SUPPLEMENTS FOR COPPER FUNGICIDES 97 



the suspension of Bordeaux mixture made from different batches of dry, 

 laboratory-prepared hydrated lime after being soaked over night. The 

 liydrate was not air-separated and undoubtedly was less uniform in com- 

 position and size of particles than many brands of chemical hydrated 

 lime. The relatively lower suspension of the resulting Bordeaux would 

 be expected to respond more readily to the influence of added substances. 

 Considerable variation is inevitable, however, due to inability to control 

 the reaction. Bordeaux 4-2-50 was adopted as preferable to that of a 

 higher lime content, and the amount of added substance (usually called 

 a protector) generally ranged from 0.008 to 0.160 per cent of the spray, 

 although larger amounts were occasionally employed. In the latter case 

 the mixtures were apparently less susceptible to other factors, but exces- 

 sive dilution of the spray residue is considered objectionable in that it 

 may reduce materially the effectiveness of the fungicide or in some in- 

 stances even the physiological activity of the plant. The added substance 

 was dissolved or dispersed as thoroughly as possible. With extractives the 

 coarse material was removed by screening. A poorly dispersed protector 

 tends to have an effect on the suspension of Bordeaux similar to that of 

 coarse particles of lime. In some instances the inherent properties may 

 be more than offset by poor dispersion. The solution of copper sulfate 

 was added to the soaked hydrated lime and then the protector added, 

 thoroughly mixed and suspension readings taken at the end of 1, 2 and 3 

 hours. These tests were conducted in rubber-stopjiered, glass museum 

 jars of the following dimensions: total height, 305. 5mm (14 inches); length 

 and outside diameter of the body, 303.0 by 63.5 mm (13.0 by 3.5 inches) 

 and capacity to the neck, 850 to 900 cc. The length of the colunm for 

 a volume of 780 cc was determined for each jar and the results calculated 

 in percentage. 



Among the substances tested were sugars, dextrin, starches, gums, gum 

 resins, soapbark extract, pectin extracts, mucilaginous extracts, miscel- 

 laneous extracts, glycerol, proteids, organic acids, salts of organic 

 acids, soaps, inorganic salts, earths, etc. The data are too vol- 

 uminous to permit their publication in entirety, but by excluding 

 most mixtures that settled more than 10 per cent an hour, a rea- 

 sonable tolerance, many of the substances are eliminated entirely and 

 only average results are reported on those retained. The averages do 

 not represent an equal number of tests. As a rule, the more promising 

 the results, the more determinations were made in confirmation. An in- 

 crease in suspension with an increasing amount of substance within limits 

 that are permissible, and the uniformitj' of results with a given amount, 

 were considered a criterion of the effectiveness of the substance employed. 



The sugars — dextrose, lactose, levulose, manitose and sucrose — did not 

 appear to have an appreciable influence on the suspension of Bordeaux 

 4-2-50 although occasionally a test with 0.016 per cent came within the 

 tolerance. Powdered dextrin, British gum, arrowroot-starch (Maranta), in- 

 ulin (Alant) and soluble starch (amylo-dextrin) did not increase suspen- 

 sion within the limits tested. Gum arable (Acacia), at the rate of 0.080 

 to 0.160 per cent may have had a slight influence, but tragacanth proved 

 less satisfactory although tests of 0.024 per cent were passable. Several 

 gum resins were employed but required a solvent and did not increase 

 suspension. 



Soapbark (Quillaja) extract containing saponin had no effect. Several 



