1917] AGRICULTURAL CHEMISTRY — AGROTECHNY. 205 



The effect of the amino acids as produced by digestive proteolysis on the 

 amylolytic enzyms is indicated. The work is being continued. 



Quantitative microscopy, T. E. Wallis {Analyst, U (1916), No. 489, pp. 357- 

 375, fig. 1). — The author points out the common errors in the microscopical 

 examination for adulteration, and describes a method of general applicability 

 wiilch obviates the usual sources of error. As a standard for comparison in the 

 new procedure, the author uses a suspension of lycopodium spores. 



An improved method of determining solubility, W. S. Hendrixson {Proc. 

 Iowa Acad. Set., 23 {1916), pp. 31-3 Jf, figs. 2). — A simple procedure for deter- 

 mining solubility, in which the solution is stirred by air wliich has been 

 previously saturated with moisture at the temperature for which it is desired 

 to determine the solubility, is described in detail. This saturation of the air 

 compensates for the usual unavoidable loss by evaporation when the stirring 

 is accomplished by air. The apparatus was used in connection with solubility 

 determinations of acid sodium and acid potassium phthalates, which have been 

 proposed by the author as standards in acidimetry and alkalimetry (E. S. R., 

 34, p. 408). 



Preparation of sulphurous acid, E. Habt {Jour. Amer. Chem. Soc, 30 

 {1917), No. 3, p. 376). — For the preparation of small amounts of sulphurous 

 acid for the laboratory the author recommends the warming of fuming sulphuric 

 acid containing 30 per cent SOa with sulphur. Lump sulphur in not too large 

 amount should be used. It dissolves in the acid and forms a blue solution from 

 which, on warming, SOj mixed with some SO3 is given off. If SOa is objection- 

 able, the gas obtained can be absorbed, and the resulting solution boiled to 

 obtain the SOj. The acid which remains is still fit for most uses. The value 

 of the procedure, in view of the saving in copper, is considerable. 



An improved nephelometer-colorimeter, P. A. KoBEai {Jour. Biol. Chem., 

 29 {1917), No. 2, pp. 155-168, figs. 9). — The construction and manipulation of 

 the new instrument, together witli a simple and convenient lamp and lamp 

 house, are described in detail. Advantages claimed for the new apparatus 

 are a screw arrangement for changing the heights of the liquids, and, therefore, 

 the elimination of lost motion inherent in racks and pinions ; the elimination 

 of dark cloth curtains ; black one-piece glass plungers ; fused one-piece nephelo- 

 metric and colorimetric cups ; and a convenient eye support. 



The iodometric determination of sulphur dioxid and the sulphites, J. B. 

 Febquson {Jo4ir. Amer. Chem. Soc., 39 {1917), No. 3, pp. 36^-373).— The author 

 briefly reviews the methods which have been used, and points out a number 

 of sources of error. 



For the very accurate determination of large or small amounts of sulphur 

 dioxid the excess iodin method is recommended. When carbon dioxid and 

 sulphur dioxid are to be determined in the same sample the sulphite method 

 can be used to advantage. For the most accurate results it is indicated that 

 the following conditions must be observed : 



" The gas sample must not come in contact with even a trace of moisture 

 prior to its reaching the absorbent. The analyzing apparatus must be free from 

 all rubber connectors when exact analyses of mixtures containing 10 per cent 

 or more of sulphur dioxid are desired. For very accurate work it would be 

 better to dispense with them entirely, although this source of error for mixtures 

 containing less than 3 per cent of sulphur dioxid may be neglected. Mixtures of 

 sulphur dioxid and air when dry do not react appreciably, but when moist a 

 slow oxidation takes place. For this reason it is impossible to recover from 

 a moist container, even by pumping, the initial amount of sulphur dioxid if 

 the gas mixture has been in the container for any great length of time." 



