J. P. Cooke — New Mode of Manipulating Hijdric Sulphide, 431 



covering and uncovering the slits, when the handle E is turned. 

 To the lower end of the same shaft is fastened the agitator O, 

 which is turned simultaneously with the arms just mentioned 

 After the apparatus has been charged, it is evident that by 

 turning the handle the sulphide of iron may be sifted down at 

 pleasure into the acid water below ; and the handle and arms 

 are so disposed that when the bungs are uncovered by the han- 

 dles the slits are covered by the arms. From the generator, 

 the gas passes through the washer E, whose relations to the 

 s, us well as that of the pressure gauge, are evident 

 from the figure. The generator is lined with lead, and the rest 

 of the apparatus, including the bell-metal plate M, with pure tin. 

 The lead lining of the generator is seamless and very heavy, 

 and all the cocks are lined with block tin tubing. Of the vari- 

 ous valves, bungs, and stuffing boxes indicated in the figure, it 

 is unnecessary to speak in detail. It is sufficient to say that 

 they are of excellent workmanship, and during a year's trial 

 have kept perfectly tight. The charging bung, B, however, is 

 closed by a safety'cap of peculiar construction, which deserves 

 ention, because it insures the safety of the apparatus. 

 The cap is represented by Fig. 3, and a section is given i "' 



It will be seen by the last that the escape of the compressed gas 

 from the generator through the apertures d is only prevented l>v 

 a thin disk a, which is shown in detail by Fig. 5. This disk is 

 made of two thin plat. - : the lower one, which comes in contsurt 

 with the acid spray, is of lead, and the upper one of silvered 

 copper, whose thickness is so adjusted that it must be at once 

 ruptured if the pressure in the apparatus should become unduly 



Although the so-called soda-water fountains— in which the 

 solution of the gas and water is made— have all in general the 

 same simp] they are constructed of very -af- 



ferent materials and after very different methods. The outside 

 shell may be either of hammered copper or of some form of 

 iron, and this may be lined with tin, enamel, or glass 

 having determined by experiment that a solution of hydnc 



