562 MINERALOGY 



tion dissolve 139 gm. in a liter of water. It is used in the test for 

 nitrates. 



Cobalt nitrate, Co(N0 3 ) 2 . 10 gm. are dissolved in 100 cc. of 

 water. A supply is kept in a dropping bottle for use. Various 

 compounds after ignition in the O. F. with cobalt solution yield 

 characteristic colors, as alumina and zinc oxide. 



IDENTIFICATION TESTS OF THE ELEMENTS 



Included here are the blowpipe tests and the most important 

 chemical reactions used in the identification of minerals. The 

 order followed is to a large extent that of Mendeleeff s periodic 

 system. The common elements and therefore the most important 

 are placed first in each group. 



THE ALKALIES 



Sodium, Na ; Potassium, K ; Lithium, Li ; and the rare elements 

 Rubidium, Rb ; Caesium, Cs. 



Owing to the great solubility of all salts of the alkali metals there 

 is no simple direct test to prove their presence in a mineral in 

 the wet way. From a blowpipe standpoint they all agree in yield- 

 ing distinguishing flame colorations. When present only in small 

 amounts, as is generally the case of rubidium and caesium, the 

 spectroscope is necessary for their identification with certainty. 

 Salts of the alkali metals, except borates, phosphates, silicates, 

 and some salts of rare acids, when strongly ignited in O. F. yield 

 an alkaline reaction with turmeric paper. 



Example. Ignite some powdered sodium chloride, NaCl, 

 in the O. F. on platinum wire, moisten the wire and touch it to the 

 powder, when enough will stick to it for the test. Place on a clean 

 watch glass a small square, 1 cm., of turmeric paper. When the 

 ignited salt has cooled it is placed on the paper and a single drop of 

 water from a dropper is dropped on the ignited powder. The water 

 dissolves the alkaline salt, and on being absorbed by the paper 

 colors it reddish brown. In some cases it may be necessary to 

 allow the fragment to rest on the paper for a few minutes, when the 

 alkaline reaction will appear directly under the fragment, where 

 it is in contact with the paper. In salts that are not alkaline before 

 ignition the reaction is due to a decomposition of the salt by the 



