48 'Calcaretlis Earth. [Book VI. 



earth are fufFicient to faturate*a large quantity of 

 water. There are two other circumftances not in- 

 cluded in the definition, which make part of the idea 

 of an earthy fubftahce ; ift, a great degree of fixed- 

 nefs j 2dly, a difpolition to form a glairy concretion 

 when melted with certain other fubftances. 



Lime, properly fo called, is obtained by expelling 

 the carbonic acid from, calcareous fubftances by means 

 of heat. 'Calcareous earth is in a tolerably pure ftate 

 in common quick-lime ; but if it is required perfectly 

 free from foreign admixture, it may be obtained by 

 the following procefs : If pounded chalk is feveral 

 times boiled in diftilled water, the remainder will con- 

 fift almoft entirely of calcareous earth, combined with 

 the carbonic acid. If diftilled vinegar is added to the 

 powder thus obtained, it will form a faline combina- 

 tion with the lime only, to the exclufion of all extra- 

 neous matter. To a folution of this, decanted from 

 the impurities, mild volatile alkali being added, the 

 alkali will unite with the vinegar, while the calcareous 

 earth feizes the carbonic acid of the alkali, and falls 

 to the bottom in the ftate of a perfectly pure chalk. 

 The carbonic acid may be driven off by heat^ and 

 calcareous earth is thus obtained in its rrioft fimple 

 ftate. 



The relative weight of quick-lime to that of flaked 

 lime is as j,ooo to 1,287. Every pound can im- 

 bibe four ounces four drams and fifty- three grains of 

 water. 



Calcareous earth is foluble in the nitrous and mu- 

 riatic acids, and forms deliquefcent falts. It is pre- 

 cipitated from its folutions by means of vitriolic acid, 

 with which it forms a nearly inlbluble compound, 

 called felenite, (or plaifter of Paris.) Pure Calcareous 



* See note *, p. i. 



earth, 



