90 An Account of, and 
This has not yet been tried as a water colour, ‘nor 
have I received any account of their being ufeful 
oil-colours, although .I have given fome of each of 
them to different Painters, as alfo a portion of fome 
_ of the next preparation. 
Thinking that the Aluminous Earth was the reafon 
of the fponginefs of the colours, when ufed as water 
colours, I thought, by precipitating the Mother-water 
of Soda, Phofphorata with a martial folution alone, 
it might produce a colour free fram that fponginefs 
complained of; therefore I added to the Mother- 
water above-mentioned, a faturated folution of 
Martial Vitriol, and a very copious precipitate was 
formed, but of a lefs beautiful colour than either the 
firft or third. The precipitate was very light, and 
required fome length of time to fettle: it was 
wafhed till perfectly taftelefs, and although it 
occupied much fpace, being fo very expanfive, it 
yielded a lefs proportion of dry colour than either of 
the former proceffes, and was not fo deep a blue as 
To. 1, 
As this laft colour, when dried, had a little brown- 
if tinge on its furface, I concluded it proceeded 
from its having fome ochry matter mixed with it; 
to free it from which, I added a little Oil of Vitriol 
to a fmall portion of it, and the whole became of 
a dirty green, which, on being poured into water, 
turned of a deep blue. This was well wafhed to free 
it from all acidity ; but Pr colour did not appear to 
be improved. 
In 
