1839.] 



On Chemical Tests. 



281 



ebullition, intumescence, vapours, odour, such as of sulphur, or garlic, 

 the latter indicating arsenic, decrepitation, fusibility, colour, &c. 



lxv. The same process and the same observation ofphenomena should 

 be repeated with fresh fragments of the mineral, fluxing them first 

 with soda, then with borax, and lastly with microcosmic salt, the 

 latter being a flux made of five parts of crystallized phosphate of soda 

 and two parts of phosphate of ammonia. The indications produced by 

 all these methods are given in a table at the end of this article; 

 and by comparing the phenomena observed in bis experiments with the 

 indications specified in the table, the experimentalist in all ordinary 

 cases will be able to identify the mineral or metal under examination. 



lxvi. If the substance should decrepitate, it may be inclosed between 

 two pieces of charcoal, and the flame be directed on it through a hole 

 in the charcoal made for the purpose. In the case of earthy minerals, 

 they may be wrapped in a piece of platina foil. 



lxvii. All phenomena occuring upon the use of chemical tests, and 

 appearances produced by the blew pipe, should be noted down im- 

 mediately in a memorandum book in regular methodical order. 



ANALYSIS OF MINERAL WATERS.* 



lxviiI. The following observations may perhaps be useful in direct- 

 ing the student's attention to a few of the leading points in the exami« 

 nation of mineral waters. 



lxix. In examining a mineral water, it is of importance to ascertain 

 its specific gravity, which gives some insight into the proportion of its 

 saline ingredienls. Mr. Kirwan (Essay on Mineral Waters, p. 145.) has 

 given the following formula for calculating the proportion of saline sub- 

 stances in a water of known specific gravity : " subtract the specific gra- 

 vity of pure water from that of the water examined, and multiply the 

 remainder by 1.4. The product is equal to the saline contents in a 

 quantity of the water denoted by the number employed to indicate the 

 specific gravity of distilled water. Thus, suppose the specific gravity of 

 the water = 1*079, and that of pure water = 1000 then 79. X 1.4- 

 110.6 — saline contents in 1,000 of the mineral water." It is advi- 

 sable to conjoin this method with the following: 



lxx. Evaporate a given weight, say 1,000 parts, to dryness, and 

 expose the residue for 24 hours to a temperature not exceeding 300 



* From Brande. 



