M' Alpine & Hutchinson — On Vartry and Canal Waters. 79 



XIII. — Ox THE Gaseous Consxittjej^ts oe the Vaktey axd Geaxd 

 Ca>^al Waters. By Aechibaxd jN". M'Alpixe, B. Sc, Assoc. 

 E. C. Sc. I. ; and Chkis. Clauke IIIJTCHI^^sox, Eoyal Exhibitioner, 

 Eoyal College of Science. 



[Read, June 2-5, 187".] 



HiTHEKTo, in the examination of -waters for domestic purposes, the 

 attention of chemists has been almost entirely confined to the solid 

 bodies they contain in solution, scarcely any attention having been 

 paid to the gaseous substances present. 



That gases, like oxygen, when present in considerable quantities, 

 have no effect upon the human system appears unlikely. The Eight 

 Hon. Lyon Playf aii- believes that the medicinal properties of the mineral 

 waters of Buxton are due to the nitrogen they contain. '\\Tiether 

 these gases have, or have not, any action, we must leave to medical 

 men to decide ; but, at all events, it seems desirable that in the waters 

 examined for drinking purposes the oxygen contained in solution 

 should be estimated, as, from the quantity of this gas present in 

 waters, some clue might be afforded to the state or condition of the 

 organic matters they contain. 



With these objects in view, we undertook, at the suggestion of 

 Professor Galloway, the examination and estimation of the gaseous 

 constituents in the Vartry and Grand Canal waters which are sup- 

 plied to Dublin, and the neighbouring townships. 



"We conducted the examination and analyses in the following 

 manner : — 



A measured volume of the water under investigation was taken ; 

 the gases in this volume expelled, collected, and measured; their 

 quantities were determined, and the respective quantities of each 

 present were estimated, by the refined method of gas analysis devised 

 by Professor Bunsen. 



For the expulsion and collection of the gases we used the appa- 

 ratus proposed by Eeichardt, and described by Fresenius in the "Zeits- 

 chrift fiir analytische Chemie," vol. xi., p. 271. 



Some preliminary experiments were made upon the gases thus 

 obtained, to ascertain the quality of the gaseous mixture. After the 

 removal of the carbonic acid, by ineans of a potash bullet, and of the 

 oxygen by a coke bullet, saturated with pyro-gallate of potash, the 

 measured gas remaining in the eudiometer was exploded with a 

 measured volume of oxygen, and a detonating mixture of hydrogen 

 and oxygen, obtained by the electrolysis of water. I^o contraction 

 occui'red, other than that due to the detonating gas ; the potash bullet 

 was again introduced, and on measuring, the volume remained as before ; 

 hence, we inferred, since no carbonic acid had been formed, that 

 carbonic oxide and carburetted hydrogen were absent, and that the 

 gaseous mixtui'e consisted only of carbonic acid, oxygen, and nitrogen. 



