AGRICULTURAL CHEMISTRY — AGROTECHNY. 613 



one and lies between 10-^ and 10*, and depends upon the lecithin preparation 

 under examination. Neutral salts were found to cause an even greater turbidity 

 of the suspension, but had the disadvantage of inhibiting the flocculating 

 process and changing the optimum. 



By mixing lecithin and protein together a new complex is produced which 

 at first flocculates very markedly but later causes only turbidity in the optimum 

 points for pure lecithin. This, according to the author, is the first time in 

 which it has been shown that a colloid, sensitive to an acid, may be influenced 

 .by the addition of another colloid. 



Estimation of minute amounts of arsenic in foods, E. Clark and A. G 

 Woodman [U. S. Dcpt. Agr., Bur. Chem. Circ. 99, pp. 7, figs. 3). — A modification 

 of the Marsh-Berzelius method as applied to the estimation of minute amoimts 

 of arsenic in foods is described. The method makes use of the form of ap- 

 paratus devised by Bishop for the determination of arsenic in sulphuric acid." 

 In the method standard mirrors are prepared for comparison. Antimony, when 

 present in the material under examination, must be removed before testing. 



Honey and its analysis, F. Muttelet (Ann. Falsif., 4 {1911), No. SO, pp. 192- 

 196). — This is- a bibliography of the literature in regard to the chemistry of 

 honey. See also a previous note (E. S. R., 25, p. 109). 



Examination of marmalades and milk chocolates, Habtel {Chem. Ztg., S^ 

 {1910), No. IJfl, p. 1256; ahs. in Chem. Ahs., 6 {1912), No. 6, p. 78i).— "The 

 author prefers to filter off the insoluble matter, wash, dilute the filtrate to a 

 definite volume, and analyze aliquot parts of this. For milk chocolate, the Baler 

 and Neumann method is recommended, also the determination of the Reichert- 

 Meissl number, which with a 10 per cent milk addition is 2.8 to 3, with 20 per 

 cent 5.6 to G." 



Cider vinegar, F. E. Mott {Jour. Indus, and Engln. ChenK, 3 {1911), No. 10, 

 pp. 747-750). — This is a description of a method which has for its purpose the 

 detection of certain forms of adulteration in cider vinegar which are being prac- 

 ticed at the present time. It depends upon the relation of levulose and dextrose 

 in pure cider vinegar as calculated from the percentage of reducing sugars pres- 

 ent, expressed as dextrose, and the polariscope reading in degi'ees Ventzke as 

 observed in the 200 mm. tube. 



The detection of benzoic acid in coffee extract, H. C. Lythgoe and C. E. 

 Marsh {Jour. Indus, and Engin. Chem., 3 {1911), No. 11, p. 842). — "Make the 

 solution acid and extract several times with ether. Wash the combined ether 

 extracts with water and extract with ammonia. Evaporate the ammoniacal 

 extract to a small volume, adding ammonia from time to time to prevent it from 

 becoming acid, and add a solution of manganese sulphate. Filter through a 

 small filter, wash with as little water as possible, and add ferric chlorid to the 

 filtrate, when a dark greenish precipitate will occur if benzoic acid is present. 

 Evaporate to dryness in the casserole in which the precipitation was made, and 

 sublime by placing an inverted funnel covered with a filter paper in the dish 

 and heating over an asbestos gauze. Remove the funnel and determine the 

 melting point of some of the crystals which, if benzoic acid, should be 121.4° C. 

 The rest of the crystals may be dissolved in ammonia, the excess of ammonia 

 evaporated and ferric chlorid added, when the characteristic flesh-colored pre- 

 cipitate will occur if benzoic acid is present. 



" For quantitative purposes the method of Edmund Clark ^ was employed 

 with good results, as the natural reacting substance has but little influence." 



"Jour. Amer. Chem. Soc, 28 (1906), No. 2, pp. 178-182. 

 "Science, n. ser., 30 (1909), No. 764, pp. 253, 254. 



