32 DECOMPOSITIONS BY TERNARY ARRANGEMENTS. 



ed ; the water could find a ready passage through the serous membrane, but the col- 

 ouring matter could not. Now, on arriving at the under side of the membrane, the 

 water either was removed by uniting chemically with the alcohol, or by sinking me- 

 chanically through it to the bottom of the glass. Complete decomposition was effected, 

 all the colouring matter being retained above the membrane, and, on placing a candle 

 on one side of the glass and the eye on the other', dense striae of colourless water were 

 seen passing through the alcohol, but not a particle of the litmus escaped. 



98. Under this condition, those experiments which have been instituted to demon- 

 strate the passage of colouring matter through the lacteals have been made. The lac- 

 teals do not open into an intestine with patulous mouths, but their lining membrane of 

 serous tissue ends bluntly in a kind of cul-de-sac. Through such a membrane, litmus, 

 indigo, &c., cannot penetrate, though water may find a ready passage. Hence, be- 

 cause we cannot colour the chyle by an injection of litmus or indigo water, it is not to 

 be inferred that no medicine can pass from an intestine into the lymphatic system ; the 

 experiment now detailed goes to prove directly the reverse, and furnishes us with an 

 explanation of the uniformity of colour of the fluid in the chyliferous vessels. 



99. An important circumstance in gaseous analysis may here be noticed. If a tissue, 

 in the act of transmitting gas, or ready to do so, be placed in contact with another gas 

 of a different nature, disturbance immediately ensues. A cubic inch of nitrogen gas, 

 made with phosphorus, but which was found to be contaminated with 4^ per cent, of 

 oxygen, was agitated briskly in a vial containing about an ounce of spring water, such 

 as has been mentioned to contain a gas j oxygen. In one minute the nitrogen gained 

 one per cent, by the agitation. The same quantity of nitrogen gas, agitated in a pint 

 of water, gained no less than 11 per cent, of oxygen, which it had taken from the rich 

 gas of the water. Nor is agitation or mechanical violence necessary to produce this 

 important result. Into a bell filled with water, and inverted into another vessel, so as 

 not to touch it in any point, I threw 100 measures of a gas, 85 of which were oxygen. 

 After four weeks an analysis was made, and the gas in the bell found to contain only 72 

 per cent, of oxygen, the remainder being nitrogen. In this way, too, in the lapse of 

 time, from an inverted vessel, partially filled with atmospheric air, the oxygen will es- 

 cape into the water, and thence into the atmosphere ; and I have twice known this 

 event to take place, so that the residue did not contain more than three or four per 

 cent, of oxygen. In many of the most delicate researches of chemistry, we have this 

 disturbing cause in operation. Water is universally employed in our laboratories as a 

 means of confining gases ; it enters largely into our processes of pneumatic manipula- 

 tion ; and though we have hitherto neglected its action, it silently disturbs all our re- 

 sults. An air-bell cannot pass to the top of a jar without instant contamination : du- 

 ring its residence there it is subject to a continued succession of changes at no two 

 moments is it the same in composition a perfect freedom of communication existing 

 between it and the atmosphere. 



100. As an instrument of rigid analysis, the pneumatic apparatus, so arranged, requires 

 to be used with circumspection. It is" impossible to keep oxygen, nitrogen, or any other 

 gas in its original purity, if confined by water. This fluid, which, when reduced to a 



