AGRICULTURAL CHEMISTRY AGROTECHNY. 411 



and weighed. The amount of fatty acids can then be elicited by subtracting 

 from the weight obtained 0.01907 gm. for every cubic centimeter of one-half- 

 uornial potassium hydroxid solution used for neutralization. 



Determ.ination of acids in oils and fats, H. Loebell {Seifensiedcr Ztg., 38 

 {1911), Xos. W, pp. 501, 502; 20, pp. 530^532, fig. 1; Cliem. Ztg., 35 {1911), No. 

 31, pp. 276, 277; ahfi. in Ghcm. ZenthL, 1911, I, No. 19, pp. 1J,52, lJ/53; II, No. 3, 

 p. 163, fig. 1). — In this method from 5 to 15 gm. of fat is melted, if necessary, 

 and vigorously shaken with 2.5 cc. of alcohol. Fifty cc. of water and from 2 

 to 3 drops of a 1 per cent phenolphthaleln solution are added and titrated with 

 a decinormal sodium hydroxid solution until the color ceases to disappear. The 

 tlask is then vigorously shaken and titrated with decinormal hydrochloric acid 

 until colorless. 



Estimation of free fatty acids in fats, E. Bodtker (Cfiem. Ztg., 35 {1911), 

 No. 61, p. 5-'f8; ahs. in Analyst, 36 {1911), No. Ji2J,, p. 355). — A description of 

 the method noted above, which is deemed of special value for colored fats as 

 the dyestuCfs are insoluble in water. 



The determination of glycerin in fats and soaps, A. Beythien et al 

 {Ztschr. Untersuch. NaJir. u. Genussmtl., 21 (1911), No. 11, pp. 673-675).— The 

 Benedlkt-Zsigmondy method, as modified by Allen,* is deemed an accurate and 

 convenient method for determining glycerin. If, however, other substances are 

 present in the fat or soap under examination which are oxidized to oxalic acid 

 by an alkaline permanganate solution the acetin method must be employed. 



A new method for detecting dioxydiamidoarsenobenzol (Salvarsan), J. 

 Abei.in {Miinchen. Med. Wohmchr., 58 {1911), No. 19, pp. 1002, i003).— The 

 mthod is as follows : A small amount of Salvarsan is dissolved in from 2 to 

 3 cc. of water and from 3 to 4 drops of hydrochloric acid are added until the 

 solution appears colorless. The solution is then cooled under running water 

 and from 3 to 4 drops of a 1 per cent sodium nitrite solution are added, whereby 

 a diazo body is produced which has a greenish, yellowish fluorescence. A 10 

 per cent solution of resorcin made alkaline with sodium carbonate is now added 

 dropwise to the above solution, as a result of which a red coloration is produced. 



The method can also be applied to detecting Salvarsan in the urinary secre- 

 tion. 



The determination of alkali in arsenical dip fluid, L. Cohen {Jour, and 

 Proc. Roy. Soc. N. 8. Wales, J,J, {1910), pt 1, pp. 77-79).— "The determination 

 of alkali in dip fluid by direct titration against standard acid is complicated by 

 the presence of tar and finely divided foreign matter from the hides of the 

 cattle, which it is impossible to separate by filtration, and the black color of 

 which precludes the use of an indicator, except in the form of test paper. If 

 litmusi paper is used, the carbon dioxid and perhaps also the arsenious acid 

 Indicate an acid reaction before all the sodium carbonate is neutralized ; it 

 consequently gives results a good deal too low." 



The method proposed is as follows : " To 50 cc. dip fluid in a small beaker, 

 run in 5 cc. normal sulphuric acid from a burette, stir, filter at once through 

 dry paper, take 10 cc. filtrate with a pipette, transfer to a beaker, and dilute 

 with about 100 cc. water. The solution is now colorless. Add 2 drops methyl 

 orange solution (cochineal is entirely imsuitable, being rapidly bleached by the 

 arsenic) and titrate to neutrality with decinormal NaOH. The end reaction 

 will be found perfectly sharp. Calling n the number of cubic centimeters deci- 

 normal NaOH used, and p the number of grams Na2C03 per 100 cc. of dip fluid : 

 p=.053X(10-H «)•" 



1 Benedikt-Ulzer : Analyse der Fetto, 1908, .'5. ed., p. 197. 



