OF CENTRAL CANADA PART I. 45 



other hand, the blowpipe alone is rarely sufficient for their detection. 

 This however, so far as practical purposes are concerned, is of little 

 consequence, as no economic value in silicates of this kind is depen- 

 dent on the base. 



A complete scheme for the detection of mineral bases by the blow- 

 pipe, does not fall within the province of the present work, but an 

 arrangement of the more important of these bodies, in groups, founded 

 on blowpipe characters, is given below. Before referring to these 

 groups, the unpractised operator is recommended to subject the speci- 

 men under examination to three or four simple experiments, and to 

 note down the results. These experiments comprise: 1, Ignition 

 in the bulb-tube, for detection of water. (This experiment may be 

 omitted as a general rule, if the substance possess a metallic lustre.) 2, 

 Treatment per se on charcoal or in the foreceps (see Operation 1, 

 page 30 above), the characters more especially to be looked for, 

 being coloration of the flame, formation of a coating on the charcoal, 

 assumption of magnetism, &c. 3, Treatment (after previous roasting 

 [Operation 4], if sulphur, &c., be present) with borax, phosphor-salt, 

 and carb. soda, respectively : observing if the glass be coloured, if the 

 substance dissolve entirely in it, if a reduction to metal take place, 

 and so forth (Operations 5 and 6, above). These experiments will 

 in general be sufficient to determine the nature of the base ; but 

 occasionally, certain special operations may be required in addition, 

 such as testing with nitrate of cobalt, or examination for mercury in 

 the closed tube, as described on a preceding page (Operations 3 and 6). 



SECTION 1. GIVING per se, OR WITH CARD. SODA, ON CHARCOAL, 



METALLIC GLOBULES OR METALLIC GRAINS. 



Group 1. Yielding malleable metallic globules, without deposit on 

 the charcoal. 



Gold. Silver. Copper. 



Gold is insoluble in the fluxes. Silver is not oxidized per se, but 

 retains a bright surface after exposure to an oxidating flame. Copper 

 becomes encrusted on cooling with a black coating. It imparts a 

 green colour to the flame-border ; and forms strongly coloured glasses 

 with borax and phosphor-salt : (green (hot) blue (cold) in O F ; red- 

 brown, opaque, in II F). Gold and Silver may be separated from 

 copper, &c., by fusion with lead, and subsequent cupellation (Opera- 



