APPLE POWDERY MILDEW AND ITS CONTROL. P5 
PREPARATION OF THE IRON-SULPHID MIXTURE. 
The following directions are for the preparation of sufficient 
stock iron-sulphid mixture to make 500 gallons of spray: Fill a 50- 
gallon barrel about two-thirds full of water. Weigh out 10 pounds 
of iron sulphate (copperas), place in a sack, and suspend in the 
water. The iron sulphate will dissolve fairly rapidly, and when it 
is all in solution measure out carefully 2} gallons of commercial 
lime-sulphur solution testing 33° Baumé, or 2 gallons and 3 pints 
of a lime-sulphur solution testing 32° Baumé. Slowly pour all but 
2 pints of the lme-sulphur solution into the iron-sulphate solution 
in the barrel, stirring the mixture vigorously with a hoe or shovel. 
The addition of the lime-sulphur solution will produce a bulky, 
black precipitate, and when all but 2 pints of the lime-sulphur solu- 
tion has been added the mixture should be allowed to stand for a 
few minutes, when the black precipitate will begin to settle and 
a little of the clear liquid at the top can be carefully dipped out 
with a clean glass or cup. This clear liquid will probably show no 
yellow lime-sulphur color, which means that an excess of lime- 
sulphur solution has not yet been added. In other words, there is 
still some iron sulphate in solution, in which case the addition of a 
drop of lime-sulphur solution to the clear liquid in the glass will 
produce a black precipitate. This means that more lime-sulphur 
solution should be added to the stock in the barrel, and about 
half of the remaining 2 pints should now be poured in and the 
contents of the barrel stirred vigorously and allowed to stand. Some 
of the clear liquid should again be dipped off and tested as before, 
to determine whether an excess of lime-sulphur solution has been 
added. If necessary, the addition of small quantities of lime-sul- 
phur solution should be continued until some of the clear liquid 
dipped from the top, after the contents of the barrel have been 
well stirred and allowed to settle, shows a pale yellowish lime-sul- 
phur tint. The purpose of using a slight excess of the lime-sulphur 
solution is to insure all the iron sulphate being utilized. The volumi- 
nous black precipitate that is formed consists of iron sulphid, pre- 
cipitated sulphur, and calcium sulphate. After a slight excess of 
lime-sulphur solution has been added, the barrel should be filled 
with water and the contents stirred thoroughly and allowed to stand 
for several hours. The black iron-sulphid mixture will settle into 
the lower half or third of the barrel, and the clear liquid should be 
poured off by carefully and gradually tipping the barrel, without al- 
lowing any of the black precipitate to run out. The barrel should 
again be filled with water, the contents thoroughly stirred and al- 
lowed to stand several hours, and the clear liquid poured off as before. 
