THE MONTHLY BULLETIN. 271 



In reply, the propounder of the question wrote as follows: "My 

 field observations have certainly been that the efficiency of the com- 

 bination against red spider, for which the snlfnr fumes are essential, 

 is greatly less than that of lime-sulfur alone. We have not been able 

 to get any definite Hue on its fungicidal value.'' 



Considerable time has been devoted to the discussion of this topic of 

 lesser importance, ])ut it brings np so many questions of interest that 

 it is hoped the speaker may be pardoned for thus presenting the sub- 

 ject so much in detail. 



Emulsions-Bordeaux. A foreigu reference is at hand in which 

 this eoiuhination is reported to have been used with success. 



Soaps-Bordeaux. Soap has been recommended as an addition to 

 Bordeaux mixture to increase the spreading and adhesive (lualities of 

 the fungicide. Rosinous soaps are to be preferred as the copper 

 rosinate (insoluble copper soap) is more easily handled by the spray 

 machinery. No injurious effects to the foliage or fruit are to be antici- 

 pated witli this c()nil)ination. 



Tobacco-Bordeaux. This combination is advised against for tAvo 

 reasons: First, copper is a precipitant for nieotin and it is believed will 

 render the alkaloid inert; second, certain tobacco extracts, containing 

 much extractive matter, may have a solvent action upon the copper of 

 the Bordeaux mixture, and disastrous results mav attend its use, from 

 the burning effect of the dissolved copper. 



It is ((uite probable that the above remarks may also be applied to 

 Paris green-tobacco combinations, although it may be that the less 

 soluble Paris green would not be so susceptible to the action of tobacco 

 extracts. Time was not available to determine this point by laboratory 

 experiments in time for incorporation in this paper, nor was this com- 

 bination mentioned in the reports of experiments made with spray com- 

 binations which were reviewed. 



General Discussion of Soaps. In order to more fully understand 

 the effect of soaps aiul soap emulsions upon other spray materials, a 

 little of your time is asked to consider the composition of soaps. 



Soaps, as is well known, are made by simple mixture or by boiling 

 together either potash or soda lye with a fat or oil or rosin. We may 

 then consider the composition of the fats and oils rather briefly. 



The vegetable and animal fats and oils wiiich are suitable for making 

 soaps are rather complex compounds but for the purpose of this dis- 

 cussion may be considered to be composed of two important con- 

 stituents of opposite chemical characteristics: (1) Glycerin, which is 

 chemically known as a weak base, and (2) a fatty acid, the kind of 

 acid depending upon the kind of fat or oil. 



The lyes used in making soap are strongly basic compounds in which 

 the alkali metal (potassium or sodium) is the base. They may or may 

 not also have an acidic component. Bases possess different degrees of 

 chemical activity and may be strong or weak bases. The stronger bases 

 have the habit of replacing the weaker ones in a chemical compound. 

 Other causes than the above also have to do with the replacement of one 

 base by another, but to take up this would lead us too far from the 

 subject. The potassium and sodium bases are very strong bases while 



