98 MASS. EXPERIMENT STATION BULLETIN 252 



pectin extracts were tested, of which fruit pectin proved of no value; agar- 

 agar, at the rate of 0.024 to 0.048 per cent, probably some; Iceland moss 

 (Cetraria), less and not dependable; and Irish moss (Chondrus), of no 

 value. The mucilaginous extracts were slightly more promising: — no in- 

 crease in suspension was obtained with licorice (Glycyrrhiza) ; slight in- 

 crease, with 0.080 to 0.160 per cent of linseed (Linum), both flaxseed 

 meal and the fat extracted residue; considerable increase, with 0.016 to 

 0.160 per cent of quinceseed (Cydonia); and slight increase, if any, with 

 slippery elm (Ulmus). Miscellaneous extracts from corn stover, hay and 

 rye straw, used at the rate of 0.801 to 1.603 per cent, increased suspen- 

 sion appreciably; but to ascribe their action to definite compounds would 

 be difficult. Glycerol was of no value. Of the proteids, neither gelatine 

 nor glue increased suspension. In subsequent tests, 0.10 per cent of 

 albumen, casein, gelatine and glue with Bordeaux 4-4-50, using chemical 

 hydrated lime, did not increase suspension. Albumen and casein would 

 not disperse satisfactorily in water. 



Various organic acids — butyric, citric, gallic, lactic, pyro-gallic, tannic 

 and tartaric acids — were employed, of which tannic acid at the rate of 

 0.016 to 0.080 per cent improved suspension. Salts of organic acids, such 

 as calcium caseinate, sodium albuminate, benzoate, caseinate, oleate and 

 resinate, gave no increase. Several of these substances were laboratory 

 prepared and probably carried an excess of sodium hydroxide. Castile 

 and resin soaps were of no apparent value, but soap powder at the rate 

 of 0.016 to 0.801 per cent increased suspension. Soaps are objectionable, 

 however, in that they react with lime on standing to form a curdy pre- 

 cipitate. 



Of the inorganic substances, calcium and magnesium silicates and alu- 

 ininum hydroxide proved of no value, but liquid sodium silicate at the 

 rate of 0.032 to 1.603 per cent, increased suspension. The dry silicate 

 was less effective. Bordeaux so treated, however, tends to peel from the 

 leaves on drying (Dunbar). Bentonite, clay, fuller's earth, infusorial earth, 

 Perkin's earth, talc and Wilkinite were also employed. Of these, 0.016 

 to 0.160 per cent of Bentonite and 0.048 to 0.160 per cent of Wilkinite 

 proved of value. These are yellow "ball" clays of similar characteristics, 

 and with fungicides, other than Bordeaux with excess lime, may serve to 

 increase the visibility of the spray residue. 



The results obtained with the more promising supplements affecting 

 suspension are reported in Table 1. 



Tannic acid, Bentonite and Wilkinite were the most dependable sub- 

 stances employed for increasing the suspension of Bordeaux mixture, al- 

 though quinceseed extract, soap powder and sodium silicate deserve men- 

 tion. Other substances may prove serviceable under different conditions 

 or in larger amounts; but whether their use with a more highly dispersed 

 lime is warranted, is an open question and depends somewhat on other 

 considerations such as ability to increase wetting, spreading and adhesive- 

 ness and to retard decomposition. Lovett (58) claims that suspension in 

 itself is a fair indication of power to spread, and most workers will con- 

 cur in principle. The substances reported may prove of value with other 

 copper fungicides but probably not to the same degree. 



