AGRICULTURAL CHEMISTRY AGROTECHNY. 805 



the investigation show that where 25 cc. of sulphuric acid is used in tlie method 

 15 gni. of sulphuric acid should remain behind. 



The amount of material to be taken for each determination is 3^ gm. for 

 cereals or a material containing much carbohydrate, while tlie limit for fat- 

 containing material should vary from 3 gm. for a sample containing from 5 to 

 10 per cent of fat and l.o gm. for material containing from 80 to 90 per cent. 

 The amount of acid should be proportionately increased when small amounts 

 of nitrogen are present. 



Determination of total potassium, in nainerals, C. J. Schollenbebgeb (Jour. 

 Indnti. and Engin. Vhcm., Jf (1912), No. 6, yp. .}.?(>, .'/J7, lig. 1). — When potassium 

 alone is to be determined the J. L. Smith method is long and tedious and the 

 modifications thereof leave much to be desired. The following metliod has been 

 used with success in the laboratory of the Ohio Station : 



"Proceed as in the regular Smith method for total alkalis until the filtrate 

 from washing out tlie alkalis from the fusion is obtained. To this add a 

 moderate excess of hydrochloric acid and evaporate to dryness on a steam bath, 

 remote from ammonia fumes. Take up with about 2 cc. of concentrated hydro- 

 chloric acid and 25 cc. of hot water, and filter through [an Amesl suction filter 

 into a 1.50 cc. beake)\ washing the large beaker and filter well. Add the proper 

 amount of hydrochloroplatinic acid fjiolulion, and evaporate on steam bath until 

 of a semisolid consistency. The large amount of calcium chlorid present 

 crystallizes out on cooling, but is readily soluble in acidulated alcohol. The 

 crystalline precipitate of the potassium chloroplatinate is washed with acidu- 

 lateil alcohol. Gladding wash, and SO per cent alcohol, on a filter designed 

 especially for this work. After drying to remove alcohol, the precipitate is 

 dissolved in hot water, the solution being received in a tai'ed platinum dish, 

 and after evaporation, dried and weighed." 



The Ames filter, which possesses several advantages over the Gooch crucible 

 filter for collecting and washing the potassium platinic chlorid, is described and 

 illustrated. 



Carbon dioxid: Its volumetric determination, L. T. Bowser (Jour. Indus, 

 and Engin. Client., .'/ (WEt), No. 3, pp. 20.3-205, figs. 2). — This is a modification 

 of the Minis method, and consists essentially of releasing the carbon dioxid 

 from the substance under examination by means of hydrochloric acid, absorbing 

 it in a strong alkaline solution, and measuring the absorbed gas by titration 

 with a standard acid solution with the aid of a suitable apparatus. The ap- 

 paratus is depicted, and consists of an Eiienmeyer flask holding a small sepa- 

 ratory funnel, a short Liebig condenser having an inner tube of very small 

 bore, and an absorbing tower. The absorbing tower consists of a glass tube 

 containing some glass beads for the purpose of dividing the carbon dioxid, and 

 10 cc. of potassium hydroxid solution (50 gm. of potassium hydroxid in 100 cc. 

 of solution) for absorbing the carbon dioxid. 



On the determination of carbon dioxid in soils, L. T. Bowser (Jour. Indus, 

 and Engin. Chem., .'/ (1912), No. .), pp. 265, 266). — The method described above 

 is considered especially adaptable to soils containing small amounts of carbon 

 dioxid, giving more consistent results than the method generally employed. 



Determination of sulphuric acid in the soil, P. de Sornay (Internat. Sugar 

 Jour., 13 (1911), No. 153, pp. 497-500; ahs. in Zentbl. Biochem. u. Biophys., IS 

 (1912), No. 4, P- 132). — The usual method for determining sulphuric acid in 

 soils is deemed inexact, especially if much aluminum and iron are present. 

 The following method is recommended for this purpose: 



Ten gm. of the soil is mixed with 1 gm. of potassium nitrate and 5 cc. of 

 water, dried on the sand bath, calcined, and treated with 25 cc. of hvdrochloric 



