1815.] On Tungsten. 201 
ammonia, and that by the action of that alkali it undergoes a partial 
deoxidizement. I resolved, therefore, to make experiments on the 
solubility of our oxide in carbonate of ammonia. 
Exper. 7.—100 gr. of the oxide rendered yellow in experiment 
Ath were heated with a mixture of half an ounce of subcarbonate of 
ammonia and 2 oz. distilled water, and the mixture was frequently 
agitated. A few air bubbles made their escape. The whole being 
kept almost boiling hot for two hours, the undissolved powder in 
this case also became grey. 
The clear solution deposited on evaporation 66 gr. of tungstate 
of ammonia, having a white colour, a sharp and bitter taste, and 
not effervescing when dropped into muriatie acid; showing that it 
contained no carbonic acid. ‘The dried residue weighed 48 gr. 
Exper. 8.—The 48 gr. of residue in the preceding experiment 
were kept in a red heat for an hour in contact with the atmosphere. 
By this treatment it again assumed a light lemon-yellow colour. 
35 gr. of it were mixed with half an ounce of subcarbonate of 
ammonia and 2 oz. of water, and the mixture was agitated for some 
hours, being kept warm all the time. A lively effervescence took 
place at first. The whole was then gently boiled for one hour, and 
the liquid portion separated from the grey oxide by the filter. By 
evaporating the liquid, 20 gr. of a light reddish-grey powder were 
obtained, which had a sharp bitter taste. The undissolved grey 
oxide weighed 18 gr. 
From these experiments with subcarbonate of ammonia, we see 
that there exists the same difficulty of solution, and the same de-+ 
oxidizement, when tungstic oxide is treated with carbonate of am- , 
monia, But as these experiments, as well as the preceding, with 
caustic ammonia, contradict those of other chemists, as Scheele, 
Bergman, Klaproth, Richter, &c. respecting the solubility of tung+ 
stic oxide in ammonia, | conceived that further experiments were 
necessary in order to clear up this discordance. 
Exper.9.—A small portion, therefore, of tungstate of ammonia 
was converted into yellow oxide of tungsten by digestion in concen 
trated muriatic acid, washing it in a sufficient quantity of water, 
and drying it strongly, but without exposing it to a red heat. 10 gr. 
of this oxide were mixed with two drams of the solution of caustic 
ammonia. ‘The whole was dissolved immediately without the assist- 
ance of heat. ‘The old observations of preceding chemists were 
confirmed by this experiment. 
Exper. \0.—In order to obtain a larger quantity of tungstic oxide 
not dried in a red heat, and therefore soluble in ammonia, 3 oz. of 
Scheele’s tungstic acid were kept boiling for an hour in 6 oz. of the 
same nitric acid which 1 employed in the preceding experiments in 
a porcelain dish upon a sand-bath, and during the whole time the 
mixture was constantly stirred with a porcelain pestle. The whole 
was then evaporated to dryness in a moderate heat. The oxide 
obtained by this process was of a full lemon-yellow colour. A por- 
tion of this being washed with water, and gently dried, dissolved 
