AGRICULTURAL CHEMISTRY AGROTECHNY. 505 



A simple, exact, and reliable method fox- the quantitative determination 

 of lead in drinking water, C. Reese and J. Drost {Gsndhts. Ingcn., 31 {1014), 

 l\'o. S, pp. 129-13S). — x^fter discussing the faults of the various methods hitherto 

 proposed for estimating the amount of lead in water, a colorimetric method Is 

 suggested. It consists essentially in noting the color produced in a volume of 

 water (previously evaporated with concentrated hydrochloric acid and again 

 made up to volume with distilled water) with hydrogen sulphid. A comparison 

 is made with tubes containing a known amount of acetic acid solution, lead 

 nitrate of known strength, and hydrogen sulphid. 



Estimation of iodin, especially in organic substances, R. GrUtzner (Chem. 

 Ztg., 38 (1914), No. 12, pp. 169, 110; ahs. in Jour. Chem. Soc. [London], 106 

 {1914), ^0. 621, II, pp. 513, 514). — A known quantity of the substance is mixed 

 with powdered sodium hydroxid. moistened and dried, sodium or barium 

 peroxid is added, and the mixture is incinerated. After cooling, a small quantity 

 of charcoal is added and the mixture is heated again. Tlie fused mass wliicli 

 results is then dissolved in water and filtered. If barium peroxid is used the 

 solution can be treated with carbon dioxid and sodium sulphate before filtra- 

 tion. The resulting alkaline solution is boiled after the addition of a little 

 crystalline potassium permanganate and talcum, acidified with sulphuric acid, 

 boiled, rendered alkaline, and boiled again after adding alcohol. The mixture 

 is filtered while hot, the excess of alcohol being expelled by boiling the filtrate, 

 which is then rendered slightly acid with a mixture consisting of sulphuric 

 and phosphoi'ic acids. Ammonium sulphate is added, the mixture boiled for 

 three minutes, cooled, and the iodic acid titrated after the addition of sulphuric 

 acid and potassium iodid. Six atoms of iodin are thus liberated and when 

 titrated they correspond to one atom of iodin in the original substance. 



Colorimetric estimation of creatin, E. Baur and G. TRiJMPLEK {Ztsclir. Un- 

 tersuch. Nahr. u. Genussmtl., 21 {1914), No. 10, pp. 691-113, figs. 3; ais. in 

 Jour. Chem. 8oc. [London], 106 {1914), No. 621, II, p. 595).— An investigation 

 of Jaffe's method for the estimation of creatin as regards the influence of time, 

 temperature, and concentration of acid on the conversion of creatin into 

 creatinin. 



It was found that in the case of meat extracts the creatin is converted com- 

 pletely when 10 gm. of the extract is heated with 100 cc. of normal hydrochloric 

 acid for four hours at 97° C. The estimation of creatin in meat extracts Is 

 carried out as follows : 



" Ten gm. of the extract is dissolved in water to give 100 cc. of solution ; 5 

 cc. of this solution is then treated with 15 cc. of saturated picric acid solution 

 and 5 cc. of 10 per cent sodium hydroxid solution. After seven minutes the 

 mixture is diluted to 500 cc, and the coloration compared with that exhibited 

 by a definite depth of twice-normal potassium dichromate solution. The result 

 gives the quantity of pre-formed creatinin. A second portion of 10 gm. of the 

 sample is then heated with hydrochloric acid as described above; after cooling, 

 5 cc. of the solution is neutralized, treated with picric acid and sodium hydroxid, 

 diluted to 500 cc, and the coloration compared. The amount of creatin plus 

 creatinin is thus obtained. The comparisons should be made while the solu- 

 tions are at a temperature of 17°. Liebig's meat extract was found to contain 

 from 3.72 to 0.76 per cent of creatinin and from 2.09 to 5.5S per cent of 

 creatin. Meat extracts prepared by the authors (1 kg. of flesh yielded 30 to 

 35 gm. of extract) contained from 7.5 to 8.9 per cent of creatin plus creatinin." 



Flours, starches, bread, alimentary pastes, and pastry, M. Akpin {Farines 

 Fdcules et Amidons, Pain, Pates Alimeniaires, Patisseries. Paris: C. B6ranger, 

 1913, XIII +190, pis. 8, figs. 9).— The book includes methods of analysis of 

 these substances, the interpretation of the analyses, and legislation in regard to 



