28 METHOD OF ANALYSIS 



Dilute to about 100 cc, if less than that volume, place a thermometer in the flask, 

 and heat to S5°C. Add 75 cc. of recently prepared molybdate solution [I, 4 (a) ], 

 digest in a water bath at 80°C. for 15 minutes, with occasional shaking, remove from 

 the bath and allow to stand at least 10 minutes before filtering. Continue the de- 

 termination as directed under I, 6 and calculate to phosphorus pentoxid (PsOt). 



28 CALCIUM CARBONATE REQUIRED.— TENTATIVE. 



Place 100 grams of soil, as prepared under 2, in a 400 cc. wide-mouthed bottle, 

 add 250 cc. of N/1 potassium nitrate, stopper, and shake continuously for 3 hours 

 in a shaking machine, or every 5 minutes by hand. Let stand overnight. Draw 

 off 125 cc. of the clear, supernatant liquid, boil 10 minutes to expel carbon dioxid, 

 cool, and titrate with standard sodium hydroxid solution, 1 cc. of which is equiva- 

 lent to 4 mg. of calcium carbonate (0.001% on basis of the weight of soil used), using 

 phenolphthalein as indicator. 



29 STATEMENT OF RESULTS.-OFFICIAL. 



Calculate all results of soil analysis as per cent of the soil dried to constant weight 

 as under 3 and state in the following order: 



Insoluble residue 



Soluble silica — 



Manganomanganic oxid (Mn304) 



Potassium oxid (K2O) 



Sodium oxid (NajO) 



Calcium oxid (CaO) 



Magnesium oxid (MgO) 



Ferric oxid (Fe203) 



Aluminium oxid (AI2O3) , 



Phosphorus pentoxid (P2O6) 



Sulphur trioxid (SO3) 



Organic carbon 



Inorganic carbon 



Volatile matter 



Total nitrogen 



Total phosphorus 



Total potassium 



Phosphorus soluble in N/5 acid 



Calcium carbonate required 



Total 



BIBLIOGRAPHY 



1 J. Am. Chem. Soc, 1904, 26: 294, 1640. 



2 J. Agr. Rci.,3: (II), 155. 



» J. Ind. Eng. Chem., 1914, 6: 465. 



* Fresenius. Quantitative Chemical Analvsis. Revised and amplified transla- 

 tion of the 0th German ed., 1906, 2: 1175; Crookes. Select Methods in Chemical 

 Analysis. 4th ed., 1005, p. 23; Wiley. Principles and Practice of Agricultural 

 Analysis. 1906, 1: 423; U.S. Geol. Surv. l?ull. 422, p. 171; Am. J. Sci., 2nd ser., 

 1871, 50: 269; Am. Chem., 1871, 1; Ann. Chem. Pharm., 1871, 159: 82. 



