268 NEUTRAL ALKALINE PHOSPHATES. 



expected not being present. It was known that this circum- 

 stance could not arise from a want of decomposition of the 

 original matter, as it was kept fused for half an hour with 

 four times its weight of carbonate of soda; therefore the only 

 rational conclusion was that the phosphate of lime was in 

 the first case decomposed by the soda, but was subsequently 

 reformed upon treating the fused mass with water. This has 

 been verified by direct experiment. 



Twelve grains of neutral phosphate of soda and six of car- 

 bonate of lime were digested for two hours in four ounces 

 of water at 180° Fah., when the carbonate of lime was found 

 almost completely decomposed, and the clear solution upon 

 evaporation furnished carbonate of soda. 



Six grains of precipitated carbonate of lime added to a 

 solution of twenty grains of phosphate of soda (equivalent 

 proportions of each), in one ounce of water, were kept in a 

 vial for one month, the temperature never exceeding 65° Fah. 

 At the expiration of this time the insoluble portion contained 

 three and a half grains of phosphate of lime, corresponding to 

 a decomposition of about two and a half grains of the carbonate 

 of lime. The soluble portion indicated a corresponding portion 

 of carbonate of soda. 



Other insoluble carbonates were experimented with, as the 

 carbonates of magnesia, strontia, baryta, and lead. The re- 

 sults were the same, differing only in degree. Even hydrated 

 alumina decomposes slightly the phosphate of soda when boiled 

 with it for a length of time. 



I tried two other neutral salts, the acids of which produce 

 insoluble salts with lime, to see if they would act in the same 

 way. The chromate and the tartrate of potash were digested 

 a length of time upon the carbonate of lime, but no decompo- 

 sition ensued. 



I shall not attempt to seek for an explanation of this at 

 present, but shall go on collecting facts of a similar character, 

 to endeavor to find out some general principle that may operate 

 in this and in other cases. This fact itself would not be pub- 

 lished at the present time if it were not of the greatest impor- 

 tance to put analytical chemists upon their guard ; for but a 

 few days ago an individual wrote to me that he was estimating 

 the phosphate of lime in a certain class of bodies by fusing 



