270 Scientific Intelligence. 



thin glass tube, it may be boiled for hours without decomposition. 

 Acids produce the contrary effect, causing the immediate destruction 



of the nitrite. 



_■ The author proposes the following easy process for nitrate of ammo- 

 nia. An excess of caustic ammonia in a platinum crucible is placed in 

 a cooling mixture. Into this is to be passed very gradually the nitrous 

 vapor, from the dry distillation of nitrate of lead. The solution must 

 be evaporated in an atmosphere of ammoniacal gas, over lime. 



The decomposition by sulphur, has been previously noticed by 



Pelouze. 



rf estimating the Nitrates 



G. C. S. 



by J. Pelouze, (Comptes Rendus, Feb., 1847.)— The solubility of all 

 the nitrates preventing any application of the usual methods, and yet 

 the large quantity of nitre consumed annually in the manufacture of 

 gunpowder requiring some mode of determination approaching accu- 

 racy, many ingenious processes have been devised, and of these a very 

 complete history is given in the first part of the paper. 



A method has been recently proposed by M. Gossart, which consists 

 in mixing the salt with sulphuric acid and decomposing it by a normal 

 solution of protosulphate of iron— the completion of this action being 

 determined by ferridcyanid of potassium, for when this indicates the 

 presence of protoxyd of iron, it is known that all the nitre has been 



consumed. The quantity of solution used, gives by a simple calcula- 

 tion thp nimntiwr r*f «;.»;« „ -J ■. ° J r 



tion the quantity of nitric acid or nitre. 



.. ....<= ^ucmiLj, ui uurju acia or nitre. 



M. Pelouze considers the process as original with M. Gossart, and 

 happy in its invention. Certain difficulties however, have led to im- 

 provements by Pelouze, which seem to give the method a high degree 

 of accuracy. He first determined the quantity of pure nitrate of potash 

 requisite to peroxydize a known weight of pure iron, (piano wire being 

 selected as the purest and most convenient.) 2 grms of wire dissolved 

 m an excess of hydrochloric acid, on an average required 1216 grms- 

 of nitrate. This decomposition involves 6 equivs. iron and 1 equiv. 

 nitrate, the acid being decomposed into deutoxyd of nitrogen, which is 



given off, and into oxygen, which produces the perchlorination of the 

 iron. Thus • r 



,-.. 6FeCI :+ N0 5KO-j-4HCI=4HO+KCl+N0 2 +3(FeCl 3 ). . 



(ltns reaction is proposed as an excellent method of preparing the 

 deutoxyd of nitrogen.) As the presence of chlorids and sulphates in the 

 crude nitre does not interfere, it is only necessary to operate upon 

 2 grms. iron and 1-216 of nitre, and by a standard solution of chame- 

 leon mineral (permanganate of potash), ascertain how much iron re- 

 mains to be peroxydized. The method of preparing and using this last 

 solution will be found in this Journal for September, 1846, p. 257. 



In an actual analysis, 2 grms. of wire are placed in a suitable nasK 

 with 80 to 100 grms. strong hydrochloric acid ; the flask is closed by a 

 cork having a fine tube in it. After dissolving the iron with a gentle 

 heat, 1-216 grms. of the nitre to be examined, are added, the fla* 

 closed and the whole boiled. As soon as the gas has escaped, and the 

 brown color disappears, the liquid becomes clear and yellow-atte 

 boiling five or six minutes it is poured into a quart flask, the wash water 

 added and water to fill the vessel. The normal solution of permanga- 

 nate is then applied until after agitation a faint rosey hue remains. 



P 



