804 EXPERIMENT STATION RECORD. [Vol. 41 



essentially iu oxidiziup; the citric acid in acetic acid solution with potassium 

 permanganate, and treating the acetone thus formed witli ammonia and an 

 alcoholic solution of iodin to form iodoform. The technique for the pro<^edure 

 with fruit juices, milk, and various salts of citric acid is described. In the 

 cases of fruit juices and milk a preliminary treatment is necessary, which 

 consists in adding alcohol, filtering, and adding barium acetate to the filtrate 

 to form barium citrate. This is then treated with acetic acid, potassium 

 permanganate, etc., as noted above. 



Volumetric method for the determination of salicylic acid in the presence 

 of salicylic aldehyde, R. Beeg (Chem. Ztg., 43 (1919), No. 32-3S, p. 129).— The 

 method described depends upon the fact that colorless solutions of salicylic 

 aldehyde develop a strong citron yellow color on the addition of traces of alkali, 

 and that this color disappears on the addition of a weak acid such as carbonic 

 acid. 



The ether solution of the substance to be tested is shaken 3 times mth N/20 

 sodium carbonate solution and then wash'ed 3 or 4 times with water. If the 

 last wash water on the addition of a drop of N/20 sodium hydroxid remains 

 colorless, sodium carbonate must be added again. When the reaction is com- 

 plete, the combined extract is titrated with N/20 sulphuric acid until colorless, 

 warmed to allow escape of carbon dioxid, and titrated with N/20 sodium 

 h.vdroxid until the yellow color is again produced. The amoimt of salicylic 

 acid a. is calculated from the formula a=(<— [?i—t-.) ] X 0.0669, t being the 

 immber of cubic centimeters of sodium bicarbonate, ti of sulphuric acid, and t2 

 of sodium hydroxid employed. 



The electrical conductivity of milk, J. H. Coste and E. T. SheXboubn 

 (Anahjst, U {1919), No. 518, pp. 158-164, fins. 2).— An investigation of the effect 

 of certain factors upon the electrical conductivity of milk is reported and sum- 

 marized as follows: 



The temperature coeflicient of electrical conductivity in the region of 15° C. 

 is 0.000093, or about 2.3 per cent of the total conductivity. The electrical con- 

 ductivity of presumably genuine milks may vary from Ki5=0.0035 to 0.0047, 

 but in more than 50 per cent of the 200 or more samples examined it was be- 

 tween 0.004 and 0.0042. The electrical conductivity of milk increases up to a 

 certain point with the development of acidity, but reaches an almost constant 

 value while the amount of acid is still increasing. There is no well defined 

 correlation between electrical conductivity and total solids or total ash. but a 

 marked correlation between the electrical conductivity and the chlorin content 

 of milk. The specific conductivity of a mixture of milk and water decreases 

 with dilution, but that of the milk in the solution increases greatly as the 

 dilution increases .owing probably to dissociation of phosphates and citrates. 



In explaining these conclusions the authors refer to the work of Jackson and 

 Ilothera (E. S. R.. 33, p. 203), in which the results of measurements of the 

 electrical conductivity, percentage of milk sugar, and dejiressiou of the freezing 

 point of milk are interpreted from a physiological viewpoint. 



The authors conclude that the value of the electrical conductivity of milk is 

 not sufficiently well defined to make the determination generally useful for 

 detecting adulteraticm. " It would, however, be useful in a large dairy or 

 institution as a check on watering of milk which had already been examined 

 by the conductivity method, and which had afterwards passed through various 

 hands." 



Table for sorting of milk samples, L. J, Harris {Analyst, 43 (1918), No. 512, 

 pp. 315-311, fig. i).— A table, calculated from Richmond's formula T=0.25G-f 

 1.2F-I-0.14, is given which is said to enable the analyst to determine at a glance, 

 knowing the specific gravity and total solids of the sample, whether it is above 



