228 Pflanzenkrankheiten. — Bacteriologie. 



The crystallization of Bordeaux mixtures 1 : 1 or 1:0,5 is retarded 

 by the presence of such impurities as ferrous sulphate, calcic car- 

 bonate, magnesia oxide and magnesia carbonate; but this retardation 

 is not due to the diluent action of the salts in question. 



The crystallization of Bordeaux mixtures 1 : 1 and 1 : 0,5 may 

 also ceteris paribus be delayed by various inorganic substances, 

 Saccharose being particularly effective. 



Bordeaux mixtures after carbonization are slightly soluble in 

 pure water, and dissolve readil}'' in water containing carbon dioxyde 

 in Solution. 



Bordeaux mixtures are soluble in water containing ammonic 

 salts in Solution. 



Alkaline Bordeaux mixtures are soluble in dextrose, Saccharose 

 and other organic substances giving the biuret reaction. 



The physical State of the copper precipitate found in Bordeaux 

 mixtures is affected, irrespective of the ratio cupric sulphate to 

 calcic oxide, by: 



a. The dilution of the salts and the manner in which they are 

 brought together. 



b. The temperature of the water. 



After the cupric sulphate and calcic have been brought together 

 a slight delay in stirring the mixture does not materiallj^ affect the 

 physical State of the precipitate. 



Long continued stirring of Bordeaux mixture does not mate- 

 rially affect the physical State of the precipitate. 



The Bordeaux mixtures employed in practice, fall into one or 

 another of three types: 



a. "Neutral" Bordeaux mixtures of which Woburn Bordeaux 

 mixture is a true type and "acid" Bordeaux mixture a proximate type. 



b. Slightly alkaline Bordeaux mixtures. "Neutral" Bordeaux 

 mixture is a good example of this class. 



c. Strongly alkaline, or basic Bordeaux mixtures. In this class 

 belong those Bordeaux mixtures in which the ratio cupric sulphate 

 to calcic oxide is not greater than 2 to 1, 



M. J. Sirks (Haarlem). 



Ayers, S. H. and W. T. Johnson Jp., Ability of Colon 

 Bacilli to survive pasteuriza tion. (Journ. agr. Res. 

 Washington. III. p. 401—410. 1915.) 



The summary and conclusions, given by the writers, are as 

 follows: 



The thermal death point of 174 cultures of colon bacilli isolated 

 from cow feces, milk and cream, human feces, flies and cheese 

 showed considerable Variation when the cultures were heated in 

 milk for 30 minutes under conditions similar to pasteurization. 



At 60° C. the lowest pasteurizing temperature, 95 cultures or 54.59 

 per Cent, survived; at 62,8° C, the usual temperature for pasteurizing 

 12 or 6.89 per cent, survived. One culture was not destroyed at 

 65.6^ on the first heating, but in repeated experiments it was always 

 destroyed. 



There is a marked difference in the effect of heating at 60° C. 

 and at 62.8° C. Although there is only a diff"erence of 2.8° C, 87.3 

 per cent of the cultures, which survived at 60° C, were destroyed 

 at 62.8° C. 



Considerable Variation was found in the thermal death point 



