OF CENTRAL CANADA PART I. 21 



effervescence which is produced by the liberation of carbonic acid from 

 these salts. The test acids chiefly used, are nitric acid and hydrochlo- 

 ric acid. These must be kept in well-stoppered glass bottles provided 

 with glass caps, as their fumes soon destroy cork, and are otherwise 

 highly corrosive and deleterious. For geological purposes (testing 

 calcareous rocks, &c.) strong hydrochloric acid diluted with about an 

 equal volume of pure water, is principally used. The small bottle in 

 which this is kept, may have a long stopper extending into the acid ; 

 and a little nest or wicker-work pocket may be provided for its recep- 

 tion near the upper edge of the specimen basket. In examining a 

 mineral with an acid, the substance should be reduced, in ordinary 

 cases, to a fine powder, and covered in a test-tube or small porcelain 

 capsule with a few drops of the acid, the latter being subsequently 

 warmed or brought to the boiling point over the flame of a small 

 spirit lamp. The following are some of the principal effects pro- 

 duced by this treatment : 



(a.) Simple solution : Example, gypsum, &c. 



(b.) Solution with effervescence and simultaneous evolution of a colorless 

 inodorous gas : Ex. carbonates generally. Some of these, as calc spar, mala- 

 chite, &c., dissolve with effervescence in cold and more or less dilute acid ; 

 but others, as dolomite or bitter spar, and carbonate of iron, only effervesce, 

 as a rule, in heated acid. Either acid may be used, except in the case of car- 

 bonate of baryta or strontia ; as with these minerals, strong hydrochloric acid 

 forms an insoluble coating of chloride of barium or strontium, by which the 

 further action of the acid is entirely prevented. If the acid be used in a 

 diluted state, however, this effect is prevented, chlorides of barium and 

 strontium being readily soluble in water. 



(c.) Partial solution, with separation of a gelatinous residuum : Ex. various 

 silicates : these are said to " gelatinize in acids." Boiling hydrochloric acid is 

 generally required to produce the effect. The gelatinous matter consists of 

 silicic acid or silica. Some silicates (Vesuvian, Epidote, &c.), which do not 

 gelatinize under ordinary conditions, exhibit the effect after fusion or strong 

 ignition. 



(d.) Partial solution, with separation of granular silica, ex. harmotome, 

 labradorite, &c. Boiling hydrochloric acid must be used, and the mineral 

 should be finely pulverized. 



(e. ) Oxidation and solution, or partial solution, with evolution of sulphuretted 

 hydrogen, known by its fetid odour. Example Most Sulphides. The effect 

 is most readily produced by boiling the mineral in powder with hydrochloric 

 acid. 



(/. ) Oxidation and solution, or partial solution, without odour of sulphuretted 

 hydrogen. Ex. red copper ore, native copper, native silver, and some other 

 I 



