21 
The most practical remedy for the apple scab must be one that may 
be applied in the same water with Paris green or London purple with¬ 
out thereby endangering the foliage. It is the opinion of our station 
chemist, Dr. Babcock, that not only the ammoniacal copper carbonate, 
but the sodium hyposulphite and the sulphides of lime and potash, 
all tend to render the arsenic of Paris green and London purple soluble, 
and hence can not be wisely used in connection with these poisons. 
The copper carbonate, however, which in the ammoniacal solution is 
the beneficial agent in preventing the apple scab, does not have this 
effect when used without the ammonia. The question therefore arises, 
is the ammonia solvent necessary*? 
I have recently made some tests with a sample of commercial precipi¬ 
tated copper carbonate, and find that its state of division is such 
that it remains suspended in water rather better than Paris green, and 
so may be applied by any apparatus that successfully distributes the 
latter. It apparently adheres to the foliage nearly or quite as well, 
when applied in simple suspension, as in the diluted ammoniacal solu¬ 
tion. 
I recommend, therefore, that those who spray their apple trees for 
the prevention of injury from the codling moth, make the experiment 
in a portion of the orchard of adding the precipitated copper carbon¬ 
ate to the water, at the rate of an ounce to twenty-five gallons. No 
harm to the foliage can result from this measure, while we have every 
reason to expect that much benefit will accrue in the prevention of the 
apple scab. 
University of Wisconsin, Madison, Wis. 
THE COPPER SALTS AS FUNGICIDES. 
By F. D. Chester. 
In order to make an intelligent comparison between the several well 
known fungicides containing copper, it is important to understand 
what salts of copper occur in each and in what relative proportions. 
This in turn involves some inquiry into the chemical reactions which 
take place in their preparation and during their stay upon the vine. 
For much valuable assistance in the preparation of these notes I am 
indebted to Prof. C. L. Penny, the Chemist of this Station. 
THE BORDEAUX MIXTURE. 
Formula .—Copper sulphate, 6 pounds; lime, 6 pounds; water, 22 
gallons. In tbe addition of milk of lime to a solution of copper sul¬ 
phate, the lime in solution precipitates the copper as cupric hydroxide, 
forming at the same time a slightly soluuble sulphate of lime. These 
two salts, together with an excess of lime, remain in suspension in the 
Bordeaux mixture. 
