AGRICULTURAL. CHEMISTRY — ^AGROTECHNY. 807 



formaldehyde may be estimated with a fair approach to accuracy by Shrews- 

 bury and Knapp's method." 



Some other proprietary preservatives are also considered. 



The estimation of lime and potash in the ash of cereals, F. Thompson and 

 H. H. Morgan, Jr. (Jour. Indus, and Engin. Chcm., S (1911), No. 6, pp. 398- 

 ffOO). — ^Analyzing the ash in corn and wheat by the official method (E. S. R,, 

 20. p. 512) was found to yield unsatisfactory results, and existing methods 

 were also found not rapid enough. Methods were therefore devised for calcium 

 oxid and potassium oxid. 



P'or calcium oxid the following method is recommended : " Fifty cc. of the 

 hydrochloric acid solution of the ash, corresponding to 0.5 gm., are heated to 

 boiling, made slightly ammoniacal, and then acidified again with acetic acid, 

 adding about 10 cc. of 50 per cent acetic acid in excess, making the total volume 

 not more than 75 cc. The precipitate is boiled for a few minutes, allowed to 

 settle, and the combined phosphates of iron and aluminum filtered off and 

 washed thoroughly with hot water. Since this precipitate is usually very small 

 a reprecipitation has not been found necessary. About 10 cc. of saturated 

 ammonium oxalate solution are added to the filtrate while still hot and the CaO 

 determined in the usual way, either by ignition or titration with permanganate." 



The method for potassium oxid consists in neutralizing the hydrochloric acid 

 solution containing 0.5 gm. of ash with sodium hydroxid acidifying again 

 with acetic acid, boiling " the solution, and washing the precipitate of iron and 

 aluminum phosphates filtered off thoroughly with hot water. The filtrate is 

 concentrated to about 75 cc. and allowed to cool. Twenty-five cc. of cobalti- 

 nitrite solution, made according to the method of Adie and Wood (E. S. R., 

 12, p. 18), is now added. After standing over night at the room temperature 

 the material is filtered on an asbestos felt in a Gooch crucible, and washed 

 several times with cold 10 per cent acetic acid and finally once with cold water. 

 The asbestos and the precipitate are transferred with water to a small beaker, 

 and 40 cc. of a saturated Ba(0H)2 solution added and heated to boiling, when 

 a copious precipitate of cobaltic hydroxid will be formed. The precipitate is 

 allowed to settle and while still hot filtered into a 200 cc. graduated flask, wash- 

 ing thoroughly with hot water, cooled, and made up to 200 cc. 



" Measure off 25 cc. of standard i>ermangauate solution into a casserole, add 

 5 cc. of 1 : 1 H2SO4 and 150 cc. of hot water and run in the alkaline nitrite solu- 

 tion slowly from a burette until the color disappears. 



"On the basis of the formula K2NaCo(N02)e,H20, 1 cc. of tenth-normal per- 

 manganate is equivalent to 0.0007S5 gm. K2O. It has, however, been found to be 

 more convenient to use a permanganate solution of such strength that 1 cc. is 

 equivalent to 1 mg. of K2O, which would be 0.1274 normal." 



Determination of starch in brewers' grains, C. Kreuzee (Ztschr. Oesam. 

 Brauw., 3!^ {1911). Nos. 23, pp. 277-280; 2If, pp. 290-293; ahs. in Analyst, 86 

 (1911), No. 427, pp. 500, 501). — As none of the methods so far published gives 

 an accurate determination of the amount of starch present in brewers' grains, 

 the author proposes the following one for this purpose : 



"An average sample of the grains is ground as finely as possible in a Seek 

 (cutting) mill, and 2.5 gm. of the powder are mixed thoroughly with 10 cc. of 

 water. Twenty cc. of sulphuric acid of specific gravity 1.7 are then added, with 

 stirring, and, after the lapse of 15 minutes, the mixture is rinsed into a 100 cc. 

 flask with sulphuric acid of specific gi'avity 1.3, this acid being used to dilute 

 the whole to a volume of 100 cc. after 5 cc. of an 8 per cent phosphotungstic 

 acid solution have been added. The contents of the flask are now shaken, 

 filtered through a double filter, and 50 ce. of the filtrate are cooled in a stop- 



44616°— No. 9—12 2 



