576 



Transactions. 



Series III. — Experiments made to ascertain, if possible, the effect of 

 varying the amount of phosphate taken and the time of stirring showed 

 that the solubility is increased both by increasing the amount taken and 

 the time of shaking. Hereafter, therefore, weighed quantities of the phos- 

 phate were taken, the contents of the tube were shaken for five hours, 

 then allowed to stand until run off for estimation. 



Series IV. — 0-25 gram was taken, giving results as shown in fig. 3. The 

 two higher results were obtained by shaking for ten hours. 



Series V. — 1 gram taken. Both curves IV and V, though widely sepa- 

 rated, show marked regularity, as far as they were taken. 



Series VI. — 0-5 gram taken. Here (see series VI, fig. 3) a very large 

 drop was observable between 25 and 30 atmospheres, for which there was 

 no accounting. 



s 



•} 



O -If 



in 



if. is 



Pressure. 



f\t moij J)tr?5 



Fig. 3. 



An attempt to confirm this peculiarity was made in Series VII, but 

 the enamel began to flake in the second run. Later it flaked during the 

 first run after re-enamelling, and on evaporating the solution the solid 

 residue had a pale blue-green tint in the mass, and gave a slight blue colora- 

 tion with ammonia. The slight surface action on the copper probably had 

 some effect upon the solubility, which is here very irregular. After trying 

 varnish in the tube without success, it was plated, as continuously as its 

 structure would permit, with standard gold. 



Series VIII was undertaken to verify, if possible, the peculiar results 

 of series VI. The results, at pressures from 42 down to 4-4 atmospheres, 



