PROFESSOR GRAHAM ON THE MOTION OF GASES. 
609 
5. Transpiration of different Gases bp a Capillary Tube of Copper. 
It appeared desirable to have experiments on the passage of gases through tubes 
of different materials, in order to ascertain how far the coefficients of transpiration 
observed are peculiar to glass. After some trials, a capillary tube of copper was 
constructed, of a fine smooth bore, not wider than an ordinary thermometer tube, and 
indeed less in diameter than the preceding glass capillary H. This tube was formed 
by first drilling a cylindrical hole in the axis of a solid copper rod, 4 or 5 inches 
in length, and extending the latter afterwards by drawing it through a wire-plate. An 
iron wire, or triplet, was placed within the copper tube and drawn through the wire- 
plate at the same time, in order to keep the interior surface of the copper tube smooth 
and uniform. It was necessary to pull out the iron-wire always after the copper was 
drawn through the plate, to prevent the former being fixed. The iron-wire was then 
extended somewhat separately, and again introduced into the copper tube, and the 
operation of drawing out the latter repeated. In this way the copper tube was ex- 
tended to a length of 1 1 feet 8 inches. It was found to be perfectly sound and air- 
tight ; and allowed 1 cubic inch of air to pass into a vacuum in 22*12 seconds. 
Of the iron wire, upon which the copper tube was last drawn, 92*7 inches weighed 
18*30 grains; or 1 inch 0*1974 grain. Taking the specific gravity of iron at 7'7, 
this gives as the diameter of the copper tube 0*0114 inch, or ^ 8 -th of an inch. 
When used as a transpiration tube it was coiled up into circles of about 10 inches in 
diameter, and the ends joined by soldering to two block-tin tubes provided with 
screws by which they could be attached to the aspirator-jar and drying tube. 
The experiments were conducted precisely in the same way as with a glass tube, 
except that oil of vitriol was avoided and chloride of calcium only used in the drying 
tube. The following series of results were obtained with the copper capillary. 
Table XXV. — Transpiration by a Copper Capillary Tube into a one-pint jar. 
Barom. 29*97- Temp. 58°. 
Gauge barometer in inches. 
Air. 
Oxygen. 
Nitrous oxide. 
Carbonic acid. 
Air. 
I. 
II. 
I. 
II. 
I. 
II. 
I. 
II. 
I. 
// 
" 
✓/ 
// 
✓ / 
// 
II 
28 
0 
0 
0 
0 
0 
0 
0 
0 
0 
20 
234 
233 
260 
261 
198 
198 
199 
199 
234 
12 
291 
292 
324 
324 
244 
244 
245 
245 
292 
8 
206 
205 
228 
228 
170 
170 
171 
170 
204 
4 
333 
335 
372 
373 
275 
277 
276 
276 
336 
2 
342 
344 
387 
390 
283 
285 
287 
288 
344 
From 28 to 4 inches ... 
1064 
1065 
1184 
1186 
887 
889 
891 
890 
1066 
4 K 
MDCCCXLVI. 
