CHAPTER VIII. 



TESTING BY THE WET PRWESS. 

 Systematic Plan of Procedure. 



IN testing a mineral by the wet process, the method is to 

 powder and thoroughly dissolve it in some liquid, usually 

 an acid, or mixture of acids, and then to recognise the 

 presence of some known metal or metals by the peculiarity 

 of the precipitate produced, when a reagent has been added 

 to the solution. If the mineral is likely to contain sulphur 

 or arsenic or other such volatile substances in its composi- 

 tion (such as iron pyrites, copper pyrites, galena, &c.), a 

 good plan is to powder and roast it in order to drive off the 

 sulphur, and to leave the metallic portions in the form of 

 oxide, and thus in a proper condition for easy examination. 

 There are certain minerals, as graphite, cinnabar (the prin- 

 cipal ore of mercury), some oxides, sulphates, chlorides, and 

 a number of silicates, that are not soluble in acid. So as to 

 simplify the testing of such as these, it is just as well to add 

 to the powdered mineral about four times the weight of 

 carbonate of soda, and to melt them in a crucible or other 

 apparatus, so as to leave the metallic portion in a condition 

 to be dissolved by hydrochloric acid ; but let it be remem- 

 bered that the above methods are only suggested to render 

 the tests more accurate than they would otherwise be. 



Notwithstanding that the blowpipe tests are those chiefly 

 to be depended upon, the following wet ones may be of use 

 in determining the presence of some of the metallic bases in 

 many of the common ores met with ; and the apparatus 

 required is not very large, consisting of three acids (hydro- 

 chloric, nitric, sulphuric), potash, ammonia, protochloride of 

 tin (if convenient) for the gold test, copper, and zinc, a few 

 test tubes, porcelain capsules, &c.* The principal objec- 

 tion to the wet process is the inconvenience of carrying 



* Also citric acid ; sulphate of iron for gold test, &c. 



