228 AGRICULTURAL ANALYSIS 



five times its weight of sodium carbonate and fused with the 

 precautions given in standard works on quantitative analysis. 

 The fused mass is digested in water, boiled, and filtered, and the 

 residue washed first with boiling water and afterwards with am- 

 monium carbonate. The filtrate contains all the fluorin as sodium 

 fluorid, and, in addition to this, sodium carbonate, silicate and 

 aluminate. The filtrate is mixed with ammonium carbonate and 

 heated for some time, replacing the ammonium carbonate which 

 evaporates. The silicic acid and aluminum hydroxid which are 

 formed, are separated by filtration and washed with ammonium 

 carbonate. To separate the last portions of silica from the fil- 

 trate, add a solution of zinc oxid in ammonia. Evaporate until 

 no more ammonia escapes and separate by filtration the zinc 

 silicate and oxid. Determine the silica in this precipitate by dis- 

 solving in nitric acid, evaporating to dryness, taking up with 

 nitric acid and separating the undissolved silica by filtration. 

 In the alkaline nitrate the fluorin may be estimated by the usual 

 method as calcium salt. 



200. Estimation of Lime. The following is the Glaser-Jones 

 method, as practiced by Chatard in the Geological Survey: 88 

 One hundred cubic centimeters of the solution (containing one 

 gram of the original substance) are evaporated in a beaker to 

 about 50 cubic centimeters ; 10 cubic centimeters of dilute sul- 

 furic acid (one to five) are added; and the evaporation is con- 

 tinued on the water bath until a considerable crop of crystals 

 of gypsum has formed. The solution is allowed to cool, when 

 it generally becomes pasty, owing to the separation of additional 

 gypsum, and 150 cubic centimeters of 95 per cent, alcohol are 

 slowly added, with continual stirring, and the whole is allowed 

 to stand for three hours, being stirred from time to time, filtered, 

 with the aid of a filter-pump, into a distillation flask, and the 

 crystalline precipitate washed with 95 per cent, alcohol. The 

 filter, with the precipitate, is removed from the funnel and in- 

 verted into a platinum crucible, so that, by squeezing the point 

 of the filter, the precipitate is made to fall into the crucible, and 

 the paper can be pressed down smoothly upon it. On gentle 



M Transactions of the American Institute of Mining Engineers, 1892-93, 

 21 : 168. 



