32 MANUAL OF GENEEAL AGBICULTUKE. 



(b) Test the standard sample and then 20 grams 

 each of several samples of alkali soils as follows: Place 

 filter paper in a funnel and put the sand or soil on it ; add 

 20 c.c. of water and let it leach through into a beaker, then 

 divide the leachings into two equal parts. Divide one part 

 into fourths, dilute three of them with one, two and three 

 volumes of water respectively. 



1. Sodium Carbonate. Test the undiluted part, then 

 each diluted part with red litmus paper. The rapidity 

 with which the paper turns blue indicates the amount of 

 black alkali or sodium carbonate. If it quickly turns deep 

 blue it indicates an excessive amount; one-tenth of one 

 per cent or more. If it turns blue very slowly it indicates 

 a lesser amount. Save the original samples as a standard 

 of comparison for samples of soil and label each. 



2. Sodium Chlorid. Take half of the unused leach- 

 ings and test for common salt as follows: Add a few 

 drops of nitric acid and then a drop or two of a 1.7 per 

 cent solution of silver nitrate, a white curdy precipitate 

 of silver chlorid, shows an excessive amount of salt (two- 

 tenths of one per cent or more) and from this we may find, 

 in testing soils, all amounts down to a trace which gives 

 only a slight milkiness on the addition of silver nitrate. 



3. Sodium Sulphate. Take the remainder of the leach- 

 ings and test for sodium sulphate as follows : Add a few 

 drops of hydrochloric acid, heat, then add a few drops of 

 barium chlorid to the hot solution. Transfer to the phos- 

 phoric acid tube and in the case of the prepared sand 

 mark the height of the column of precipitate which is 

 barium sulphate. This indicates a content of three-tenths 

 of one per cent, which is an excessive and injurious 

 amount. With this as a standard we may calculate the 

 amount of sodium sulphate in soil samples. (Record the 

 sodium sulphate mark as before, to be used as a standard.) 



