Intelligence and Miscellaneous Articles. 333 



■a 



To ascertain the influence of this gas on plants previously deve- 

 loped, a sponge with plants of cress completely formed were placed 

 in a bottle filled with it. In two days the plants suffered no change ; 

 but on the third day they became of a yellow colour, and in a week 

 they drooped : when removed to the atmosphere, they recovered their 

 colour and ceased to droop. 



It is to be observed, that the experiments described were made, 

 not only with'seeds, but also with plants, in nitrous oxide exposed 

 to the direct rays of the sun and in the shade, and that in both cases 

 no decomposition of the gas occurred. 



It results from the experiments described, — 



1. That nitrous oxide is not favourable either to the germination 

 of seed, or the vegetation of plants previously formed. 



2. That this gas is not decomposed by the chlorophylle of plant.*,, 

 even when the apparatus is exposed to the direct rays of the sun. 



3. That seeds which have remained for some time in this gas, do 

 not thereby lose the power of germinating in the air. — Journ. de 

 Pharm. et de Ch., Aout 1846. 



METHOD OF DETERMINING THE QUANTITY OF TUNGSTIC ACID. 



M. Marguerite remarks that the usual process for ascertaining the 

 quantity of tungstic acid has been admitted to be inaccurate by all 

 chemists ; and in analysing the supersalts of this acid, the limit of 

 error which may be committed in employing it, may occasion such a 

 difference in their centesimal composition as may make the formula 

 vary one equivalent of acid, or at any rate leave it undecided : in 

 fact, a difference of 1 or 2 per cent, constitutes a tungstate with four 

 or five equivalents of acid. 



M. Berzelius, in his Annuaire for 1841, gives a precise method for 

 estimating tungstic acid in neutral tungstates, by means of nitrate 

 of mercury. M. Marguerite was however apprehensive, that by pre- 

 cipitating the acid tungstates in this manner, the nitric acid set free 

 might act upon the precipitated tungstate of mercury, and render the 

 process inexact. 



The following process M. Marguerite found to be rigorously exact 

 and extremely simple. Put the salt to be analysed in a small platina 

 capsule, and add to it several times its weight of pure concentrated 

 sulphuric acid ; subject the mixture at first to a gentle, and subse- 

 quently to a red heat. 



After the calcination, the residue consists of an acidulous sulphate 

 and free tungstic acid. It is to be mixed and washed on a filter, 

 with water containing hydrochlorate of ammonia, which possesses 

 the property of preventing the tungstic acid from becoming a hy- 

 drate, and passing through the filter, — an effect which is sometimes 

 produced, even after it has been calcined. 



When the last washings cease to precipitate chloride of barium, 

 the residue is to be calcined to expel the hydrochlorate of ammonia, 

 and a few drops of nitric acid are to be added to oxidize any small 

 particles of reduced tungsten which may have appeared, and to dis- 



