DE. E. EEAJN’KLAM)’S EESEAECHES ON OEGANO-METALLIC BODIES. 
61 
the gas being thoroughly dried, by bubbling through a long series of bulbs filled with con- 
centrated sulphuric acid, which also served to absorb any traces of nitrous gas that might 
be formed by atmospheric oxygen gaining access to the interior of the apparatus. The 
gas was conducted into the flask by a tube which terminated just below the cork ; whilst 
a provision was made for its exit by another tube continued to within a short distance of 
the surface of the liquid, and which terminated outside the cork in a capillary extremity, 
that could be readily sealed up by the blowpipe and reopened at pleasure. Binoxide of 
nitrogen, prepared from copper turnings and nitric acid, always contains a considerable 
per-centage of protoxide, and it was therefore necessary occasionally to allow a stream of 
the gas to flow through the flask, so as to prevent the absorption being hindered or stopped 
by the accumulation of protoxide of nitrogen : at other times the exit tube was herme- 
tically sealed and the gas supplied only as it was absorbed. In this way, although the 
apparatus was in action day and night, six weeks elapsed before the absorption was com- 
pleted. On another occasion, when the action was accelerated by violent agitation of 
the liquid for several hours each day, the zincethyl was saturated in about a fortnight. 
It was evident that such a process was little calculated for the production of con- 
siderable quantities of the new compound, and recourse was therefore had to mechanical 
means in order to expedite and facihtate the operation. Fig. I is from a photograph 
of the apparatus employed for this purpose, and as it will no doubt prove useful in other 
cases for experiments with sparingly soluble gases, I ■will describe it somewhat in 
detail. A is a copper digester similar to the one I have 
already described for the preparation of zincethyl * ; into 
the aperture h is screwed the stopcock c, to which can 
be attached at pleasure the condensing syringe D made 
of gun-metal, 12 inches long and ‘7 inch in diameter. 
In this syringe a solid steel piston If inch deep works 
au’-tight, and the piston-rod passes through a stuffing- 
box f. The syringe is supplied with gas through the 
nozzle e, to which a flexible tube is attached. When 
the stopcock c is closed, the elevation of the piston pro- 
duces a vacuum, which is instantly filled with gas, so 
soon as the piston has passed the nozzle e. Between e 
and/ the interior of the syringe is grooved longitudinally, 
so as to prevent any compression of gas behind the 
piston, when it is drawn up to f. On forcing down the 
piston and opening the stopcock c, it is ob'vious that the 
gas occupying the s^Tinge from e to c will be forced 
into A. By repeating this process, it is not difficult for 
one operator to compress about twenty atmospheres into A ; such a degree of compres- 
sion exerting upon the piston a pressure of about II41bs. 
* Philosophical Transactions, vol. cxlv. p. 261. 
Eig. 1. 
MDCCCLVII. 
E 
