98 Dr. J. L. Smith on Neutral Alkaline Phosphates. 



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 sub- 

 sequently 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 carbon- 

 ate of lime, were digested for two hours in four ounces of water 

 at 180° Fahr., 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 por- 

 tion indicated a corresponding portion of carbonate of soda. 



Other insoluble carbonates were experimented with, as the car- 

 bonates of magnesia, strontia, baryta and lead ; the results were 

 the same, differing only in degree. Even hydrated alumina de- 

 composes 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 in- 

 soluble 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 decomposition 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 This fact itself would not be published at the pres- 

 ent time, if it were not of the greatest importance, to put analyt- 

 ical chemists upon their guard ; for but a few days ago an indi- 

 vidual wrote me that he was estimating the phosphate of lime in 

 a certain class of bodies by fusing them with carbonate of soda, 

 which will certainly be productive of some error ; and although 

 it is to be regretted that our methods of arriving at phosphoric 

 acid in analysis may be diminished by this fact, still it will only 

 stimulate us to find out some other to solve this, one of the most 

 difficult and annoying problems in analytical chemistry. 



Charleston, S. C, Oct. 29, ]844. 



