214 METALS AND THEIR COMBINATIONS. 



it ought to be treated as follows : The substance, if not liquid, is cut into pieces, 

 well mashed and mixed with water ; the liquid or semi-liquid substance is 

 heated in a porcelain dish over a steam bath with hydrochloric acid and potas- 

 sium chlorate until the mass has a uniform light yellow color and has no longer 

 an odor of chlorine. By this operation all poisonous metals (lead and silver 

 excepted, because insoluble silver chloride and possibly insoluble lead sulphate 

 are formed) are rendered soluble even when present as sulphides, and may 

 now be separated by nitration from some remaining solid matter. The clear 

 solution is heated and treated with hydrosulphuric acid gas for several hours, 

 when arsenic and all metals of the arsenic and lead groups are precipitated as 

 sulphides, a little organic matter also being precipitated generally. 



The precipitate is collected upon a small filter and treated with warm ammo- 

 nium sulphide, which dissolves the sulphides of arsenic and antimony, leaving 

 behind the sulphides of the lead group, which may be dissolved in nitric, or, if 

 mercury be present, in nitro-hydrochloric acid, and the solution tested by the 

 methods mentioned for the respective metals. The ammonium sulphide solu- 

 tion is evaporated to dryness, this residue mixed with nitrate and carbonate of 

 sodium, and the mixture fused in a small porcelain crucible. By the oxidizing 

 action of the nitrate, both sulphides are converted into the higher oxides, 

 arsenic forming sodium arsenate, antimony forming antimonic oxide. By 

 treating the mass with warm water, sodium arsenate is dissolved and may be 

 filtered off, while antimonic oxide remains undissolved, and may be dissolved in 

 hydrochloric acid. Both solutions may now be used for making the respective 

 tests for arsenic or antimony. 



Antidotes. Moist, recently prepared ferric hydroxide or dialyzed iron are 

 the best antidotes, insoluble ferric arsenite or arsenate being formed. Vomit- 

 ing should be induced by tickling the fauces or by administering zinc sulphate, 

 but not tartar emetic. 



QUESTIONS. 291. Which metals belong to the arsenic group? what are their 

 characteristics? 292. Which non-metallic elements does arsenic resemble? 

 Mention some of the compounds showing this analogy. 293. How is arsenic 

 obtained in the metallic state ; what are its physical and chemical properties ; 

 how does heat act upon it? 294. What is white arsenic? State its compo- 

 sition, mode of manufacture, appearance, solubility, and other properties. 

 295. Which three solutions, containing arsenic, are official, and what is their 

 composition? 296. How is arsenic acid obtained from arsenous oxide, and 

 which arsenate is official? 297. State composition and properties of arse- 

 netted hydrogen, and explain its formation. What use is made of it in testing 

 for arsenic? 298. State the composition of realgar, orpiment, Scheele's green, 

 and Schweinfurth green. 299. Give a detailed description of the process by 

 which arsenic can be detected in organic matter. 300. Describe in detail the 

 principal tests for arsenic. 



