II. I*). lIlTTOHINSOX AM) K, MacLeNNAN S1» 



appreciablf ((uantities of aninionia when heated with barium hydroxide 

 solution at 100° and the amount thus formed must be taken into con- 

 sideration. 



A method which has, perhaps, been more extensively used in the 

 United States than any other is that introduced by Veitch (35). In 

 this, three lots of soil each of 10 grms. are weighed into platinum basins 

 and about 50 c.c. of water added; three different volumes, say 10, 20, 

 and 30 c.c. of standard calcium hydroxide solution are added and the 

 basins are placed immediately on a water bath and their coiitents 

 evaporated to dryness. With the aid of 100 c.c. of distilled water the 

 soils are then transferred to Jena glass flasks and allowed to stand 

 overnight: the reaction of about 50 c.c. of the filtered liquid is tested 

 by boiling with phenolphthalein, the volume being reduced by boiling, 

 if necessary, to 5 c.c. The three quantities of lime-water taken will 

 generally suffice for orientation — one of the (juantities being too small 

 and the others too large for exact neutralisation or rice versa. Within 

 the limits thus set by the trial determination, other tests are made where 

 the amounts of lime-water vary by no more than "2 c.c. ; the approximate 

 requirement may thus be obtained. 



The method is based on the fact that the slight excess of lime-water 

 present after the neutrahsation of the acid soil material is conveited 

 into carbonates or bicarbonates, the boiling solution of which gives an 

 alkaline reaction with phenolphthalein. The strict adherence to the 

 prescribed directions in these methods is essential — the adoption of an 

 extended period of digestion as, for instance, in the Albert method, or 

 failure to place the soils at once on the steam bath as in Veitch's method 

 would probably lead to ini trustworthy results. 



Wheeler and his colleagues and also Veitch attempted to obtain a 

 measure of soil acidity by digestion of the soil with lime-water in the 

 cold. The results thus obtained by Veitch were higher than those 

 given by his acidity method, and there appears to be no reason to 

 doubt that the introduction of the heat factor is responsible for this 

 difference. 



Gregoire, Hendrick, Carpiaux and Germain (36) have recently in- 

 vestigated the action of soils on a " Kjeldahl's solution " of the following 

 composition : 



55-3 grnis. potassium iodide, 



14-3 ,, potassium iodate, 



99-2 ,, sodium thiosulphate (cryst.) and 



1000 c.c. water. 



