AGEICULTURAL CHEMISTRY AGROTECHNY. 809 



reprecipitate with sodium acetate. Tlie precipitate is then titrated in a sul- 

 phuric acid solution with potassium permanganate. 



The method will yield very good results if no metals are present which form 

 complexes with the tartaric acids. If iron, aluminum, and antimony are pres- 

 ent, low results are obtained, but this error can be obviated if citric acid is 

 added. The method is deemed a good one for determining tartaric acid in 

 argols, yeast, wine, beer, and in pears. 



About a simple method of preparing lecithin emulsions, and the deter- 

 mination of their strength, J. C. Schippers (Biochcm. Ztschi:, 40 (1012), 

 No. 1-2, pp. 189-192; abs. in Zcntbl. Expt. Med., 1 (1912), No. 16, pp. 730, 

 731). — After describing the procedure for producing lecithin emulsions, the 

 author describes a method for determining their strength, as follows: Ten cc. 

 of the emulsion is addetl to a solution consisting of potassium bichromate 5 gm., 

 38 per cent hydrochloric acid 300 cc, and water to make 1 liter, and heated 

 carefully in a wide-mouthed stoppered bottle at 90° C. for 6 hours. After 

 cooling, 10 cc. of a 5 per cent potassium iodid solution is added, and 2 hours 

 later 30 cc. of water and titrated with twenty-fifth-normal sodium thiosulphate 

 solution. The indicator is a starch solution freshly prepared. 



The sodium chlorid solution used in preparing the emulsion is also titrated, 

 and the results obtained are subtracted from those gotten from the titration of 

 the lecithin emulsion. 



Investigations of the determination of dry substance in root crops, A. 

 Madsen-Mygdal and P. Christensen (Tidsskr. Landhr. Plantcavl, 19 {1912), 

 No. 3, pp. 453-532, figs. 2). — The investigations were conducted during 1907- 

 1912 for the purpose of studying the various factors that have a bearing on 

 the accuracy of the methods used in the determination of the dry substance in 

 different I'oot crops, esi)ecially mangels. There were considered in this con- 

 nection the method of sampling, treatment of the pulp, size of sample, period 

 and temperature of drying, changes in the composition of the pulp (especially 

 sugar) during the drying process, factors that influence the changes in the 

 sugar of the pulp, etc. 



The sugar in ruta-bagas and turnips was found to reduce copper hydroxid 

 and is probably invert sugar. The sugar in mangels in the fall is present as 

 sucrose, and only during the winter and toward the spring is hydrolyzed with 

 the formation of invert sugar. On continued drying the latter sugar is decom- 

 posed, this resulting in the formation of water or other volatile substances, 

 and introducing an error in the results obtained for dry. matter. Sucrose, on 

 the other hand, is not changed during the drying process, so that pulp of 

 mangels may in the fall be heated at from 05 to 98° C. for 24 hours. 



On the basis of the results obtained in the investigation, the authors give at 

 the close of the paper a detailed description of the method for determining dry 

 matter in roots. 



A word in regard to the nutrient salt question. — Determination of the 

 ash constituent of foods, R. Berg {Chem. Ztg., 36 (1912), Nos. 55, pp. 509-511; 

 56, pp. 523, 52.'f). — After pointing out some of the incongruities which appear 

 in the literature pertaining to the metabolism of the mineral constituents of 

 foods, the author gives his methods for the determination of ash and the indi- 

 vidual ash constituents. The methods given include iron, aluminum, calcium, 

 magnesium, phosphoric acid, potassium, sodium, chlorin, sulphuric acid, nitric 

 acid, and ammonia. 



Recommendations for the revision of the milk section in the Swiss food 

 book (MilcJnc. Zentbl, 4I (1912), Nos. 19, pp. 598-603; 20, pp. 630-632) .—This 

 deals with definitions of milk, methods of sampling, qualitative and quantitative 

 tests for examining milk, which include tests for preservatives, and bacterio- 

 iugical tests. 



