New YorK AGRICULTURAL EXPERIMENT STATION. 25. 
When a solution of copper sulphate and the milk of lime are 
combined the resulting mixture is a saturated solution of calcium 
sulphate and calcium hydroxide holding in suspension in solid form 
copper hydroxide and calcium sulphate. While the semi-solid mass 
of the precipitate is gelatinous in character, it contains, as before 
stated, some granules and some crystals. The particles of solid 
matter are crystals of calcium sulphate, and after standing a short 
time crystals of copper hydroxide. Interspersed in the gelatinous 
mass are generally to be seen small, dark blue, irregular, spherical 
bodies. According to Schander*® these are small grains of uncom- 
bined calcium hydroxide which have been covered by fine particles 
of copper hydroxide. Schander holds that these bodies greatly 
diminish the action of the bordeaux mixture on the spores of fungi 
and lessen the adhesive power.. The particles can be avoided in 
part, the same writer asserts, by a slow and complete slaking of 
the lime or by slaking the lime and pouring it through a fine sieve. 
One important character of bordeaux mixture is agreed upon 
by all chemists; namely, that all but a trace of the copper is in the 
form of an insoluble precipitate. The clear liquid above this 
precipitate, which always forms when the mixture stands, has no 
value as a fungicide, the precipitate containing all of the fungicidal 
properties. The precipitate must therefore be kept in uniform sus- 
pension by agitation when spraying. 
When bordeaux mixture is exposed to the air marked changes 
at once take place. The excess of lime is changed by the carbonic 
acid in the air into carbonate of lime, forming as a crust on the 
surface of the superimposed liquid. When the lime has been 
transformed into calcium carbonate, the copper hydroxide is 
changed by the action of the air into copper carbonate. 
This change is greatly hastened by rain, dew or even a moist 
atmosphere if the mixture has been applied to foliage. When this 
change takes place in a considerable quantity of the mixture, the 
dirty, blue-green color hitherto mentioned is assumed. At the same 
time the precipitate becomes much more granular in character. | 
The greater the excess of lime, the slower the above changes 
take place; the greater the exposure to the air, the quicker the 
changes occur. Clark,®? Bain,?4 Schander,®* Swingle,?* and others 
state that substances secreted by the cells of the plant sprayed or 
* Schander (53, p. 519). 
Clarke 23, p243).<°- Bain (4, p. 93)0°> Schander (53, p. 578). ** Swingle 
(60, p. 21). 
