.Tatixdka Natii Skx 



35 



niaiijiaiiate required to oxidise these. The percolates from jars Nos. 1, 

 5 and 9 (all containing per cent, potsherds) required, per litre, 0-096, 

 0-094 and 0-069 gram, respectively of oxygen as compared with 0-014 

 gram, required in the case of the percolate from jar No. 7 (containing 

 twenty per cent, potsherds) i. 



A fortnight later the jars were again irrigated, this time with distilled 

 water. Analyses of the resulting percolates are recorded below. 



* The distilled water contained 0-64 parts dissolved oxygen per million. 



The result of the analysis showed a marked difference in the nature of 

 the percolates from jars containing no potsherds as compared with those 

 from jars containing added potsherds. The percolates from jars without 

 any potsherds in them were coloured and contained less dissolved oxygen 

 than the percolates from the other jars; the difference in the oxygen 

 content was, however, not so marked as in the first set of percolates. 

 At this stage of the experiment artificial irrigation was discontinued and 

 the jars were exposed to the rain and the resulting percolates were ex- 

 amined. Later on the jars were once more irrigated with distilled water 

 in December. 



As the monsoon proceeded, the earth-filling round the jars often gave 

 way dislocating and occasionally breaking the tubes through which the 



1 Nitrates were determined colorimetrically by the phenol disulphonic acid method 

 The dissolved o.xygen and the oxygen required were estimated by Rideal's and by 

 Forschammer's processes respectively. 



3—2 



