DR. E. FRANKLAND’S RESEARCHES ON ORGANO-METALEIC BODIES. 
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from a solid mass of the metal by a recently invented process. This Fig. 2. 
tube is closed at bottom by a screw plug", and is furnished at top with 
a brass flanch, B, B, If inch broad and 1 inch thick, screwed upon 
the copper tube : the vessel thus formed is closed by the brass cap C, C, 
of the same dimensions as the flanch upon which it fits. The cap is 
furnished with a central projection 1 inch deep, fitting the copper 
tube, and pierced with a central aperture D, tapped to receive the 
screw plug E, which, with the intervention of a collar of lead, effec- 
tually closes the aperture. Tlie cap C C is secured to the digester by 
three screw bolts | inch in diameter, which are inserted from above 
and screw into the lower flanch. Perfect impermeability to gases is 
secured, as in the iron digester, by a sunken annulus and a ring of ^ 
lead. When it is desirable to collect the gases evolved during any 
operation in this digester, the plug E is replaced by a carefully made 
stopcock, to the nozzle of which a gas-delivery tube can be attached, when the re- 
action is completed. This digester is heated by means of a cylindrical copper oil- 
bath placed in a gas-stove, as shown in fig. 3. The gas- 
stove consists of a strong wrought-iron framework, A, A, 
around which is fixed the sheet-iron cylinder B, B closed 
at the bottom, but furnished with a draught regulator C, 
and contracted at top by a ring of sheet iron so as just to 
admit the cylindrical oil-bath D, D, the flanch of which 
rests upon the upper extremities of the wrought-iron frame- 
work, which are turned inwards for this purpose. The 
sheet-iron cylinder is surrounded by another of polished 
tin plate to prevent the too rapid radiation of heat ; there 
is an interval of half an inch between the two cases, and 
both are pierced with holes at E for the exit of the products 
of combustion. A ^-inch copper pipe, F, pierced with 
eighteen or twenty small apertures, forms the gas-burner. 
By this arrangement, it is easy to maintain an almost con- 
stant degree of heat for any length of time. The tempera- 
ture is ascertained by the thermometery*, immersed in the 
oil-bath through an aperture bored in the cap and flanch 
of the digester for this purpose. This gas-stove is also 
used for heating the iron digester, but without the inter- 
vention of the oil-bath. In this copper digester, which is 
capable of resisting enormous pressure, it is easy to prepare 
four or five ounces of zincethyl at one operation. 
The zincethyl used in the experiments detailed below, was prepared in the follow- 
ing manner. The copper digester, well cleaned, dried, and heated to about 150°C., 
2 N 2 
