344 
Remarks. —This solution was taken as the standard with which the others are 
compared, although it injured the leaves and necessitated a dilution to 2 gallons. 
The excess of ammonia necessary to dissolve the carbonate was probably the cause 
of the injury. The grading was not upon the injury, but only as regards the dis¬ 
ease. The manner in which this solution spreads and adheres is well known and 
forms a basis for comparison. The treated rows were graded - 1 and 1, or no better 
than adjacent untreated rows, on September 2 and 5, and 1 better on October 13. 
No. 5.— CUPRIC FERROCYANIDE MIXTURE. 
(Rows 5 and 5 1 .) 
14.90 grams cupric sulphate (CuS0 4 , 5H 2 0). 
22.35 grams potassium ferrocyanide (yellow prussiate of potash) K 4 FeCy 6 , 
3H 2 0. 
1 gallon of water. 
Chemical notes. —A well-defined chemical compound, with the formula Cu 2 Fe 2 Cy fi , 
with possibly CuK ferrocyanide present (see Watts’ Dictionary, /. c., 1889, p. 325). 
Thereactions, however, were not obtainable. It is used ordinarily as a delicate test 
for the presence of Cu in solution. According to observations of Miss E. A. South- 
worth, spores of Cladosporium fulvum grew luxuriantly in drops of water contain¬ 
ing this precipitate. The normal reaction would be as follows: CuS0 4 ,5H 2 0-f- 
K 4 FeCy 6 , 3H 2 0=CuFeCy 6 +K 4 S0 4 -f 8IDO. This would indicate that the substance 
sprayed upon the plants was a combination of copper ferrocyanide and potassium 
sulphate. 
Remarks. —This fungicide is more difficult to prepare than ammonical solution, 
but covers the foliage as well and adheres about as well. It proved scarcely more 
effective, but did not injure the foliage. The treated rows were 1 and 0 grades better 
than the adjacent untreated rows on September 2, and 14 and 0 on October 13. Fur¬ 
ther tests are necessary with a stronger mixture to settle the fungicidal value of this 
preparation 
No. 6.— CUPRIC HYDRATE, BLACK, MIXTURE. 
(Rows 6 and 6 l .) 
14.90 grams cupric sulphate (CuS0 4 , 5H 2 0). 
14.90 grams potassium hydrate (KHO) (caustic potash). 
1 gallon of water. 
The cupric sulphate and the potassium hydrate in concentrated solutions were 
mixed and allowed to stand until the mixture became black. Theu the whole was 
made up to 1 gallon. 
Chemical notes. —According to Prescott and Johnson (Qualitative Chemical Anal¬ 
ysis, 4th ed., 1891, pp. 86-87), the combination formed when CuS0 4 and KHO are 
allowed to stand in contact is represented by the formula Cu 3 0. 2 (0H).2 if the solu¬ 
tions are both concentrated and the KHO is added to saturation. The normal reac¬ 
tion of the two substances as given above will be CuS0 4 5H 2 0-{-2KH0 = Cu 
(H0) 2 -f-K 2 S0 4 -f-5H 2 0. In the substance sprayed upon the plant there is, therefore, 
a combination of copper hydroxide and potassium sulphate. 
Remarks. —This mixture is more difficult to prepare and does not cover or adhere 
to the foliage so well as ammoniacal solution. It proved more effective in retarding 
the progress of the disease and did not injure the foliage. The treated rows were 4 
and 1 grades better than adjacent untreated rows on September 2, and and 0 on 
October 13. It is a mixture possessing no particular merit, and is markedly inferior 
to the hydroxide Nos. 7 and 8, but should be tried stronger. 
NO. 7.— CUPRIC HYDROXIDE MIXTURE. 
(Rows 7 and 7 1 .) 
14.90 grams cupric sulphate (CuS0 4 , 5H 2 0). 
29.80 grams potassium hydrate (KHO). 
1 gallon of water. 
Prepared in the same way as No. 6, but applied before turning to the hydrate. 
