AGEICULTURAL CHEMISTRY — AGROTECHNY. H 



Estimation of aldoses. — I, The action of neutral sodium hypo-iodite, N. 

 Bland and L. L. Lloyd (Jour. Soc. Chem. Indus., S3 (1914), No. 19, pp. 948, 

 949). — The action of sodium hypo-iodite upon formaldelij'de was first studied. 

 It was found satisfactory for estimating formaldehyde but not for paraformal- 

 dehyde. The sugars studied were dextrose, levulose, sucrose, lactose, and mal- 

 tose. Only sugars containing an aldehyde group reacted wuth neutral hypo-iodite. 

 The results for dextrose varied from 96.4 to 99.7 per cent, average 98.8 ; for 

 lactose, 99.1 to 99.4, average 99.3; and maltose 99.9 to 101.8, average 100.2. 

 Sucrose (pure and chemically pure) when hydrolyzed gave a higher result, in- 

 creasing with the purity of the sucrose. 



Attempts are being made to apply the methods to the examination of starch 

 and dextrin products employed for sizing purposes. 



The production of w-hydroxy-cr-methylfurfuraldehyde from carbohydrates 

 and its influence on the estimation of pentosans and methylpentosans, Maky 

 Cunningham and C. Doree (Biochem. Jour., S {1914), ^0. 4, PP- 438-447)- — 

 " w-Hydroxymethylfurfuraldehyde is formed by the action of dilute hydro- 

 chloric acid on hexoses, starch, and the celluloses. Its amount varies from one 

 to two per cent. Owing to its slow formation, it does not interfere with tlie 

 accuracy of pentosan estimations made by the Krober phloroglucinol method, if 

 aniline acetate is used as the indicator. Its occurrence, however, renders pre- 

 viously made estimations of methylpentosan of doubtful value. It is probably 

 the unknown substance giving a precipitate with phloroglucinol referred to by 

 previous worliers, and its presence explains many of their observations." 



Determination of rhamnose in the presence of other methylpentoses, E. 

 VoTOcEK and R. Potme^il (Bui. Soc. Chim. France, 4- ser., 15-16 {1914), No. 

 13, pp. 634-639). — I^hamnose is converted into cyanhydrin by hydrocyanic acid, 

 and cyanliydriu when hydrolyzed yields 5-rhamno-hexonic acid, which is oxi- 

 dized with heat bj' nitric acid to mucic acid. On completion of oxidation the 

 solution is evaporated to one-third of its volume on a water bath and allowed to 

 stand for three days in the cold, the sides of the container being rubbed with a 

 glass rod at intervals. The crystalline mucic acid obtained is washed with a 

 little water, dried, and weighed, 45.5 parts of mucic acid representing 100 parts 

 of anhydrous rhamnose. When other methylpentoses are present, for instance 

 rhodeose, the mucic acid yielded is not so constant, but the method for this 

 purpose is considered satisfactory enough to estimate the molecular proportion 

 of rhamnose present in hydrolyzable glucosids. 



On the determination of small quantities of hydrocyanic acid, A. A^iehoevkb 

 and C. O. Johns {Jour. Amer. Chcm. Soc, 37 {1915), No. S, pp. 601-S01).—ln 

 some work on cyanogenetic plants it was found necessary to have a method 

 for estimating small quantities of hydrocyanic acid. The Prussian blue method, 

 when modified, was found to meet the demands of the work when certain 

 precautions are taken. 



" Before concentrating the hydrocyanic acid solution, as in the case of a dis- 

 tillate, the portion to be tested should contain a slight excess of free sodium 

 hydroxid. "We used 0.02 to 0.1 gm. This solution is then concentrated in a 

 round-bottom flask of 200 cc. capacity by using a vacuum pump and condenser. 

 The heat is supplied by immersing the flask in a water bath kept below 70°. To 

 avoid any loss by spattering the flask is fitted to the condenser by means of an 

 adapter such as is used in the Kjeldahl method for the determination of nitro- 

 gen. We concentrate until less than 1 cc. of liquid remains in the flask. 



" From 0.2 to 0.5 cc. of 3 per cent freshly prepared ferrous sulphate solution 

 and about 0.05 gm. of potassium fluorid are then added. The flask is exhausted 

 at once by means of a water vacuum pump. The contents are mixed by rotating 



