W. Crookes on the Wax-paper Photographic Procees. 163 



of the dish, the liquid is to be returned into the bottle, (both the 

 nitric acid and the cyanid can be used several times,) the dish 

 rinsed out with water, and then well scrubbed in every part with 

 the brushes; afterwards it is to be washed several times in 

 common water, once with distilled water, and then placed in a 

 slanting position against a wall, face downwards, to drain on 

 clean blotting paper. 



11. The vessel in which the wax is melted, must be contrived 

 so as never to allow of its reaching a higher temperature than 

 212° Fahr., or decomposition of the wax might ensue. I have 

 found the most convenient apparatus to be, a tin vessel 15 inches 

 square and 4 inches deep, having a tray which holds the wax 

 fitting into it, about 1 inch deep. The under vessel is to be half 

 filled with water, and by keeping this just at the boiling tem- 

 perature, the wax above will soon become liquid. 



12. The best source of heat is that known as the gauze gas 

 burner, it being free from smoke or dust, and not liable to 

 blacken anything placed over it. It consists of a common argand 

 burner fixed on a rather low and heavy iron stand, which is sur- 

 mounted by a copper or brass cylinder 5 inches in height and 2 

 inches wide, having a piece of wire gauze of 900 meshes to the 

 square inch fastened over the top. By connecting this burner 

 by means of vulcanised indian rubber tubing to the gas pipe, it 

 can be moved about the table to any convenient position. The 

 mixture of gas and air formed inside the cylinder, is to be lighted 

 above the wire gauze ; it burns over this with a large and nearly 

 colorless but intensely hot flame. 



13. The most convenient form of iron is the ordinal box 

 iron, made hot by heaters inside; perhaps it might be improved 

 in shape by having the end not quite so pointed, but this is not 

 of much consequence. Some operators recommend facing the 

 bottom with a plate of silver; this is very expensive, and seems 

 to me to be attended with no advantage whatever. 



14. For the purpose of absorbing the excess of wax from the 

 surface of the sheet, I should recommend the ordinary white 

 wove blotting paper, medium thickness. But this is not suffi- 

 ciently free from impurities to serve either for drying the sensi- 

 tive sheets, or for filtering; for this purpose, the fine filtering 

 paper (not the Swedish) employed in quantitative chemical oper- 

 ations is the best. 



15. The distilled water being one of those substances upon 

 the purity of which success will in a great measure depend, it 

 will be found much safer to distil it on the premises, especially 

 as the quantity required is trifling. A convenient size for the 

 still is about two gallons ; it may be procured ready made, with 

 worm &c. complete, of any large dealer in chemical apparatus. 

 It will be found far more economical both in time and trouble, 



