n 
Copper, 
The experiments made by Mr. Brown with the prussic 
lixivium on various metallic solutions do not merit parti- 
cular attention, as the results evidently show that a very 
large proportion of the alkali remained unsaturated with 
prussic acid, and thus the effects appeared different when 
the lixivium was prepared with blood or with muscle. 
Bergman has, however, more accurately observed the 
properties of metallic precipitates , (Opuscula, tom. ii. p. 
385), and especially notices the various colours of the 
prussiates ; but neither he nor any other chemist, as far 
as I am acquainted, has pointed out to artists the utility 
of prussiat of copper as a pigment. During some late ex- 
periments, I was much struck with the beauty of this 
precipitate, and was therefore induced to make several 
trials of it as a paint : the results exceeded my most san- 
guine expectations. I afterwards prepared a large quan- 
tity, which at my request several gentlemen (particularly 
B. West, Esq. P. R* A., John Trumbull, Esq., and Sir 
H. C. Englefield,) were so obliging as to try in oil, and in 
water ; and I have had the satisfaction to learn, that in 
beauty and intensity it surpasses every brown paint now 
in use, with the additional advantage, that, by reason of 
its purple tint, it forms with white various shades of bloom 
or lilac colour, which do not appear liable to fade like 
those which are formed by means of lake. 
The prussiates obtained from acetite, sulphate, nitrate, 
and muriate of copper, are all very beautiful ; but the 
finest and deepest colour is afforded by the muriate. I 
have found also that prussiate of lime call be better de- 
pended upon for this purpose than prussiate of potash. 
The best mode, therefore, of forming this pigment, is to 
take green muriate of copper, diluted with about ten parts 
of distilled or rain water, and to pour in prussiate of lime 
until the whole is precipitated : the prussiate of copper is 
then to be well washed with cold water on the filter, and 
to be dried without heat.™ 14 Phil* Mag . 359, 
