676 



Journal :>t Agriculture , \ictoria. [11 Nov., 1912. 



THE RELATIVE SOLUBILITY OF THE PHOSPHORIC 

 ACID IX ROCK PHOSPHATE AND BONE-DUST, 



TV. C. Robertson, Chief Deputy Chemist. 



The following table gives the results from an experiment recently con- 

 ducted at the Agricultural Laboratory. 



The object of the test was to ascertain the availability of the phosphoric 

 acid in rock phosphate and bone-dust respectively. 



A preliminary experiment was carried out by placing two perforated tin 

 vessels containing pulverised rock phosphate and bone-dust respectively, in 

 a garden soil and covering them to a depth of 12 inches. 



The soil was watered every morning and, by a launder arrangement, 

 the drainings were separately collected in two glass vessels. 



After the expiration of one month, the drainage water in each vessel 

 was tested for phosphoric acid, with the result that the drainings from the 

 bone-dust gave a distinct affirmative reaction, whereas the test on the liquid 

 from the rock phosphate gave an entirely negative result. 



In the experiment under review, the mode of procedure was as 

 follows : — 



Two lots of virgin soil, each weighing 7 lbs., were placed in two 

 earthenware jars having an outlet at the bottom. 



From the latter, a tube with stop cock attached, led to a glass jar con- 

 taining in one case 100 grammes of finely ground rock phosphate, and in 

 the other the same amount of bone-dust. 



The following diagram will serve to show the arrangement of the 

 apparatus: — ■ 



or ' 

 'fi,one dust- 



The sod in the earthenware receptacles was kept saturated with water 

 and the dramage conducted through the outlet tube to the glass jars and 

 thus allowed to act upon the material contained therein. The experiment 

 was conducted over a period of four months, but progress analyses were 

 conducted at the end of {a) one week, {b) one month, {c) four months. 



The soil in the first instance was analysed for humus and available 

 phosphoric acid and was found to contain 2.3 per cent, humus, whilst the 

 available phosphoric acid content was infinitesimal. The soil water was 

 of an acidity equal to .012 per cent, citric acid. 



