Chemistry and Physics. 409 
SCIBN TIFIC:INTSE LLIGENCE. 
I. CHEMISTRY AND PHYSICS. " 
1. On the determination of Gas-densities. Ee gets and 
Victor Meyer, having occasion to make a series of determinations 
of the density of cyanogen n gas at various cesibie ratures, contrived 
for this purpose a simple method. The gas vessel is filled first 
with pure dry air at the temperature at which the determination 
is to be made. Then this air is displaced by a current of hydro- 
gen chloride gas, collected over water and measured. Next the 
hydrogen chloride is displaced by air, After this the gas to oy 
examined is passed through until all the air is replaced b 
gas is again displa hydrogen or air and collected in a 
potash bulb fil ith a liquid which absorbs it completely. The 
merease of the weight of the bulb gives the weight of the gas. 
— “apa - 3 the vessel full “of air and of gas being now known 
r the given temperature the density is easily obtained. The 
aratus consists of a cylinder of glass 200" high, 30" diame- 
ter, with ary tubes attached to the ends, rising considerably 
re 
at t bottom, 40 400" high and about twice the diameter of the inner 
tube, containing the liquid whose boiling point is the tem- 
perature of measurement. Water, aniline, amyl benzoate and 
diphenylamine are used in the glass outer vessel ; but at tempera- 
tures of boiling —— or phosphoric sulphide, the inner vessel is 
spherical and the outer one of iron. Carbon dioxide and hydrogen 
chloride gases gave in this ap aratus densities of 1°53 and 1-26 
respectiv ely. The a pparatus may obviously be used as an air 
thermometer ; - the ee ee the 1, Heb ager : 
sulphur as 426° C.— Ber. Berl. Chem. Ges., xv, 137, 
red 
iat if an iron plate is nae 1 da ey not ‘aly the carbon 
be shown to ake place. even at 250°. a piec ‘e of piano wire, 
imbedded in lampblack, be eo to redness in the reducing 
mg that a diffusion occurs between solids only when they can 
react on one another. Pure silver loses weight when heated in 
ek dry alkali-chloride. But the product darkens on exposure to 
en hence silver chloride must have been formed, free _— 
ng been produced by the oxygen ‘of the air. If a polished 
est ce of artificial iron sulphide be heated on a plate of co oi ina 
current of CO, small quantities of sulphur go from ‘the j iron to the 
