POTASSIUM AND SODIUM. 
283 
together at right angles, in such a manner that by remov- 
ing a screw-plug from the end of each rectilinear piece, the 
passage through it may be cleared by passing into it a short 
rod of iron; in order that this process need not be often re- 
peated, the diameter of the pipes should be as great as con- 
venience admits of. 
The patentee next describes a modification of the preced- 
ing apparatus, wherein no pressure is required to overcome 
the resistance opposed to the current of ammonia by the 
fluid mass into which the induction-pipes of the preceding 
apparatus are immersed. In this modification, all the in- 
duction pipes stop short at the covers of the pots, except 
that of the open pot, which may be allowed, without much 
inconvenience, to dip below the surface of the water or other 
liquid intended to arrest the metallic vapours. 
The ammonia gas, in this case, urged forward by an in- 
considerable amount of pressure, comes into contact with 
the surfaces of the fused ingredients in the several pots in 
succession, until it is either decomposed and its nitrogen ab- 
sorbed, as in the preceding case, or escapes by the last 
eduction-pipe of the series; to prevent which, either the 
number of pots may be increased, or, what is better, each 
of the three should be furnished with agitators, moved by 
machinery or labour. When the latter arrangement is 
adopted, each pot should be furnished with a lofty conical 
cover, containing, at Jts apex, a stuffing-box, in which the 
axis of the agitator turns, and which is kept sufficiently cool 
by a stream of water running through a small cistern, which 
embraces the stuffing-box. With this apparatus, the fused 
ingredients may be either in a fluid, semi-fluid, or pasty 
condition. 
The patentee claims the making of the cyanides and fer- 
rocyanides of potassium and sodium; or, as they are called 
in commerce, prussiates of potash and soda, in any suitable 
apparatus, by passing ammonia (either pure or mixed with 
such other gases as do not prevent the desired result) over 
