238 § 121. FEKTILTZEES. 



tate the sulphuric acid in the filtrate with baric chloride ; 

 transfer the filter with its contents to a deep beaker, and 

 dissolve the carbonate in dilute hydrochloric acid with 

 the usual precautions, filter, wash well, dry, ignite, and 

 weigh the residue of sand and clay. Determine lime and 

 magnesia in the filtrate in the usual manner (§ 50, h). 



e. Alkalies. — To determine these in gypsum, boil 10 

 grms. repeatedly with dilute hydrochloric acid, filter, and 

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



f. A determination of carhonie acid will furnish means 

 of estimating the amount of calcic carbonate in the gyp- 

 sum ; take 5-10 grms. for the analysis (§ 60). 



SALT. POTASH COMPOUNDS. 



121. A. Salt. a. Water.— Gently ignite 3-4 grms,, 

 well pulverized, in a platinum crucible that is kept well 

 covered, and carry the temperature finally to a dull red. 



b. Complete analysis. — Dissolve 10 grms. in hot water, 

 filter the solution into a litre flask, and wash, dry, ignite, 

 and weigh the insoluble residue. 



This residue consists mostly of sand and clay. If gyp- 

 sum is contained in it, digest it Avith dilute hydrochloric 

 acid as long as anything appears to be dissolved, filter 

 the solution, add ammonia in excess to the filtrate, filter 

 out the precipitated ferric oxide and alumina, precipitate 

 lime in the filtrate by ammonic oxalate, and sulphuric acid 

 in the filtrate from the calcic oxalate by baric chloride 

 after acidification with hydrochloric acid. 



Bring the volume of the aqueous solution of the salt, ob- 

 tained above, to 1000 c.c, and determine lime and mag- 

 nesia in 400 c.c. (§ 50, />), and chlorine in another portion 

 by the volumetric process (§ 03, b). Dilute 300 c.c. with 

 more water, acidify it with hydrochloric acid, and exam- 

 ine the solution for sulphuric acid and the alkalies (§ 93, 



