354 SOIL CONDITIONS AND PLANT GROWTH 



(i) Ten grnis. of the air-dry earth, which has passed a 3 mm. 

 sieve, are weighed out into a porcelain basin and triturated with 

 100 c.c. of N/5 hydrochloric acid, further acid being added if much 

 calcium carbonate is present. After standing in contact with the 

 acid for one hour, the mixture is transferred to a dried, tared filter 

 which is washed until acid-free, dried and weighed. The loss repre- 

 sents hygroscopic moisture and material dissolved by the acid. 



(2) The soil is washed off the filter with ammoniacal water on 

 to a small sieve of 100 meshes to the linear inch, the portion passing 

 through being collected in a beaker marked at 10, 8 "5, and 7*5 cm. 

 respectively from the bottom. The portion which remains upon the 

 sieve is dried, weighed, and divided into "fine gravel" and "coarse 

 sand " by means of a sieve with round holes of i mm. diameter. 

 The portion which does not pass this sieve is the " fine gravel ". 

 This is dried and weighed. The difference gives the "coarse sand ". 

 If required, both these fractions can also be weighed after ignition. 



(3) The portion which passed the 100 mesh sieve is triturated 

 with a rubber pestle (made by inserting a glass rod as handle into an 

 inverted rubber stopper), and the beaker filled up to the 8*5 cm. 

 mark and allowed to stand for twenty-four hours. The ammoniacal 

 liquid which contains the "clay" is then decanted off into a Win- 

 chester quart bottle, the operation being repeated as long as any 

 matter remains in suspension for twenty-four hours. The liquid 

 containing the "clay " is either evaporated in bulk or measured, and, 

 after being well shaken, an aliquot portion taken and evaporated. 

 In either case the dried residue consists of "clay" and "soluble 

 humus ". After ignition the residue gives the " clay," and the loss 

 on ignition the "soluble humus". Here minimum value of 

 V = o '0000 1 cm. per second, and the minimum diameter of the 

 particles = '0013 mm. 



(4) The sediment from which the " clay " has been removed is 

 triturated as before in the beaker, which is filled to the 10 cm. mark 

 and allowed to stand for 100 seconds. The operation is repeated 

 until the "fine sand" settled in 100 seconds is clean, when it is 

 collected, dried, and weighed. 



Here minimum value of & == ci cm. per second ; the calculated 

 minimum diameter = "037 mm. 



(5) The turbid liquid decanted from the " fine sand " is collected 

 in a suitable bottle, allowed to settle, and the clear liquid syphoned 

 or decanted off. The sediment is then washed into the marked 



