Wright. — The Determination of Milk-fa/. 573 



The method of Gottlieb as described by Thorpe* was used in the above 

 determinations, and is as follows : 10 c.c. of milk are measured into a tall, 

 narrow cylinder, graduated in 0-5 c.c, and holding 100 c.c. ; 1 c.c. of 

 ammonia (sp. gr. 0-96) is added, and then 10 c.c. of alcohol. The mixture 

 is well shaken ; 25 c.c. of ether, which need not be dry, are added ; and 

 the contents of the tube well mixed. Finally, 25 c.c. of light petroleum 

 are added, and the mixture again well shaken. It is essential that the con- 

 tents of the tube be mixed after the addition of each reagent, or the results 

 may be very low. The cylinder is then left for six hours, the volume of 

 the ethereal solution measured, and 50 c.c. removed, evaporated, and the 

 fat dried and weighed. 



The question naturally arises as to whether or not the increased result 

 is due to some substances other than fat, introduced by the reagents used 

 in the Gottlieb method, or through their action. A blank test of the 

 chemicals used was made and the small amount of residue obtained on 

 evaporation deducted from the results. 



Olsenf has shown that the results obtained by the Gottlieb method 

 are the true fat-content of dairy-produce, and this is of special importance 

 in the case of milk or other dairy-products containing only small amounts 

 of fat. 



Art. LII. — On the Influence of Pressure on the Solubility of Tricalcic Phos- 

 phate in Carbonic-acid Solutions. 



By P. S. Nelson, M.Sc 



Communicated by Dr. Evans. 



[Bead before the Canterbury Philosophical Institute, 1st July, 1914.] 



Robert Wadington, in 1871 (Journ. Chem. Soc, p. 80), treated samples 

 of bone-ash repeatedly with a solution of carbon dioxide in water, and found 

 a solubility of tricalcic phosphate of 0-147 gram per litre. T. Schloesing 

 (Comp. Rend., 1900, vol. 131, pp. 149-53) determined the solubility of freshly 

 precipitated tricalcic phosphate in pure water, in carbon-dioxide solutions 

 of various strengths, and in similar solutions containing calcium bicarbonate. 

 He found in 1 litre of — 



Water saturated m , , 1TT , , n Calcium- 



with ^ater i W ** eT & Rl , re bicarbonate 



carbon dioxide saturated saturated water go , ution 



91-9 48-5 6-9 1 1 



milligrams of phosphoric acid, as P 2 5 . This result seemed to suggest 

 that the solubility of the tricalcic phosphate depended, to some extent at 

 least, on the amount of carbon dioxide in solution. 



As no record dealing with the question could be found in the Journal 

 of the Chemical Society, nor in the Journal of the Society of Chemical 

 Industry, it was determined to ascertain the effect of carbon dioxide at 

 higher pressures than atmospheric upon the solubility of the phosphate. 



* Diet. Applied Chem., rev. ed., vol. 3, pp. 531, 532. 

 f Bulletin No. 105, U.S. Dept. Agric, p. 109. 



