210 § 110. ANALYSIS OF SOILS AND EOCKS. 



1. In this burned limestone, determine the alkalies 

 soluble in water by treating 150 grms. with 1500 c.c. of 

 distilled water, with frequent agitation during a digestion 

 of 24 hours. Then pour off 1000 c.c. of the supernatant 

 liquid, as clear as possible, filter, if the liquid is not per- 

 fectly clear, remove silica as usual (§ 58, «), by evapora- 

 tion to dryness and treatment with hydrochloric acid, 

 and eliminate the alkalies as chlorides (§ 93, G). 



2. Digest another portion of 100 to 150 grms. of the 

 burnt lime, according to its richness in silicates, 48 hours 

 in tlie cold, with tliree times its weight of concentrated 

 hydrocliloric acid, filter the mixture, and wash the resi- 

 due, first with cold, and then with hot water. Determine 

 phosphoric acid and the alkalies in this solution (Scheme 

 I., § 94) ; no ferric chloride need be added. 



It sometimes happens that a considerable separation of 

 gelatinous silica renders the filtration of the hydrochloric 

 acid solution very difiicult. In this case, evaporate the 

 whole mixture to complete dryness, moisten the residue 

 with concentrated acid, let it stand awhile, boil with di- 

 lute acid, filter, and examine this filtrate for phosphoric 

 acid and alkalies, as above. The solution will contain all 

 that would ordinarily be dissolved by both cold and hot 

 hydrochloric acid. 



Treat the residue, insoluble in cold hydrochloric acid, 

 with hot acid, if not already so treated, and then with 

 sulphuric and hydrofluoric acids (§ § 101, 102, and 103). 



('. To determine whether a limestone will yield good 

 mortar lime, digest 4-5 grms. with dilute hydrocliloric 

 acid, evaporate the whole to dryness, after adding a few 

 drops of nitric acid, boil the residue with acidified water, 

 filter, wash, ignite, and weigh. A good limestone, for 

 this purpose, should not leave more than 5 to 10° |„ of in- 

 soluble matter. 



The solution may be examined for alumina, ferric oxide, 



