202 EXPERIMENT STATION RECORD. 



show that solidification tal^es place from about 6 to S" C. below the meltiiifr 

 point. Also, previous to solidification the thermometer falls to from 10 to 12° 

 below the melting point. This characteristic property is common to all mixtures 

 of solid and liquid glycerids but does not hold good for mixtures of solid and 

 liquid fatty acids. The tallows used in all the observations contained free 

 fatty acids and therefore free gycerin, and whether small amounts of these 

 modify the solidifying point and are the cause of low zeros or erratic " rises " 

 is being investigated. 



The solidifying point of mutton tallow. — II, R. Meldbtjm {Chem. Neics, 

 111 {1915), No. 2883, pp. 98, 99; abs. in Jour. Soc. Chem. Indus., 34 (1915), No. 

 6, p. 288). — " Solid glycerids were separated from mutton tallow by treatment 

 with ether, and their solidifying point determined by Dalican's method, the 

 mass being melted at 80° C. and stirred while cooling from 55 to 47°, and the 

 thermometer then fixed at 1.5 in. from the bottom of the tube. The solidifying 

 point ranged from 49.7 to 51°, with a rise of from 3.4 to 4°. The presence of 

 suspended matter and the method of stirring had no influence on the results, 

 and no secondary stationary point was observetl. Erratic variations of the 

 'zero' solidifying point (i. e., the temperature to which the thermometer falls 

 before the rise commences) and of the rise were much smaller in the case of 

 the solid glycerids than of the original tallow, this being attributed to the in- 

 fluence of the greater proportion of liquid glycerids in the latter. Such varia- 

 tions do not occur with mixtures of stearic and oleic acids. Fluctuations of 

 the melting points of glycerids appear to be due to errors of manipulation, while 

 the solidifying point is influenced by the spee^l of crystallization. Constant 

 results are obtained when a constant amount of substance crystallizes per unit 

 of time. Glycerids require supercooling to start rajiid crystallization, and each 

 glycerid appears to have a specific ' zero ' point of incipient solidification. When 

 glycerids (especially mixtures of solids and liquids) are supercooled, the latent 

 heat of fusion may be insufficient to raise the temperature of the mass to the 

 normal solidifying point." 



The presence of an amino group in wool, K. Gebh.vbd {Farbcr Zlg., 25 

 (1914), No. 14, pp. 279-283; ahs. in Jour. Soc. Chem. Indu.'i., 33 (1914), No. 17, 

 p 856). — The author found that when wool was treated with formaldehyde, as 

 described by Kann," it still retained its power of reacting with nitrous acid to 

 form a true diazo compound. Wool probably contains two substances, an amino 

 acid and a colloidal substance loosely attached to the amino group of the acid. 

 It is thought that Kann, who maintains that wool does not contain an amino 

 group, probably split ofl; and coagulated the colloid, leaving the amino acid free 

 with an active amino grou]). 



Nephelometry (photometric analysis). — I. History of method and develop- 

 ment of instruments, P. A. Koeer and Saba S. Graves (Jour, //i/f ».«. and Engin. 

 Chem.. 7 {1915). No. 10, pp. 843-847. figs. 10). — A general review of the subject. 



A modified method for determining carbon-free ash. in plant substances, 

 G. E. BoLTZ (Jour. Indus, and Engin. Chem., 7 (1915), No. 10. pp. 859. 860).— It 

 is claimed that the usual method for determining ash in plant substances gen- 

 erally introduces an error, due to the presence of carbon dioxid in combination 

 with bases present. This is especially true of an ash containing large amounts 

 of calcium, magnesium, and potassium. A procedure which has proved very 

 satisfactory is as follows : 



" Weigh from 2 to 10 gm.. depending upon the material, into a platinum dish. 

 Ignite over a low flame until most of the carbon is burned off. Cool, cover the 

 dish with a watch glass and add through the lip of the dish about 20 cc. of hot 



Farber Ztg., 25 (1914), No. 4, pp. 73-75. 



