MANUAL OF GENEEAL AGRICULTUKE. 31 



tate appears. Filter while hot, then add a drop of am- 

 monium chlorid and 1 c.c. saturated solution of oxalate of 

 ammonia. Transfer to the closed funnel and allow the 

 precipitate of oxalate of lime to settle. Suppose the pre- 

 cipitate forms a column 2 c.m. high. This would indicate 

 a content of 1% of carbonate of lime. With a file mark 

 the height of this column after verifying your result, 

 either by comparing with tests of others, or by repeated 

 tests. The height of this mark becomes the standard of 

 comparison for future tests. 



(b) Test samples of soil in a similar way as follows : 

 Place one gram of soil in a test tube. Add 1 c.c. 

 hydrochloric acid and heat until it just begins to boil. 

 Add strong ammonia until a permanent precipitate 

 appears ; filter while hot, add a drop of ammonium chlorid 

 and 1 c.c. of a saturated solution of oxalate of ammonia. 

 Transfer to the closed funnel and allow the precipi- 

 tate to settle. Calculate the per cent of lime by using a 

 millimeter rule. Our standard indicates a lime content of 

 one per cent. In a clay soil 1 to 2% is about right. In a 

 sandy soil three-tenths to five-tenths of one per cent is 

 good. Ten to fifteen per cent is an excess in any soil. 



30. DETERMINATION OF ALKALI. 



Materials: Sand, sodium carbonate, sodium chlorid, 

 sodium sulphate, filter and litmus paper, nitric acid, silver 

 nitrate solution, barium chlorid, and phosphoric acid tube. 



(a) Prepare a standard of comparison as follows: 

 To 20 grams of sand which has been treated with hydro- 

 chloric acid, add 4 c.c. of a solution made by dissolving 

 in 100 c.c. of distilled water 1 gram of sodium carbonate, 

 1 gram sodium chlorid and 3.3 grams sodium sulphate. 

 This gives a content in the soil of one-tenth of one per cent 

 sodium carbonate, two-tenths of one per cent sodium 

 chlorid (common salt), and three-tenths of one per cent 

 sodium sulphate. These are all excessive and harmful 

 amounts and a soil which contains as much of any is un- 

 suitable for ordinary crops. 



