12 EXPERIMENT STATION BECORD. 



the flask. After five to ten minutes the flask is detached from the pump and 

 the mixture acidified with 30 per cent nitric acid. The blue color appears at 

 once. Where only traces of hydrocyanic acid are present it is sometimes neces- 

 sary to warm to about 50° in a water bath before the color appears. The sus- 

 pension is then diluted to a volume that would give a color density convenient 

 to compare with a suspension of Prussian blue made from a known weight of 

 potassium cyanid. 



"As a standard we used a suspension of Prussian blue made from 1 mg. of 

 potassium cyanid. Such a suspension diluted to 25 cc. gave a color of con- 

 venient density. For comparison we u.sed a Duboscq oohirimeter. 



" If the cyanid solution to be tested was sufliciently concentrated so that 

 further evaporation was unneces.sary, the test could be made in a test tube. We 

 kept the air out by means of a stopper and rotated the tube only enou;:h to mix 

 the reagents, allowing the mixture to stand five to ten minutes before acidifying. 

 Much shaking must be avoided to prevent excessive oxidation of the ferrous 

 hydroxid. . . . 



"The maximum quantity of Prussian blue can be obtained from a cyanid 

 only when the volume of the .<;ohitlon to be tested is sufficiently small, as has 

 been indicated by P>erl and Delpy and by Lander and Walden. In the test for 

 a cyunld It Is better to acidify with nitric or sulphuric acid than with hydro- 

 chloric, since an excess of the latter tends to pnnluce a green color. Any con- 

 siderable exce.ss of ferric .salts should Im» avoidetl In testing for a cyanid. 

 Application of heat Is not necesjyiry In testing for a cyanid by the metho<l 

 descrlbe<l. The presence of certain salts, particularly potassium fluorld, In the 

 liquid to be teste«l. has proved to be of great advantage. The methixl furnishes 

 a very delicate qualitative test for the presence of a cyanid. The method Is 

 suitable for the estimation of very small quantities of a cjanld In distillates. 

 The test as descrlln^l herein can be applle<l mlcrochemlcally to sections of 

 cynnogoiiotic plants." 



Examination of tomato pulp, W. I). Bioetx)w and F. F. Fitzoekai.d {Jour. 

 Indus, and Kngin. Chan., 7 (1915), No. 7, pp. 602-606) .—Tomato pulp Is pr«^ 

 pared In large quantities for the manufacture of ketchup and pulp. While the 

 greater part of the pulp placed on the market Is made from whole tomatoes, 

 there are a number of plants that manufacture pulp from trimming stock In 

 connection with the canning of tomat«ws ; It accordingly becomes Important to 

 be able to dlstingui.sh the two kinds of pulp by a lalxiratory examination. As 

 the result of this Investigation a basis was found whereby differentiation could 

 be acconipIish(^l. 



If the specific gravity or index of refraction of the filtrate prepared from the 

 pulp of unknown origin and the percentage of .solids In the pulp by drying do 

 not agree with the relation between the determinations given In a table In- 

 cluded In the text, It may be assumed that the sample under examlnatlou was 

 not prepared from whole tomatoes, or that some other substance, such as salt, 

 has been a»lde<l. Moreover, trinunlng stcx^k pulp rarely conforms to the rela- 

 tions found In whole tomato pulp. For Instance, the Insoluble solids are usually 

 higher and the acid lower. 



A descriiitlon of the method used In the Investigation Is given. 



The judging of milk. C. J. Konino and W. C. Mooi.t, Jr. (Chem. Weckhl.. 

 11 (1914), No. 24, pp. 51&~550, flgg. .j).— This discusses the variations In thr» 

 milk constituents and physical characteristics as Influenced by temperature, re- 

 moval of the animal from the barn or pasture, change of feed. Individual pecu- 

 liarities, estrutn. milking i»ersonnel. thoroughnoss of milking, dl.'»eas«>s. calving, 

 Insufilcicnt «lrlnklng water, time of taking water, flies, and unknown ca»isos. It 

 also demonstrates the value of certain tests (fat. specific gravity, total solids. 



