510 EXPERIMENT STATION" EECOED. 



slowness with which the Aarious liquids filter and the great difficulty in always 

 obtaining solutions sufficiently clear and free from small particles for polarizing. 

 The lead salts have a tendency to pass through the filter, especially with certain 

 types of fruit of low acidity. The chief cause of slow filtration is the presence 

 of pectin bodies, always present in fruit juices to a greater or less extent." 



The author has, therefore, modified the procedure as follows: 



"A weighed amount of juice, generally 100 gm., is placed in a 500 cc. beaker. 

 With vigorous stirring about two or three times the volume of 95 per cent 

 alcohol is added. . . . The liquid is decanted through a filter and the precipitate 

 washed twice with 95 per cent alcohol. The combined filtrates are then evapor- 

 ated in a current of air on the water bath to about 75 cc. After cooling, the 

 solution is made up to 100 cc. in a measuring flask, using 10 to 15 cc, of 95 per 

 cent alcohol and distilletl water. The temperature when the volume is finally 

 made up to the mark should be close to that at which the polariscope readings 

 are to be taken. This solution is then treated exactly as in the original method, 

 except that no clarification is necessary. ... In cases where the alcohol has 

 caused some fruit color to pass into solution the addition of a tiny drop of 

 bromin and vigorous shaking and filtering, if necessary, before reading will give 

 satisfactory results. . . . 



"Another advantage of this method of procedure is that concentration of the 

 original juice is possible. Two hundred gm. may be used, and the final volume 

 after evaporation made up as usual to 100 cc." 



The quantitative determination of formaldehyde by the ammonia method, 

 A. Beythien et al. (Ztschr. Untersuch. Nahr. n. Genussmtl., 21 {1911), No. 11, 

 pp. 671-673). — In view of the fact that various investigators have obtained 

 different results with the method when using different indicators (phenolph- 

 thalein, rosolic acid, methyl orange, cochineal, litmus, and Congo red), the 

 authors made a study of the methods, using the above-named indicators and 

 comparing the results with those obtained by the accurate iodin method of 

 Romijn (E. S. R., 9. p. 420). 



The Smith method." which uses rosolic acid, was found to yield the most 

 accurate results, while cochineal and methyl orange came next. Phenolph- 

 thalein, litmus, and Congo red could not be employed at all. 



Quantitative determination of formic acid, H. Franzen and F. Eggeb 

 (Jour. Prakt. Chem., n. ser., 83 (Wll), No. 6-7, pp. 323-325; ahs. in Jour. Soc. 

 Chem. Indus., 30 (1911), No. 9, p. 572).— This is a modification of the method 

 proposed by Franzen and Greve (E. S. R., 23, p. 11). 



The testing' of creosote, C. E. Sage (Jour. Soc. Chem. Indus., 30 {1911), 

 No. 10, pp. 5SS-59.fl, figs. 3). — The analysis of impure substances like commercial 

 creosote by different methods will yield varying results. The author, therefore, 

 describes in detail methods which he recommends for the examination of 

 cresotes intended for sheep dips, disinfectants, etc., with special reference to 

 British conditions. 



In regard to determining nicotin in tobacco extracts, J. Leistee {Chem. 

 Ztg., 35 {1911), No. 27, pp. 239, 240).— The high results obtained with the Ulex 

 method are deemed probably due to an improper rubbing up of the powder, as 

 this results in a retention of ammonia which finally finds its way over into the 

 distillate with the nicotin. The author has utilized the method for several years 

 with perfect satisfaction. With a sample of technically pure nicotin the follow- 

 ing figures were obtained : ITlex method S6.7 per cent, Kissling 87 per cent, and 

 Schloesing 91 per cent. 



"Amer. Jour. Pharm., 70 (1898), pp. 86-94, 



