114 PROCEEDINGS OP THE AMERICAN ACADEMY 



the air, is inconveniently dilute ; and two years since we described a 

 simple method by which a solution concentrated under pressure could 

 easily be prepared with the ordinary laboratory appliances. A heavy 

 glass bottle of about four litres' capacity served as a generator, and 

 from this the gas passed through a wash-bottle into two other bottles 

 of the same size and strength as the first. The intermediate bottle 

 was three-fourths filled with water, while the last served simply as 

 a gasholder. The connections were so arranged that the gas, after 

 bubbling up through the water, was delivered at the top of the gas- 

 holder ; and, by a tube uniting the bottom of the gasholder with the 

 water-pipes of the laboratory, the interior of the apparatus could be 

 submitted to the pressure of a column of water sixty feet high. The 

 gasholder was also provided with an exit tube, which could be closed 

 by a compression cock. The connecting tubes all passed through 

 rubber stoppers which were firmly wired to the necks of the bottles, 

 and the water-bottle was connected with its neighbors by two lengths 

 of stout rubber hose so that the water could be shaken up with the 

 gas without disturbing the rest of the apparatus. In order to saturate 

 the water with hydric sulphide, a charge of ferrous sulphide sulphuric 

 acid and water sufficient to yield at least three times the amount of 

 gas theoretically required was placed in the generator, and, after the 

 connections were made, the gas was allowed to stream through the ap- 

 paratus until all the air was displaced. The exit tube of the last bottle 

 was then closed, the water pressure turned on and the water-bottle 

 frequently shaken, until absorption ceased, and the aqueduct water — 

 at first forced by its pressure into the gasholder — was driven back 

 into the pipes. Before dismounting the api^aratus, the rubber connec- 

 tors were all closed by compression cocks, and care was taken to vent 

 the generator gradually. Moreover, the connectors of the water-bottle 

 were so arranged that when the apparatus was dismounted a short 

 piece of rubber hose was left attached to each orifice of the bottle, 

 both of which were closed by compression cocks. To one of these a 

 vent tube was subsequently attached, and by this the solution was 

 drawn off at pleasure, as from a soda-water siphon. 



This simple apparatus was constantly used by us for two years, and 

 served an excellent purpose ; but it was found that after the glass 

 genei'ators had been charged several times they were liable to burst 

 under the same pressure which at first they had readily sustained. The 

 same accident never happened to the other bottles. But of course, if 

 the pressure is long continued, bottles of glass of the size named, 

 however well made, would be liable to such an accident ; and, if the 



