Protoxyd of Iron in Silicates. 349 
pulverized mineral (from one-half a gram to a gram) is weighed 
out in a large platinum crucible. Upon this we pour a mixture 
of dilute sulphuric acid (sp. gr. 15) with as little hydrofluoric 
acid as experience may show is required to dissolve* the mineral 
stirring up the material with a platinum spatula. The crucible 
is next transferred to the water bath, the covering tunnel put in 
. , water poured into the groove, the interior filled with car- 
nic acid from the generator and the gas lamp lighted. As soon 
as the water boils, the connection with the generator is closed, and 
} ifthe water level has been properly adjusted, the apparatus will 
7 take care of itself, the groove will be kept full of water and the 
Interior of the tunnel full of steam. If the materials cake on the 
bottom of the erucible,—as is not unfrequently the case when a 
large amount of insoluble sulphate is formed,—the lamp may be 
removed, the apparatus again filled with carbonic acid, and the 
Contents of the crucible stirred up as above described. A stout 
platinum wire about two inches long, cemented before the blow- 
Pipe to the end of a glass tube, makes an excellent stirring rod, 
and after using it any adhering material can easily be was ack 
into the crucible ‘by directing the jet from the wash bottle down the 
throat of the covering tunnel. ‘The lamp may then be replaced, 
the current of carbonic acid interrupted and the process of diges- 
tion continued. When the decomposition is complete the cur- 
tent of carbonic acid gas is reéstablished, the lamp extinguished 
| = 4nd the air tube of the Mariotte’s flask raised until its lower end 
| ‘above the level of the overflow. A slow current of water is 
thus caused to flow through the bath, which soon cools down 
the whole apparatus. The crucible may now be removed, its 
Contents washed into a beaker glass and the solution ge 
e 
"oe 4 ef ies : SO ee ee eo oe eee 
ci 
4 solution of permanganate of potassa in the usual way. 
amount of iron present being subsequently determined, the 
anate was tested with 
ach case 14 
Very large amount of hydrofluoric acid, four or five times as 
% i i } - G ¥ . 
Faesnte 2, ninersl contains lend, baryis, sizontis oe ares Time in. any. consiieabis 
“8g as the mineral is wholly decomposed. a, 
