52 N. S. ENTOMOLOGICAL SOCIETY 



water to copper sulphate solutions in gradually increasing a- 

 mounts, results in the formation of a series of basic sulphates 

 of copper. He states that by adding lime water to copper 

 sulphate solution just short of alkalinity, the final compound 

 present is 10 CuO, S0 3 , and this substance has been put on 

 the market under the name of "Woburn Bordeaux Paste." 

 On the other hand, the compound present in ordinary mix- 

 ture, made from equal weights of lime or copper sulphate, he 

 believes to be 10 CuO, S0 3 , 3 CaO in the presence of a large 

 excess of free lime. Pickering's claim of superiority for the 

 former compound is based on the fact that at the time of 

 application and for a short time thereafter, it shows infinite- 

 ly more copper in solution than mixtures containing an excess 

 of lime. 



Sicard has done further work along the same lines and in a 

 series of articles on the subject (9) he, in the main, corroborates 

 the work of Pickering and upholds the contention that Bor- 

 deaux mixture made without excess of lime must possess a high- 

 er fungicidal value than ordinary Bordeaux, made from equal 

 weights of both chemicals. In his researches he found that 

 when a pure milk of lime is poured into, and energetically stir- 

 red in, a solution of copper sulphate in the proportion of .1685 

 parts of the lime to one of the copper sulphate, the Bordeaux 

 mixture obtained is acid. Until this quantity is added the salt 

 formed is in the form of the basic sulphate of copper S0 2 , 3.5 

 CuO; with .1685 parts of lime to one of copper sulphate the 

 tetracupric sulphate, S0 2 , 4CuO results; with .180 parts, the 

 pentacupric sulphate. S0 2 5CuO; with .202 parts, the decacu- 

 pric sulphate, S0 2 5CuO; and with .225 parts, the double sul- 

 phate of copper and calcium, S0 2 , oCuO, CaO is formed. As 

 the proportion of lime is still farther increased double sulphates 

 of copper and calcium, richer in lime than the preceding, are 

 first formed and, as the proportion of lime is increased up to 

 four or five parts of lime to one of copper sulphate, double hy- 

 drates of copper and lime are obtained. All these compounds 

 contain water in proportions varying with the conditions of 

 preparation and the major part of them are united to definite 

 proportions of calcic sulphates. Sicard states that of all these 

 compounds, the tetracupric sulphate S0 2 , 4CuO, nH20, pos- 

 sesses the highest fungicidal value and in the preparation of 

 Bordeaux mixture, its production should be aimed at. If, as 

 Sicard believes, Bordeaux made with a great excess of lime con- 

 tains compounds differing chemically from those in the ordin- 



