828 Intelligence and Miscellaneous Articles. 



were 0-005 metre to 0*012 metre in length. There was a slight green 

 tint on the top of one of these plants ; the other was quite white. 

 The grains sown on the 27th and 28th of July had not sprouted 

 on the 31st of July at 2 o'clock; the plants sown on the 24th and 

 26th of July were 0*010 metre to 0*060 metre in length; they were 

 all very green, and strongly turned towards the light. The grain 

 sown on the 27th of July had sprouted ; the plants were 0*020 metre 

 to 0*030 metre high, and there was a little green on the top of one 

 of them. 



At 1 o'clock on the 1st of August the plants continued to grow 

 just as in the light. The rye sown on the 28th of July had sprouted, 

 but showed no green. 



On the 2nd of August, at 2 o'clock, all the plants continued to 

 grow ; the rye which had sprouted on the night before was deci- 

 dedly green. 



The seeds kept in the dark for the sake of comparison, gave plants 

 which were completely yellow. — Comptes Rendvs, Aug. 5, 1861. 



NATURE OP THE DEPOSIT WHICH PORMS UPON THE COPPER 

 EMPLOYED IN REINSCIl's TEST POR ARSENIC. 



Lippert has made a careful examination of the crust which forms 

 upon bright metallic copper when this is placed in a solution of 

 arsenic acidified with chlorhydric acid. This coating had been 

 pretty generally mistaken for metallic arsenic until Fresenius (in his 

 Anleitung zur qualitative)! Analyse, lOte Aufl., Braunschweig, 1860, 

 p. 141) called attention to the fact that it contained a large quan- 

 tity of copper. From the experiments of Lippert, it now appears 

 that the crust in question contains only 32 per cent, of arsenic, 68 

 per cent, of its weight being copper. This composition having been 

 nearly constant in several specimens which he analysed, Lippert 

 maintains that the compound is a definite alloy, As Cu 5 . When 

 ignited, at the temperature of a combustion furnace, in a current of 

 hydrogen, the compound lost only 7 per cent, of its weight, an alloy 

 of the composition As Cu G (same as that of the miueral Domeykite 

 of F. Field) being formed. 



The delicacy of Reinsch's test is evidently directly referable to the 

 large amount of copper which the characteristic coating contains ; 

 for a proportionally small quantity of arsenic is thus obtained in an 

 enlarged and, as it were, more tangible form. But, on the other 

 hand, it is not easy to prove in a simple manner the presence of 

 arsenic in this crust ; for only a small portion of the arsenic can be 

 volatilized in a current of hydrogen, and even if the alloy be first 

 oxidized in a current of air and then reduecd in a current of hy- 

 drogen, the per-centage of arsenic only falls from 32 to 20. By far 

 the largest portion of the arsenic is therefore kept out of sight. 



For the details of this interesting research, and the author's dis- 

 cussion of the proposition of Reinsch and v. Kobell to estimate 

 arsenic quantitatively by determining the amount of copper which 

 dissolves while the arsenic is being precipitated, we must refer to 

 the original article. — Journ./iir Prakt, Chemie, vol. lxxxi. p. 168. 



