Page 433 - Copper and Bronze in Art: Corrosion, Colorants, Getty Museum Conservation, By David Scott

RECIPE 25 COPPER ORTHOARSENITE
Copper orthoarsenite was made in the laboratory following Gmelin's (i965) recipe as follows:
In a 31 beaker, 56.2 g of CuS0 4 - 5 H 2 0 was dissolved in 375 ml of water and heated to boiling. In
an 800 ml beaker, 13.33 g of A s 2 0 3 and 7.16 g of Na 2 CO s (hydrate) were dissolved in 585 ml of
water. The A s 2 0 3 and Na 2 C0 3 solution was gendy heated to the boiling point until all the A s 2 0 3
had dissolved. The solution was then allowed to cook for 5 minutes to expel all of the free C 0 2 .
A heated solution of copper sulfate was added to the first solution drop by drop until a pre­
cipitate had formed. This fine green powder precipitate was cooked in suspension for another
5 minutes, then cooled, filtered off, and washed well with hot water. Finally, the product was
dried at loo °C.

RECIPE 26 COPPER DIARSENATE I
Copper diarsenate I was made in the laboratory following Gmelin's (i965) recipe, as follows: In
a 3 1 beaker, îoo g of CuS0 4 - 5 H 2 0 was dissolved in 364 ml of cold water (the solution is nearly
saturated). A solution of NaAs0 2 was prepared with 12.73 g of Na 2 C0 3 and 23.75 g of A s 2 0 3 in
312 ml of water, expelling the C 0 2 by gently bringing the solution to a boil and cooking for
5 minutes. The solution was then cooled to room temperature and precipitated at 22-24 °C.
The precipitated product was allowed to stand overnight. Because the suspension is very diffi­
cult to filter, it is easier to make the precipitate into a paste. Water was added to the paste twice,
then decanted. This washing process does not take too long because the product hydrolyzes eas­
ily. The product was dried at 100 °C.

RECIPE 27 EMERALD GREEN, BEARN'S METHOD
Emerald green was made in the laboratory, following Beam's (1923) recipe by dissolving 2.5 g of
sodium carbonate in 100 ml of water and slowly stirring in 5 g of arsenious oxide, which dis­
solves with heating in about 30 minutes. Next, 6.25 g of cupric sulfate was dissolved in I80 ml
of water and heated to about 90 °C. Adding the sodium arsenite solution precipitated the cop­
per arsenite, which was redissolved in dilute acetic acid (15% v/v). The resulting solution was
gently boiled and then cooled, at which point the bright green salt of the acetoarsenite (emerald
green) separated out. This was filtered, washed in hot water, and dried.

RECIPE 28 EMERALD GREEN, GMELIN'S RECIPE 1
Emerald green was synthesized using Gmelin's (i965) recipe 1 as follows: In a three-necked flask
of about 250 ml capacity and equipped with a thermometer and stirrer, 7.8 g of neutral verdigris
was dissolved in 100 ml of water, and the solution was heated to 70 °C. With stirring, 7.8 g of
arsenious oxide was added, which took about 10 minutes. The solution was heated to boiling

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