A Mixture Which Is Also Known As Brunswick Green Fine Bright Greens

: ON THE SECONDARY, GREEN.

they are suited to the ordinary purposes of mechanic painting, but are

quite unfit for the artist's craft, chrome yellow reacting upon and

ultimately destroying Prussian blue when mixed therewith. For the

latter, cheap cobalts and ultramarines are preferably substituted,

although they do not yield greens of like power and intensity.



Under the names of English Green, Green Cinnabar, &c., 'new' green

pigmen
s have been from time to time introduced, which have turned out

mixtures of Prussian blue and chromate of lead; not made, however, by

compounding the two, but directly by processes similar to the

following:--A mixed solution of the acetates of lead and iron is added

to a mixed solution of the yellow prussiate and chromate of potash, the

necessary acetate of iron being obtained by precipitating a solution of

acetate of lead by sulphate of iron, and filtering the supernatant

liquid. Or; to a solution of Prussian blue in oxalic acid, first

chromate of potash is added, and then acetate of lead.



By the last process, superior and more permanent chrome greens may be

produced, free from lead, by using chloride of barium or nitrate of

bismuth in place of the acetate of lead. Chromate of baryta, or chromate

of bismuth is then formed, neither of which acts on the Prussian blue.



It should be added that where the latter pigment is present, no green

will serve for painting walls containing lime, as its action alters the

tint of the Prussian blue.



TTITLE HOOKER'S GREEN



is a compound of Prussian blue and gamboge, two pigments possessing a

like degree of stability, and perfectly innocuous to each other. It is a

mixture more durable and more transparent than chrome greens made with

chromate of lead. There are two varieties in common use--No. 1, a light

grass green, in which the yellow predominates; and No. 2, a deeper and

more powerful green, with a larger amount of blue.



TTITLE PRUSSIAN GREEN,



like the preceding, is composed of Prussian blue and gamboge; but

contains a very great excess of the former, and is therefore a

bluish-green of the utmost depth and transparency, verging on black in

its deep washes. Yellow ochre may be employed instead of gamboge, but is

not so eligible.



A true Prussian green, which has been recommended as a pigment, can be

produced as a simple original colour, with a base wholly of iron. It is

got by partially decomposing the yellow oxalate of protoxide of iron

with red prussiate of potash. We have made this green and given it a

fair trial, but our verdict is decidedly against it. In colour it is

far from being equal to a good compound of Prussian blue and gamboge,

and it assumes a dirty buff-yellow on exposure to light and air, the

film of blue on the oxalate more or less disappearing.



Another Prussian green, with a base of cobalt, is obtained by

precipitating the nitrate of that metal with yellow prussiate of potash.

According to the mode adopted, and the degree of heat, either a light or

dark green results; but this also is inferior in colour, and presents no

advantage as to permanence.



TTITLE SAP GREEN,



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