A. A. Ramsay 



289 



a 2 % citric acid solution. The results are given in tabular form and 

 are practically self-explanatory. 



It will be noted that 90-5 % of the Ume and 91 % of the phosphoric 

 acid have gone into solution in the first extraction of 30 minutes, and 

 that the lime and phosphoric acid extracted are very nearly in the ratio 

 of SCaOrPaOj. 



In the second extraction it will be seen that there is rather less lime 

 found than would be necessary to produce CagPgOg with the phosphoric 

 acid found. This would appear to indicate that the lime and phos- 

 phoric acid had gone into solution as a mixture of di- and tricalcium 

 phosphate. 



In the third extraction, the lime found is greater than that which 

 would be necessary to form CagPgOg with the P2O5 found, so that part 

 of the lime found must have gone into solution as calcium citrate. 

 This also appears to have taken place in the fourth extraction. 



After four extractions the whole of the lime and the whole of the 

 phosphoric acid have gone into solution. 



It should also be noted that under existing methods of analysis 

 this compound (tricalcic phosphate) would be stated to contain 38-34 % 

 "citrate soluble" phosphoric acid out of a total of 42-36%. 



Experiment (6). Extraction of 5 grams of an intimate mixture 

 consisting of 75 % pure tricalcic phosphate and 25 % pure calcium 

 carbonate with 500 c.c. of 2 % citric acid solution. 



3-75 grams tricalcic phosphate containing 50-12 % CaO, 

 42-36 % PoOs will contain 



1-25 grams calcium carbonate containing 56-00 % CaO, 

 will contain 



2-5795 



1-5885 



