93 
1-114, and containing 11-283 per cent of the anhydrous 
salt. The solution of tungstate of sodium was saturated 
(at common temperature), and contained about one-third 
its weight of dry salt. A mixture of equal parts of these 
solutions gave no precipitate in the cold, but quickly crystal- 
lized when warmed, the crystals being difficultly soluble, and 
leaving a very slight residue of an insoluble variety of tungstic 
acid, or of some compound of that acid. But when the 
mixed solutions above described were very little diluted, the 
solution remained perfectly clear at any temperature, until 
the fluid was concentrated by evaporation, when no precipi- 
tate, but clear crystals appeared. It is only, therefore, in 
very concentrated solutions that tungstate of sodium gives — 
not then a precipitate — but crystals, with sulphate of 
magnesium. The chloride of magnesium solution behaves 
similarly, though it was not so closely examined. 
(2.) The behaviour of tungstate of sodium with solutions 
containing calcium and magnesium. The earlier experiments 
seemed to indicate that the presence of magnesium did not 
at all interfere with the precipitation of the calcium. But on 
continually diminishing the quantity of the calcium salt 
while that of the magnesium salt was kept constant, it was 
found that the latter exercised a very appreciable solvent 
power. The limiting experiment was as follows : — To 5 cc. of 
a solution containing 7 parts in 100,000 of sulphate of calcium, 
were added 3 cc. solution of sulphate of magnesium, contain- 
ing 1T283 per cent anhydrous salt, 12 cc. water, and a few 
drops of tungstate of sodium. There were thus, in 2,000,000 
parts of fluid, 35 parts sulphate of calcium, and 33,849 parts 
sulphate of magnesium — the remainder being water, except the 
small quantity of tungstate of sodium. The reaction was not 
visible till the fluid reached the temperature of 70° C, when 
it became apparent, and, on putting it aside to cool, a per- 
fectly distinct film formed on the glass. A similarly attenu- 
ated solution of the lime salt, but containing no magnesium, 
