MAGNESIUM AND BERYLLIUM. 63 



this regard. When 1 per mille solutions of beryllium sulphate and 

 dipotassium phosphate are mixed the liquid is at first clear at the 

 ordinary temperature, but gradually becomes opalescent, and after one 

 day the beryllium is precipitated as a iiocculent phosphate, but if the 

 mixture is heated or if some sodium acetate is added a flocculent 

 precipitate is produced at once. Magnesium sulphate behaves very 

 differently, giving no precipitate whatever under the same conditions. 



If a 10 per cent solution of monopotassium phosphate is mixed with 

 a 10 per cent solution of magnesium sulphate no precipitate is formed 

 at the ordinary temperature, and the liquid remains clear even on boil- 

 ing. This, however, is not the case with beryllium sulphate, which 

 produces a copious iiocculent precipitate in a few minutes, and even if 

 more dilute solutions, as, for example, a 1 per cent solution of mono- 

 potassium phosphate and beryllium sulphate, are mixed, the mixture 

 becomes turbid on boiling. 



Although a higher diluted solution of beryllium sulphate gives no 

 precipitate with monopotassium phosphate, the addition of sodium 

 acetate, even at the ordinary temperature, will cause a precipitate of 

 beryllium phosphate. Thus even in a dilution of 0.001 per cent beryl- 

 lium sulphate turbidity will be produced, and finally some flocculi 

 will be deposited. Under the same condition solutions of magnesium 

 sulphate, whether highly or moderate^ diluted, will remain perfectly 

 clear. 



It is seen, therefore, that there is a fundamental difference between 

 beryllium and magnesium salts in their behavior to phosphoric acid — a 

 difference which amply accounts for the fact that beiyllium salts can 

 not replace magnesium salts as far as the process of the assimilation 

 of phosphoric acid is concerned. In this respect magnesium is unri- 

 valed even by the most closely related elements. With the properties 

 of easy dissociation of the salts and its character as only a weak base, 

 magnesia unites a moderate solubility of the secondary phosphate not 

 found with any other related base. Although beryllium oxid is also a 

 weak base, the fact that it is much more inclined than magnesia to 

 yield an insoluble phosphate renders it unsuitable for the function 

 mentioned. . 



As to the rarer elements it may still be questioned whether there may 

 not exist among them some that could physiologically replace magne- 

 sium or calcium. The experiments with cerium and lanthanum showed 

 no evidence in favor of that view, these salts killing algre in a solution 

 of 0.1 per cent. Thorium sulphate is not so injurious, but no further 

 studies as to whether it can be utilized for any physiological function 

 have been made, nor have any experiments been made with yttrium, 

 niobium, or some other rare elements. 



