64 Dr Davy on Carbonate Acid 



dition of ammonia. I may mention in this place, in farther 

 illustration of the solvent pov^fer of carbonic acid over phos- 

 phate of lime, an experiment that is rather paradoxical. 

 If to a solution of phosphate of lime in distilled vinegar 

 carbonate of lime in fine povv^der be added, there is an instant 

 and strong effervescence, and phosphate of lime is found to 

 be precipitated ; but if calc-spar, in small pieces, be substi- 

 tuted for the powder, comparatively little gas is given off, 

 and very slowly ; the solution, in brief, becomes saturated with 

 carbonic acid, and though an acetate of lime is formed, no 

 phosphate of lime is thrown down, it being kept in solution 

 by the carbonic acid, as is proved by heating the solution, 

 when, on the expulsion of the gas, the phosphate of lime is 

 precipitated. 



Gypsum. — Some of this compound in powder, not of absolute 

 purity, from a parcel imported for use as a manure, was sub- 

 jected to the action of carbonic acid in water for twelve days. 

 The results of the trial were negative. On the addition of 

 ammonia to the filtered water, there was no precipitation of 

 sulphate of lime ; nor, on exposm-e to the atmosphere of an- 

 other portion of the water, was there any film or pellicle of 

 the sulphate observable on the surface, after the greater part 

 of the gas had escaped, or any deposition on the inside of 

 the glass vessel ; thus indicating that water impregnated 

 with carbonic acid gas had not its power of dissolving gyp- 

 sum increased thereb}'. And a few experiments which I 

 have made with other acids on this compound, as the sul- 

 phuric, muriatic, and acetic acids diluted, have given a like 

 I'esult, viz., that these acids are not solvents of sulphate of 

 lime. 



Alumine. — The portion of this earth, subjected to the ac- 

 tion of the cai-bonic acid water, had been obtained from a 

 solution of alum by the addition of ammonia, and conse- 

 quently retained a minute proportion of sulphuric acid, even 

 after having been well washed. On examination, after seven 

 days, the results were entirely negative ; ammonia, added to 

 the water the instant it had been filtered, did not occasion 

 the slightest turbidness ; no pellicle appeared on another 

 portion as the gas escaped on the exposure to the air ; nor 



