394 On the Method of Assaying Silver. [No. 4, 



8. Hot air plate : of thin sheet iron bored with holes for the 

 reception of the crucibles, raised by iron feet about 1£ inches above 

 the furnace plate. It is furnished with a square tin cover which fits 

 over it. This is provided with lateral apertures for the escape of 

 heated air, and with a tube from its roof for the reception of a ther- 

 mometer. 



The drying furnace on which the above rest is surmounted by a 

 hood, the door of which (glazed) slides up and down by weights 

 and pulleys ; the plate is heated by means of gas jets ; it has a good 

 draught, to carry off the nitrous fumes, as on it the musters are 

 dissolved in the first instance on a sand bath. 



9. The forceps for removing the cake of chloride from each cup 

 to the skiff of the balance should not be too sharp in its grasp, it 

 is much improved by having the blades tipped for about an inch 

 from the points with platinum about £ inch in width. 



10. It is a convenience to have the assay weights arranged in 

 a set of ivory compartments in the weight box ; on the floor of 

 each compartment are engraved the figures corresponding to those 

 engraved on the weight which occupies it ; by this means the 

 assay er has merely to glance at his weight box to see what weights 

 are in the pan of the balance, and to read off the " touch" when 

 each chloride is counterpoised. 



Description of the Figures. 



No. 1. The fluid being syphoned from the bottles; those in a 

 slanting position on the turn-table have been syphoned for the last 

 time, and the chloride is being thus caused to collect to one spot. 



No. 2. The bottles in position in the trough — so as to let the 

 chloride fall into the cups underneath the water. 



No. 3. An assay bottle — in natural size — in which the sample 

 is dissolved and the chloride of silver precipitated. 



No. 4. Wedgwood cup in which the chloride is received, 

 broken up and dried. 



