82 fJnie jReqiiirciiieiifs uf t'crlaiii Soils 



Immcndorff (8) employed a method for indicating lime reserves in 

 the soil, in which 2-5-10 grins, of the soil are boiled for half an hour with 

 200 c.c. of distilled water and 25 c.c. of sulphuric acid (N/5), the liquid 

 being then filtered and a back-titration made. Where it is a question 

 of ascertaining the amount of easily soluble alkaline earths irrespective 

 as to whether these are present as carbonates or silicates the method is 

 said to give useful results. 



Sestini (9) suggests the use of boiling acetic acid and Mayer (lU) also 

 used 1 : 2 acetic acid on account of its inactivity towards ferrous car- 

 bonate. Extraction with hot dilute hydrochloric acid has been employed, 

 and Heinrich (11) gives the following scale of minimum contents of lime 

 (CaO) extractable with 10 per cent. acid. According to this a lime 

 content of 



0-05 % is sufficient for the growth of potatoes and rye, 

 005-0-10 is suflioiont for the growMi of oats and barley, 

 010 is sufficient for the growth of peas and vetches, 

 0-12 is sufficient for the growth of clover and 

 0'20-O'30 is sufficient for the growth of lucerne. 



Maercker (12) gives two scales — one for sandy soils and another for 

 loams — 10% hydrochloric acid being used, while Orth (13) gives still 

 another for data obtained by the use of strong acid. It soon became 

 evident that the lime thus removed from the soil could not fairly repre- 

 sent the amovmts of lime available either for plant growth or for the 

 correction of soil acidity, and other methods depending on the inter- 

 action of lime compounds in the soil with various neutral salts were 

 suggested. 



The one proposed by Stiitzer and Uartleb (Jl) icst.s ujjou the de- 

 composition of soil carbonates by the addition of ammonium chloride, 

 the ammonium carbonate formed being then estimated by distillation. 



Following a method indicated by Kellner (15) for the determination 

 of the absorptive power of soils, Meyer (16) elaborated one for the 

 estimation of lime in an available state. This consists in the treatment 

 of 10 grms. of soil with 100 c.c. of a 10 per cent, solution of ammonium 

 chloride for three hours and the determination of the lime removed in 

 the solution. Gregoire showed, hovrever, that tJiis period was not 

 sufficient for the removal of the whole of the available lime and recom- 

 mends extension of the period to 10 hours. In view of the fact that 

 this method often gives anomalous results, Weibull (17) drew into con- 

 sideration another factor — that of the organic matter of the soil as 

 indicated by "loss on ignition." On the assumption that the lime 



