 

 consumed each time. Nitre has still less effect on it. It is a good 

 conductor of electricity. 



Mr. Herapath remarks, that as it is found in thin layers, it is evi- 

 dent that its source is the gas, and its deposition on the hottest part of 

 the retort, shews that coal gas should not be exposed to a greater heat 

 than that at which it is produced. It is observed, too, that if this sub- 

 stance should turn out to be of the same composition as the diamond, 

 and the only difference be that the diamond has twice the number of 

 atoms in the same space, which is probable, from its specific gravity 

 being 3.5, it might throw some light upon the cause of opacity and 

 transparency. 



[We would just remark here, that the necessary presence of iron in 

 plumbago is a point not conceded by all chemists. — Ed.] 



5. Action of Steam on Solutions of Silver and Gold. — The following 

 observations on the action of steam on solutions of silver and gold, 

 were made by Professor Pfaff, whilst investigating the volatility of mu- 

 riates contained in boiling water. When the vapour of pure distilled 

 •water is made to pass through a solution of nitrate of silver, the solu- 

 tion assumes all the shades between yellow and dark brown, accord- 

 ing to its concentration, and the time the steam has passed through it. 

 When the solution has acquired 212° the colour increases rapidly. 

 If several glasses are connected, and successively raised to the boil- 

 ing point, by the steam passing through them, all become coloured. 

 Nitric acid destroys the colour of this solution of nitrate of silver, and 

 whilst the steam is acting oxygen is disengaged. When steam is 

 passed through a solution of gold, a blue liquid is produced, like that 



