272 Chronicles of Science. [April, 



Cliahjpiie, recognizable by tlie carboniferous deposit which they 

 give under the action of acids. 



3, The sulphuretted ii'on, or Troilite, which appears in nodules 

 and in veins. 



4. The phosphide of iron and nickel or ScJireihersite. 5. Gra- 

 lihite. 6. The external crust. 7. The stony particles or crystals. 

 8. The gases retained by occlusion. 9. Several compounds which 

 are only met with exceptionally, as Chromite, (fee. Space will not 

 allow us to give in detail the very ingenious methods adopted by 

 the author for separating these ditierent substances. It must be 

 sufficient to say that he has succeeded in isolating each of these 

 components in a state of purity and ascertaining their composition, 

 with the exception of the gases, owing to his ha^dng employed for 

 their separation a method which Professor Graham has since shown 

 to be inapplicable. 



Professor Stas, to whose researches chemists are so much in- 

 debted, has published a modification of Gay Lussac's method of 

 estimating silver in the wet way. In the ordinary process a 

 standard solution of salt is employed, but, as the precipitated 

 chloride of silver is soluble in a solution of salt, it is impossible to 

 carry out this principle to the minute accm-acy W'hich is sometimes 

 recpired. M. Stas has now discovered that by substituting a 

 bromide for a chloride in precipitating silver, this error may bo 

 absolutely removed. 



An Italian chemist, Massino Levy, has devised a method of pre- 

 paring nitrogen gas, w^hich may be useful in some cases. It consists 

 in heating bichromate of ammonia in a retort; the salt is trans- 

 formed into green sesquioxide of chromium, and disengages vapom* 

 of water and nitrogen gas. In the ordinary process of bleaching 

 wood-pulp it is very difficult to avoid a yellow or reddish tint, and if 

 ii'on is present the paste generally blackens in a very short time. 



M. Orioli has discovered a process of bleaching in which these 

 objectionable results are obviated. To 100 kilogrammes of wood- 

 piilp, 800 grammes of oxalic acid are added ; this serves the double 

 purpose of bleaching the colouring matter already oxidized, and of 

 neutrahzhig alkahue principles. Two kilogrammes of sulphate 

 of alumina, free from iron, are now added. This does not bleach of 

 itself, but it forms with the colouring matter of the wood a nearly 

 colourless lake, which enables the brilliancy of the product to bo 

 heightened. 



At one of the recent meetings of the Manchester Literary and 

 Philosophical Society, ]\Ir. Sidebotham drew attention to the large 

 number of galls, wliich appeared to be much commoner now than 

 they were a few years ago. They were produced by the gall fly, 

 Sijnijps Lignicola ; and, from experiments which he had tried, it 



