228-235] WET EXAMINATION FOR METALS 67 



ignition-tube ; evolution of ammonia indicates presence of 

 organic nitrogen. 



WET EXAMINATION FOR METALS 



228. If the substance be a solid it is first of all necessary 

 to bring it into solution. 



Finely powder the substance in a mortar. If the sub- 

 stance is very hard an agate mortar must be used. 



229. Process of Solution.— Boil up as much of the 

 powdered solid with distilled water as will cover a shilling. 

 If the substance dissolves proceed with the analysis. If 

 some remains undissolved heat another portion of the solid 

 with dilute hydrochloric acid for several minutes. If all 

 dissolves proceed with the analysis. If all does not dis- 

 solve heat a fresh portion with strong hydrochloric acid to 

 which has been added a little strong HN0 3 ; dilute, filter 

 if necessary, and proceed with the analysis. If any residue 

 is left it will require treating as an insoluble substance by 



paragraph 250. 



NOTES TO TABLE II. 



230. — If the temperature of ignition be too high, insoluble A1 2 0, 

 and Fe 2 3 will be formed which will not redissolve when treated with 

 HC1. If organic matter is present the dish should be gently heated 

 with a small flame until the black carbonaceous matter is burnt away. 



231. — If AmCl is added in insufficient quantity Mn and Mg may 

 be precipitated with AmHO. If AmCl is added in very large quantity 

 MnS is prevented from precipitating when Am 2 S is added. 



232. — Since traces of Mn may be precipitated with AmHO, it is 

 as well to test a portion of this residue for Mn by fusion on platinum 

 foil with Na 2 C0 3 and KN0 3 , when a green mass will be formed. 



233. — Since HNO s has been added in an earlier part of the 

 analysis, the iron at this stage will be in the ferric state. A small 

 quantity of the original substance dissolved in HC1 should be tested 

 for ferrous and ferric iron by paragraphs 165 and 171. 



234. — Commercial KHO and NaHO frequently contain AL These 

 reagents should be tested by acidulating and adding AmHO. 



235. — Potassium may also be detected at this stage by adding a 

 small quantity of strong platinum chloride or sodium picrate solution 

 and stirring with a glass rod ; a yellow crystalline precipitate will be 

 formed in both cases if K is present (188, 188a). 



F 2 



