310 Mr. Schweitzer on an Analysis of the 



cautions for carbonate of lime, when it weighed 40*579 grs. ; 

 it was again dissolved in nitric acid, when 0*005 gr. silica (/) 

 was left. The solution of nitrate of lime gave no indications 

 of manganese nor of strontia when the nitrate was changed 

 into a chloride. [If earthy carbonates be dissolved in nitric 

 acid, and tested for strontia by sulphate of lime, small quan- 

 tities are not detected, but when the carbonates are changed 

 into chlorides minute proportions are easily evidenced by that 

 test.] Deducting 0*005 from 40*579, there remains 40*574 

 grs. of carbonate of lime {m). The filtered fluid derived from (I) 

 was now examined for magnesia. The simplest method would 

 be to evaporate the fluid to dryness, and to ignite the residue 

 until the ammoniacal salts are dissipated ; however, this offers 

 some difficulties, particularly as the mass on approaching the 

 dry state rises and involves the probabilities of loss. It is 

 therefore an advisable method to halve the fluid, and ascertain 

 the quantity of magnesia in the one part by phosphate of am- 

 monia, and in the other by evaporation, by which latter pro- 

 cess also a few other ingredients, in very small quantity, which 

 have hitherto escaped, may be found. One portion yielded, 

 when precipitated by phosphate of ammonia, &c., 10*344 grs. 

 phosphate of magnesia, equivalent to 3*793 of magnesia. 

 The other half was evaporated to dryness and the residue ig- 

 nited, when it left 4* 186 grs. of a perfectly white magnesia. 

 This was boiled with water, which left after evaporation 

 0*370 gr. of carbonate of soda (w), equivalent upon the 

 whole mass to 0*740 gr. When re-dissolved it acted strongly 

 upon turmeric paper, effervesced with acids, and gave a 

 very minute crystalline precipitate with perchloride of pla- 

 tinum, indicating that the soda contained a slight admixture 

 of potassa. The soda was derived from a soda-carbonate of 

 magnesia, which became decomposed by ignition, and from 

 which boiling water extracted the soda*. The residue from 

 which the carbonate of soda was separated was dissolved in 

 hydrochloric acid, when again a small proportion of 0*010 gr. 

 silica was left, making the whole silica 0*020 {o). If the 

 amount of silica (0*010) and that of soda (0*370) is deducted 

 from 4*186, there remains 3*806 grs. of pure magnesia, 

 which upon the whole gives magnesia 7*612 grs. {p), equi- 

 valent to 15*759 carbonate of magnesia; this amount corre- 

 sponds very closely with that obtained by the first experi- 

 ment. The amount therefore of earthy ingredients obtained 

 by analysis stands thus : — 



* By performing the latter method of ascertaining magnesia, it is indis- 

 pensably necessary to examine the oxalate of ammonia, which frequently 

 yields after ignition traces of alkaline carbonates. 



