4 BULLETIN 
The results of their laboratory tests, in which the re-formed copper 
sulphate was determined after carbon dioxid had been passed through' 
the various basic sulphates, led Bedford and Pickering to believe that 
the Formula A spray, re-forming 40 per cent of the copper sulphate, 
was from 12 to 15 times as effective as ordinary Bordeaux mixture 
(Formula D), which re-formed 2.8 per cent of the copper sulphate, 
and that the Formula C spray, re-forming 22 per cent of the copper 
sulphate, was about 8 times as effective as the standard Bordeaux 
(Formula D) . 
These investigators (4) stated also that, "the efficacy of a fungicide 
must not be estimated by the amount of copper contained in it, but 
by the amount which becomes soluble and therefore available for 
fungicidal action. Nor should the efficiency of a spray be judged by 
the visible deposit left on the leaves, for even if it were composed 
entirely of copper compounds it does not follow that it would be 
more efficacious than some other deposit which might be invisible. 
In most cases the deposit consists largely of material which is quite 
inefficient and may be detrimental to fungicidal action, as is the lime 
which constitutes four-fifths of the deposit visible after spraying with 
ordinary Bordeaux mixture." Later they reported that the idea 
that the fungicidal action of standard Bordeaux spray does not com- 
mence until several days after its application had been definitely dis- 
proved, and that the effects of the application of Bordeaux do not 
become visible at once because time is necessary for the decay of the 
tissues, which is the case even when a copper salt in solution is 
applied, but that the excess of lime in ordinary Bordeaux causes the 
fungicidal action to proceed more slowly. Pickering, however, be- 
lieved that in ordinary or standard Bordeaux made with milk of 
lime the copper reacts and undergoes on the tree the changes given 
under the reaction for Formula D (p. 3). 
Swingle (23), Sicard (22), Bell and Taber (5), Vermorel and Dan- 
tony (24), and others have discussed the chemical composition of 
standard Bordeaux sprays, which are prepared by mixing a solu- 
tion of copper sulphate with milk of lime. These two ingredients 
are brought together in various ways, and the manner of mixing 
undoubtedly affects the chemical and physical properties of the 
spray. The details of the many theories covering the chemical 
reactions which take place when copper sulphate and calcium 
hydrate are mixed need not be considered here. 
Opposed to the belief held by Pickering and others that the copper 
of Bordeaux is slowly made active by the carbon dioxid of the air 
are the statements by Lutman (14) that Bordeaux mixture is 
fungicidal immediately upon application. This writer considers that 
the lime particles in Bordeaux have fungicidal properties. Swingle 
(23), in 1896, advanced a series of ideas as to possible methods 
