334 APPENDIX 



EXP. 59. Treat some litharge (PbO) with dilute nitric acid 

 until dissolved. Test a portion of the solution with hydrochloric 

 acid. 



EXP. 60. Place a few grams of "red lead" in a test-tube, half 

 fill the latter with cold dilute nitric acid and shake. Filter the solu- 

 tion from the brown residue, and test the former with a few drops of 

 hydrochloric acid. What has gone into solution? What is the brown 

 residue ? What can we conclude as to the nature of "red lead" ? 



EXP. 61. Add hydrochloric acid to 10 cc. of lead acetate solu- 

 tion, in a test-tube, as long as a precipitate continues to form. Al- 

 low the latter to settle, pour off the clear liquid, shake the precipi- 

 tate with about 10 cc. of fresh water, allow to settle and pour off 

 water. Repeat this washing and then half fill the test-tube with 

 water, heat to boiling and filter, if necessary, into a clean test-tube. 

 It is well to have the filter ready in advance, as the liquid must be 

 filtered boiling hot. Cool the clear filtrate by running water over the 

 outside of the test-tube. 



EXP. 62. Precipitate 10 cc. of lead acetate with potassium 

 iodide and proceed as in Exp. 61. 



CHROMIUM AND MANGANESE 



EXP. 63. Render chromium sulphate solution alkaline with 

 potassium hydroxide. 



EXP. 64. Acidify chromium sulphate solution, and note whether 

 hydrogen sulphide gas affects it. 



EXP. 65. Acidify some potassium chromate solution, pass in 

 hydrogen sulphide until the test-tube smells strongly of the gas, 

 filter and add potassium hydroxide to the filtrate. 



EXP. 66. Add sulphuric acid to 15 cc. of potassium chromate 

 solution in a dish until the color has changed completely. Evapo- 

 rate until crystals commence to form. Then set aside to cool. 



EXP. 67. Add potassium chromate to lead acetate. 



EXP. 68. Mix a little manganese dioxide with sodium car- 

 bonate powder on a porcelain crucible-lid. Set on a pipe-stem 

 triangle and heat until the mass is fused. Cool, set in a beaker, dis- 



