274 J. L. Smith— Determination of the Alkalies in Silicates. 



bon arising from certain constituents in carbonate of ammonia; 

 tl\e quantity is usually very minute and in no way affects the 

 tv: curacy of the analysis. In selecting pure carbonate of am- 

 in mia for analytical purposes, it is well to take ! 

 are not colored by tlie action of light. 



It only remains now to separate the alkalies by the known 

 methods. Under this head I have made several observations, 

 that at some future time may be published as soon as the re- 

 salts are sufficiently definite. 



A special arrangement Jor heating the crucible by gas. — The 

 support and burner, where gas is to be had, are simple in their 

 character and have been contrived after a great variety of ex- 

 dth gas furnaces. The figure here given illustrates 

 nd, burner, crucible, &c., and is about one-sixth the nat- 



h is the stand with its rod g ; c? is a brass clamp with two 

 holes at right angle to each other having two binding screws; it 

 slides on the rod g; the second 

 hole is for a round arm attached 

 to b, the binding screw e fixing 

 it in any position. 5 is a plate 

 of cast iron five to six mm. thick 

 ten to eleven cm. long, and four 

 and one half cm. broad, having a 

 hole in its center large enough to 

 admit the crucible to witbm about 

 15 mm. of the cover, without bind- 

 ing, a is the crucible already re- 

 fen-ed to which is made to mcline 

 a few degrees downward hy turn- 

 ing the plate of iron that supports 

 it c is a chimney of sheet iron, 

 long, ten cm. 

 ; high, the width at the bottom be- 

 ■ • about 4 cm. at one end, anj 

 about three cm. at the other end. 

 It is made with the sides straight for about four cm., t*ien > 

 clines toward the top so as to leave the width of the op^^^"^'; 

 the top about one cm. A piece is cut out of the fron^/'^J^^ 

 chhnney of the width of the diameter of the hole m the i ^^^^ 

 support, and about four cm. in length, being semi-circular ai 

 top, fitting over the platinum crucible. Just above this pan ^ 

 the chimney is riveted a piece of sheet iron in the » oi ^ 

 liattened hook n which holds the chimney in place hy ^ ^_ 

 'the top of the crucible support ; it serves as a p^.^ 



>thec 



jible against the cooling of the currents ^ 

 n T. E. .TenkiQS & ( 



