J. P. Cooke — New Mode of Mai 



the apparatus is complicated, and that the process requires 

 abor, it may be stated that in this laboratory the appa- 

 ratus is entirely in charge of a laboratory servant, and may be 

 managed by any workman of ordinary intelligence. It does 

 not require more than four hours to work over a single charge, 

 and this yields seventy-five liters of hydric sulphide solution 

 under a pressure of 120 pounds. According to our experience, 

 this supply lasts with a class of our hundred students in quali- 

 tative analysis about a month. For laboratories where the 

 classes are much smaller than this, we should recommend the 

 smallest size generator, which may be used with a single six- 

 gallon fountain. The smaller apparatus is managed in pre- 

 cisely the same way as the larger, only taking one half the 

 quantity of materials. It is important as before to wash out 

 in the first place all the air. and to maintain a small current of 

 gas through the vent valve of the fountain while the pressure 

 •hi the apparatus is rising. This of course eDtails some loss of 

 livdrie sulphide ; but the chief loss is caused by the venting of 

 the generator, and all this gas may be utilized for the prepara- 

 tion of alkaline sulphides as described above, or this waste gas 

 may be used for washing out the air from a second fountain, 

 and thus preparing it for a subsequent charge. 



For dispensing the reagent in our quulitutw: laboratory, we 

 place the fountain in a cupboard and connect it by a block-tin 

 tube with a so-called " draught column," 

 Fig. 7, in the ventilating hood above. 

 From this each student draws the reagent 

 as it is required. In quantitative work 

 we may draw the eh 

 from the fountain into the midst of the 

 solution to be treated, using simply a com- 

 mon rubber hose terminated by a glass 

 tube which dips under the surface of the 

 liquid : the hose is attached to the nipple 

 of a cap which screws on to the valve of 

 the fountain, and by confining two or 

 more disks of linen cloth between the cap 

 and the head of the valve (like washers) 

 we can filter the solution as it flows out. 

 It is more convenient, however, to distrib- 

 ute the reagent to advanced students in 

 the well-known soda-water siphon, Fig. 8. 

 These require no description, but as the 

 simple apparatus used for filling the siphon 



familiar object 



■ ,. u rs. from trhe catalogue of John 



laboratories, we give a figure of the apparatus (Fig.^ 9), take 



