NOTES AND ABSTRACTS. 



523 



time before Bordeaux mixture begins to be effective. This is often a 

 great disadvantage, and it can be obviated by using only just sufficient 

 lime to precipitate all the copper in the first instance, no basic calcium 

 sulphate being then contained in the precipitate. As lime dissolves in 

 water to the right extent to make a Bordeaux mixture of very nearly 

 normal strength clear lime-water should be used instead of milk of lime. 

 To make 100 gallons of wash 6 lb. 6^ oz. of copper sulphate are dissolved 

 in water in a wooden vessel, and to it are added 86 gallons of clear 

 lime-water, the whole being made up to 100 gallons by the addition of 

 soft water. The lime-water is obtained by putting about 5 lb. of good 

 quick-lime in 120 gallons of soft water, which, after being stirred several 

 times, is allowed to settle. It is most important that the mixture should 

 be tested to make sure that all the copper has been precipitated, and this is 

 best done by putting a few drops of a solution of potassium ferrocyanide 

 in a white saucer containing some water and dropping into it some of the 

 clear liquid obtained after the Bordeaux mixture has settled, any brown 

 or red coloration indicating copper in solution, a danger to be rectified by 

 the addition of a little more lime-water, after which the test should be re- 

 peated, bearing in mind that any excess of lime above the minimum required 

 weakens the mixture and represents direct loss of money, the excess to 

 lime being no preventive of scorching, but possibly even the cause of if 

 (p. 103). The stain produced on a steel knife is not a safe enough test. 

 This method of preparation reduces the cost of Bordeaux mixture by 

 three-fifths without in any way diminishing its effectiveness. An appendix 

 to this Report contains a paper by Mr. Pickering on " The Chemistry of 

 Bordeaux Mixture." — A. P. 



Bordeaux Mixture. By C. S. Crandall (U.S.A. Exp. Stn., Illinois, 

 Bull. No. 135). — An account of laboratory and field experiments to 

 elucidate the manner in which soluble copper is liberated from Bordeaux 

 mixture, and to investigate the causes of injury due to Bordeaux mixture. 

 The history and preparation of the mixture are given, with the various 

 opinions held as to its chemical nature and fungicidal action. 



Bordeaux injury occurs in two forms — brown spots and margins of the 

 leaves, and yellowing of the leaves with their subsequent fall. Their 

 appearance is very irregular, especially the latter form, and is not always 

 due to Bordeaux mixture. Browning of the leaves was produced by 

 spraying with dilute copper sulphate solutions and by their injection into 

 the stem. Yellowing, except in one case, was not produced by these 

 means. 



Sprayed trees showed slightly more injury when exposed to the 

 weather than when protected from rain and dew. Great injury resulted 

 from the use of air- slaked lime in making the mixture. 



The report contains an elaborate series of analyses of drip- water 

 from sprayed trees. Soluble copper was found in this water seven days 

 after spraying, and continued to be present throughout the season. 



The amount of free lime (alkalinity) diminished day by day. In 

 about one month there was no alkaline reaction. The presence of this 

 free lime did not prevent the solution of the copper. Rain and dew were 

 more effective in liberating the copper than artificially applied water. 



