rilOSPHORIC OXIDE IX FEltTILISERS. 



2G9 



In most of the mixed or complete fertilisers that have 

 been recently placed on the South African market, material 

 that was obtainable locally has had to be substituted in place 

 of readily available forms of constituents. Especially was 

 this the' case as reg-ards potash, as neither the sulphate,, 

 chloride nor nitrate has been available in quantity, and resort 

 has been made to the large amount of available ash in the 

 country. I refer more especially to the TJnion. It is a 

 well-known fact that any material of a basic nature, such as 

 calcium oxide, hydrate, or carbonate or ashes, should not be 

 mixed on any accounti with water-soluble phosphoric oxide, 

 owing- to chemical action taking- place, with a loss of water- 

 soluble phosphoric oxide to that of water-insoluble forms. 

 However, in view of the scarcity of suitable material, as 

 pieviously mentioned, this has actually been canied out, and 

 many of the mixed fertiliseis, with few exceptions, have 

 ashes either derived from kraal manure, seaweed or jdant for 

 supplying' the necessary amount of potash. 



To test how far the solubility is affected by other than 

 those mentioned in the paper referred to above, the following- 

 mixtures were prei>ared : (a) Superphosphate and Ephos basic 

 phosphate: (b) superphosphate and Saldanha Bay phosphate; 

 (c) supeiiohosphate and g-round limestone; (d) superphosphate 

 and kraal manure ash; (e) superphosphate and seaweed ash; 

 (f) superphosphate and bush or plant ash. 



The preparations of the above mixtures and analyses 

 thereof Avere made on identical lines with those in my previous 

 article. 



The composition of the various materials used in this set 

 of experiments was as follows : — 



The following- percentages of water-soluble phosphoric 

 oxide Avere found in dift'erent mixtures : — 



