AGRICULTURAL CHEMISTRY — AGROTECHNY. 709 



pigment was formed. The name suggested for the enzym particularly active is 

 " homogentisinase.' 



Some experiments with tyrosinase obtained from the potato, beet root, and 

 the latex of Euphorhia lathyris are also reported. 



Oxidases of the female corn bloom, G. Doby {Math, ^s Term. Tud. /Jrtcsito, 

 Magyar Tud. Akad. [Budapest], SO ili)12), No. 2, pp. 824-339, figs. 2; abs. in 

 Ztschr. Gesam. Qetreidew., 4 {1912), No. 5, p. 139; Chem. Abs., 7 {1913), No. 1, 

 p. 106). — The fact that the female inflorescence turns brown after pollination 

 is said to be due to the presence of a peroxidase and an oxygenase. Peroxidase 

 is present only as a reserve enzym, acts in conjunction with the oxygenase, and 

 probably hastens the withering of the organs of the flower when they become 

 superfluous. 



The microscopical examination of vegetable products as an adjunct to 

 their chemical analysis, A. L. Winton {Orig. Commun. 8. Intemat. Cong. 

 Appl. Chcm. [Washington and New York], 18 {1912), Sect. VIIIc, p. 361-366; 

 Amer. Jour. Pharm., 85 {1913), No. 3, p. 182-137) .—This discusses why it is 

 necessary for the food and drug analyst to have a knowledge of botany, espe- 

 cially vegetable histology. 



The colorimetric method for determining hydrocyanic acid in plants with 

 special reference to Kafir com, C. K. Francis and W. B. Connell {Jour. 

 Amer. Chem. Soc., 35 {1918), No. 10, pp. 1624-1628) .—'' Th\& work on a method 

 for the determination of hydrocyanic acid was prompted by the need for an 

 accurate knowledge of the amount of hydrocyanic acid, or glucosids containing 

 hydrocyanic acid, that might be found in Kafir corn, milo maize, Johnson grass, 

 and other plants. In work done relative to the amounts of hydrocyanic acid 

 in the saccharin and nonsaccharin sorghums, it api^ared that there existed no 

 satisfactory method for the estimation of the small percentages of hydrocyanic 

 acid found in plants. These percentages may vary between 0.0018 and 0.03 

 per cent." 



After reviewing critically the silver nitrate, ferro-ferricyanid, ammonia- 

 alum, lead acetate, mercurous nitrate, and thiocyanate (colorimetric) methods, 

 the last-named with some modifications was decided upon as the most suitable 

 for this purpose. The procedure adopted was as follows: 



" In order to render the hydrocyanic acid in the sorghum available, triturate 

 50 gm. of the finely chopped material with 100 cc. of water; wash into a 1-liter 

 distilling flask with 100 cc. of water. Acidify with 50 cc. of concentrated sul- 

 phuric acid and distill about 150 cc. into 50 cc. of a 4 per cent solution of 

 potassium hydroxid. Care should be taken that the end of the condenser dips 

 into the potash solution at all times, or a loss of hydrocyanic acid may result. 

 Make the potash solution to a volume of 250 cc. and use an aliquot equal to 

 one-fifth of the entire solution. To this aliquot add 1 cc. of yellow ammonium 

 sulphid and evaporate to dryness on a water bath. Take up with 10 to 15 cc. 

 hot water and barely acidify with dilute hydrochloric acid. Filter through 

 quantitative filter paper until free sulphur is removed. Add i cc. dilute hydro- 

 chloric acid and boil 5 minutes. Filter to remove free sulphur; repeat the last 

 operation of boiling and filtering until the solution is absolutely clear. Make 

 up nearly to the mark in a 50-cc. Nessler tube and add 15 drops of 5 per cent 

 ferric chlorid solution. The presence of cyanid in the sample is indicated 

 by a bright cherry-red coloration. If too much acid is present the solution will 

 be lemon-yellow. If alkaline, the iron will be precipitated, but this condition 

 may be corrected by the addition of a few drops of acid. The exact quantity 

 of potassium cyanid present is determined by matching the color with stand- 

 ards in a colorimeter. The standard solution is made to contain 15 gm. of 



