228 TWENTY-FIFTH ANNIVERSARY REPORT. 
HOW TO DETECT IMPURITIES IN, COPPER COMPOUNDS. 
While the help of a chemist is needed to tell how much copper 
a substance contains, a few suggestions may be given which will 
enable anyone to test, in a rough way, samples of copper sulphate, 
and copper carbonate as well as paris green, in regard to their 
purity. 
1. Copper sulphate, if pure, should dissolve completely in warm 
water, making a clear solution, free from sediment or suspended 
matter. A solution of copper sulphate should form a clear solu- 
tion when treated with a sufficient amount of strong ammonia. 
2. Copper carbonate, if pure, should dissolve completely in nitric 
acid. It should also dissolve completely, or nearly so, in strong 
ammonia used in considerable quantity. 
3. Paris green should, if pure, dissolve completely in strong am- 
monia used in liberal quantity. 
A SPRAYED-GRAPE SCARE. 
In September, 1891, the New York city board of health Saeed 
and destroyed large quantities of grapes on the ground that they 
had been sprayed with copper compounds and were dangerously 
poisonous. Samples of clusters of grapes were selected which were 
covered with the largest amount of bordeaux mixture obtainable 
from those vineyards from which the condemned grapes came. 
Analysis showed that in each pound of grapes (the berries) there 
was about one-thirtieth of a grain of copper carbonate. To get an 
amount of copper that would be regarded as serious, if taken in 
one dose, one would need to eat not less than 3,000 pounds of grapes, 
skins included. Or, stated in another way, if one were to eat each 
day one pound of the worst sprayed grapes, including the skins, 
and if all the copper taken in this way were to accumulate in the 
body, it would require over eight years to accumulate an amount 
of copper which would, if taken at one dose, be considered dan- 
gerous, not necessarily fatal. 3 
THE COMPOSITION OF COMMERCIAL SOAPS IN 
RECA TION“ O SPRAYING. 
An investigation was undertaken to ascertain why commercial 
whale-oil soaps in some cases fail to destroy insects and in some 
cases cause injury of foliage (Bulletin No. 257, 1904). 
A soap is made by treating a fat or oil with an alkali, as caustic 
soda or potash. A soap is a chemical compound formed by the 
union of an alkali and the fatty acid or acids contained in a fat 
