APPENDIX I 67 



ance of the village tinsmith, a very satisfactory still can be 

 cheaply put together. Instead of a straight condenser, it is 

 sometimes convenient to coil the tin tube into a spiral, 

 and place it in a tub of water with the end of the tube 

 coming through the side of the tub near the bottom. 



Experiment 16. With a little practice a very com- 

 plete separation of the sand and clay can be obtained 

 by this means. The process is the same as that used in 

 gold-washing, etc. 



Experiment 17. The diagram in the text shows a 

 very simple and cheap form of apparatus for drying sub- 

 stances at the temperature of boiling water. 



The dry, clean, empty dish should first be weighed and 

 the weight noted, then the soil introduced and the whole 

 weighed again. The dish of soil after drying must be 

 allowed to cool before being weighed again. It should 

 be placed to cool in a desiccator or under a bell-jar (see 

 Appendix II). 



Experiment 19. A crucible made of platinum, 

 while very suitable for this experiment, is somewhat 

 expensive. A porcelain crucible, or platinum tray made 

 by bending up the edges of a piece of platinum foil, will 

 do very well. If a crucible is used, it should be left 

 uncovered when over the flame and tilted a little on one 

 side, so as to let the air freely circulate. Where gas is 

 available it can be heated over a Bunsen burner. Where 

 gas cannot be obtained, the petroleum blowpipe should 

 be used. The pipeclay triangle is easily made. Three 

 pieces of iron wire about 6 inches long and a clay to- 

 bacco pipe are required. Break off the stem of the pipe, 

 three short pieces about 2 inches long, slip a piece of 

 iron wire through each, and then twist together the ends 

 of the iron wires, so as to make a triangular support for 

 the crucible, with the twisted ends of the wires resting on 

 the ring of the retort-stand. Such a stand will endure 

 a high temperature for a long time, and will not injure 

 the platinum, as a metal support would do. 



