1. The addition of casein to the mixed lime sulphur-lead arsenate spray causes:
(a) an increase in the amount of soluble arsenic formed on the decomposition of the spray,
(b) no change in the reactions of the polysulphide sulphur.
2. The addition of lime to the spray:
(a) decreases the formation of soluble arsenical compounds,
(b) reduces the fungicidal value of the spray owing to its reaction with the sulphur liberated from the calcium sulphide.
3. The addition of lime-casein to the mixed spray is influenced by the composition of the lime-casein.
If much free lime is present:
(a) the formation of soluble arsenic is dependent on external conditions which in certain cases tend to decrease the amount of soluble arsenic formed,
(b) the fungicidal value of the spray is reduced as in 2 (b).
If slight excess of lime is present, or if the sample has badly carbonated:
(a) the amount of soluble arsenic is increased,
(b) there is little effect on the reaction of the polysulphide sulphur.
4. The addition of gelatine to the spray:
(a) increases the formation of soluble arsenic,
(b) has no effect on the reaction of the calcium sulphide.
5. The rate of decomposition of the mixed spray is retarded by the addition of casein, lime, lime-casein and gelatine.