NOTES. 179 



( 22 ) Page 100. Paper prepared like gun cotton. It 

 should be bibulous paper, and must be soaked for ten 

 minutes in a mixture of ten parts by measure of oil of 

 vitriol with five parts of strong 1 fuming nitric acid. The 

 paper must afterwards be thoroughly washed with warm 

 distilled water and then carefully dried at a gentle heat. 

 The paper is then saturated with chlorate of strontia, or 

 chlorate of baryta, or nitrate of copper, by immersion in 

 a warm solution of these salts. (See Chemical News 

 Vol. I. page 36.) 



LECTURE VI. 



( 23 ) Page 145., Sulphindigotic acid. A. mixture of 

 one part of indigo and fifteen parts of concentrated oil of 

 vitriol. It is bleached on the side at which hydrogen gas is 

 evolved in consequence of the liberated hydrogen with- 

 drawing oxygen from the indigo, thereby forming a colour- 

 less deoxidised indigo. In making the experiment, only 

 enough of the sulphindigotic acid must be added to give 

 the water a decided blue colour. 



( 24 ) Page 147. Lead tree. To make a lead tree, pass 

 a bundle of brass wires through the cork of a bottle, and 

 fasten a plate of zinc round them just as they issue from 

 the cork, so that the zinc may be in contact with every 

 one of the wires. Make the wires to diverge so as to 

 form a sort of cone, and having filled the bottle quite 

 full of a solution of sugar of lead, insert the wires and 

 cork and seal it down, so as to perfectly exclude the air. 

 In a short time the metallic lead will begin to crystallise 

 around the divergent wires, and form a beautiful object. 



THE END. 



