1918.] AGKICULTURAL CHEMISTRY AGROTECHNT. 805 



which it cfin be prepared all reeoniiiiend its use in place of the iodimetric 

 procedure." 



An optical method for the determination of malic and tartaric acids in 

 the same solutions, J. J. Willajian (Jour. Amer. Chem. Soc, 40 (1918), No. 

 4, pp. 69S-70Jf, fig. 1). — The method described is based upon the use of a given 

 set of conditions in constructing tables or curves with known amounts of pure 

 malic and tartaric acids, which curves can then be used for the determination 

 of unknown quantities of these acids. The combination of conditions to give 

 satisfactory results from the standpoints of accuracy, ease of manipulation, 

 and applicability to materials from varied sources was determined after a 

 study of the effect of various factors on the rotating power of solutions of 

 malic and tartaric acids. The method adopted is as follows : 



An amount of the sample that will probably furnish at least 0.1 gm. of 

 either acid and not more than 0.6 gm. of tartaric acid and 0.8 gm. of malic 

 acid is neutralized with approximately normal ammonium hydroxid, treated 

 with 2 volumes of 95 per cent alcohol, and the pectins filtered off on a Biichner 

 funnel and washed with alcohol. To the filtrate is added an excess of a 10 

 per cent barium acetate solution in .50 per cent alcohol and enough 95 per 

 cent alcohol to make 14 volumes to 1 of the original solution. The pi'ecipitated 

 barium salts are removed by centrifuging or by filtering on a Biichner filter. 

 The precipitate is transferred to a beaker with hot water, heated to boiling, 

 10 cc. of 20 per cent ammonium sulphate solution added, and the mixture con- 

 centrated on the steam bath to about 80 cc. volume and transferred to a 100 cc. 

 flask. After cooling, 6 cc. of glacial acetic acid is added and the contents made 

 up to the mark with water. It is then filtered or centrifuged and two 25 cc. 

 aliquots of the clear solution are treated, respectively, with 10 cc. of 8 per cent 

 uranium acetate solution, and 10 cc. of 10 per cent ammonium molybdate solu- 

 tion. After standing in the dark for three hours, the solutions are polarized 

 in a 2 dm. tube at about 20° C. The two readings are then referred to the 

 graph and the amounts of malic and tartaric acids computed. 



As some of the reagents and conditions may be difficult to duplicate in some 

 laboratories the author recommends that each worker adopt conditions and 

 reagents as near as possible to those listed and then standardize his procedure 

 against known amounts of malic and tartaric acids. The factors likely to be 

 subject to change in different laboratories and which can be safely changed, 

 provided they are incorporated in the above standardization, are the kind of 

 light used with the polariscope, the length of time of standing before polariza- 

 tion, the temperature at which the polarization is made, and the purity of the 

 uranium and molybdenum salts used as activators. 



The method is said to be applicable for all products containing d-tartaric 

 or ?-malic acid, or both. Highly colored solutions can be worked with only 

 after decolorizing Math bromin and neutralzing the hydrobromic acid formed 

 with ammonia. 



The deterioration of raw cane svigar: A problem in food conservation, 

 C. A. Beowne {Jour. Indus, and Enc/in. Chcm., 10 {1918), No. 3, pp. 178-190, 

 figs. 15). — The results of chemical and mycological investigations on the dete- 

 rioration of raw cane sugar are reported. 



Periodic analyses of sugars showed that the so-called factor of safety, 



— where W is the percentage of water and S the percentage of sugar, 



100 s, 



should be about 0.3. If sugars are to be kept where the temperature maximum 



exceeds 20° C, only such sugars should be selected as have a factor of safety 



below 0.3. Where sugars of low factor deteriorate, the explanation may be 



