162 ON PRECIPITATED CARBONATE OP LIME. 
1. Density of the solutions which are used in the pre- 
cipitation, produces the least effect of the three circum- 
stances noticed; but it may be stated, that very strong pro- 
duce a finer precipitate than very weak solutions — probably 
in consequence of the density causing a more rapid forma- 
tion of the carbonate — and hence, less time is afforded for 
the concretion of the particles in crystallizing. 
2. The nature of the compounds used to effect precipi- 
tation produces more manifest effects. With respect to the 
lime compound, the variation is not very great. Acetate 
of lime, however, produces a precipitate more divided than 
chloride of calcium. With respect to the precipitant the choice 
is more important. Carbonate of potassa is totally unfit to 
procure a good pharmaceutical preparation. It produces a 
precipitate which is coarse and gritty, being constituted of 
crystalline grains of such magnitude, that the carbonate 
thus made presents the appearance of fine sand ; when dry, 
the particles cohering very slightly either to each other, or 
the containing vessel, so as readily to roll over, on every 
change of position. The crystalline structure is here manifest 
through a magnifier of no great power. 
Carbonate of soda and carbonate of ammonia, afford a 
better preparation ; the precipitate being more divided, but 
still possessing some of the above noticed sabulous cha- 
racters — not, however, so very manifest as in the preceding 
case. The size of the particles may still be detected by the 
tongue, which affords the most sensitive surface for the per- 
ception of grit. 
3. The temperature at which the precipitate forms, is 
very material to the resulting fineness of the precipitated 
carbonate. The preceding remarks apply to common tem- 
peratures, the precipitate increasing in minuteness of di- 
vision with the rise of temperature, and when boiling so- 
lutions are used, loses entirely the sandy character. The 
precipitate then formed is smooth, and perfectly without 
roughness, even when placed on the tongue, and the particles 
