1910] AGRICULTURAL CHEMISTRY AGROTECHNY. . 503 



the specific gravity of commercial liquid hydrocyanic acid testing from 70 per 

 cent to 100 per cent purity and upon the extent of variation of hydrometer 

 readings as affected by temperature, and tliese figures are given in the form of 

 reference tal)les, by means of which it is possible to determine the quality of a 

 liquid in a moment's time by tlie use of a hydrometer graduated either in specific 

 gravity or Baurae degrees. These data have made possible the construction of 

 a cyanometer, a hydrometer graduated directly in percentages of hydrocyanic 

 acid and provided with a simple table of temperature corrections. 



"A method of analysis has been selected and shown to give concordant results 

 within 0.2 per cent. The development of any color, usually yellow, or an odor 

 of ammonia may be taken as a warning of incipient decomposition of the liquid. 

 Factors and materials favoring decomposition are water in excess of 5 per cent ; 

 high temperatures ; residue from a decomposed liquid ; all alkalis, nitric acid, 

 sodium cyanid ; soap ; or contact with lead, commercial tin, impure zinc, solder, 

 cast-iron, or steel. The following metals were found to be highly i-esistant to 

 the acid, somewhat in tine order named : Aluminum, block tin, pure zinc, brass, 

 nickel, silver, and copper. Aluminum is the most promising material for the 

 construction of delivery drums. Brass fittings are permissible." 



An adiabatic bomb caloriineter, E. B. Holland, J. C. Reed, and J. P. Buck- 

 ley (Chem. and MctaUurct. Engin., 21 (1919), No. 4, pp. 190. 191, fig. i).— The 

 authors describe certain improvements introduced at the Massachusetts Experi- 

 ment Station in the construction, thermometers, and lens of an adiabatic bomb 

 calorimeter of the Berthelot-Mahler-Kroecker type. A diagram is given of the 

 calorimeter as modified. 



Electrical apparatus for use in electrometric titration, H. S. Roberts {Jour. 

 Amer. Chem. Soc, U (1919), No. 9, pp. 1358-1362, figs. 2).— The author points 

 out that the choice of apparatus for use in electrometric titration is very differ- 

 ent from that of potentiometric apparatus for other purposes owing to the fact 

 that the interest lies in relative rather than absolute values of the electro- 

 motive force developed during the titration, that the electromotive force fre- 

 quently changes sign, and that the apparatus must often be used in an atmos- 

 phere chai'ged with acid fumes. 



Two simplified potentiometers for use in electrometric titration are described 

 and illustrated, and suitable forms of galvanometers are mentioned. 



Indicator test papers, I. M. Kolthoff (Pharm. Weekbl., 56 (1919), No. 7, pp. 

 175-187; (lbs. in Chem. Abs., 13 (I'fJW), No. 15, p. 1689).— A study is reported of 

 the influence upon indicator papers of various factors such as the kind of paper 

 employed and its preliminary treatment with various reagents, the concentra- 

 tion of the solution used, the manner of testing, and the nature of the solution. 

 This is followed by a discussion of the possible uses of indicator papers, the 

 conclusion being drawn that their chief value is in qualitative analysis within 

 definite limits of H-ion concentration. 



A table is included of relative sensitivities of various indicator papers. 



A rapid hydrogen electrode method for determination of hydrogen-ion con- 

 centrations in bacterial cultures or in other turbid or colored solutions, 

 H. M. Jones (Jour. Infect. Diseases, 25 (1919), No. 3, pp. 262-268, figs. 2).— 

 A simple form of hydrogen electrode apparatus is described which is said to 

 allow rapid saturation with hydrogen gas and to be accurate to at least 0.01 

 pH. A technique combining the indicator and gas-chain method is outlined for 

 use when large numbers of determinations are to be made, as in bacterial cul- 

 tures. This consists of taking a portion (2 cc.) of each solution to be tested, 

 diluting with 4 cc. of distilled water, and after arranging the tubes in groups 

 with reference to their degree of turbidity, placing each group in separate rows 

 in test tube racks. Equal amounts of some indicator with a range of color 



