His terminology was vague and provoked caustic criticism from Berzelius; he assumed that all molecules contained two atoms, and consequently the atomic weights deduced from vapour density determinations of sulphur, mercury, arsenic, and phosphorus were quite different from those established by gravimetric and other methods.
That orthoboric acid is a tribasic acid is shown by the formation of ethyl orthoborate on esterification, the vapour density of which corresponds to the molecular formula B(0C2H5)3; the molecular formula of the acid must consequently be B(OH) 3 or H 3 B0 3.
For higher temperatures the bulb of the vapour density tube is made of porcelain or platinum, and is heated in a gas furnace.
This fact, coupled with the determination of the vapour density of the gas, establishes the molecular formula CO.
Its vapour density agrees with the molecular formula C302, and this formula is also confirmed by exploding the gas with oxygen and measuring the amount of carbon dioxide produced (see Ketenes).
Biltz (Ber., 1888, 21, p. 2013; 1901, 34, p. 2490) showed that the vapour density decreased with the temperature, and also depended on the pressure.
It melts at below red heat to a brown mass, and its vapour density at both red and white heat corresponds to the formula Cu 2 C1 2.
This subject owes its importance in modern chemistry to the fact that the vapour density, when hydrogen is taken as the standard, gives perfectly definite information as to the molecular condition of the compound, since twice the vapour density equals the molecular weight of the compound.