APPENDIX 329 



by drop, until the liquid shows an acid reaction. Write the two 

 equations involved. The liquid in the crucible may now be evapo- 

 rated to dryness, and the product examined. 



EXP. 22. Counterpoise a beaker upon the scales and add 25 

 grams of a "normal" hydrochloric acid, one gram of which 

 contains .0365 grams of HC1. Warm this gently, set over a wire 

 gauze. Meanwhile, place something more than two grams of sodium 

 carbonate in a porcelain dish, and weigh (the weight of the empty 

 dish being unimportant). Carefully transfer this salt, a little at a 

 time, to the acid, by means of a horn spatula, until the liquid is 

 faintly alkaline. Reweigh the dish to find the amount of sodium 

 carbonate required to neutralize the acid. 



EXP. 23. Repeat experiment 22, using potassium carbonate in 

 place of sodium carbonate, and compare the two results. 



EXP. 24. Pour 100 cc. of calcium hydroxide into a clean flask. 

 Dissolve a quarter of a gram of sodium carbonate in half a test- 

 tubeful of water, and add just enough of this solution to the 

 flask to complete the precipitation. When a drop produces no 

 further precipitate, add a few drops of the calcium hydroxide; 

 filter and neutralize the filtrate with hydrochloric acid, noticing 

 whether there is any effervescence. Pour a few drops of acid upon 

 the precipitate on the filter and note the result. 



EXP. 25. Weigh a clean porcelain crucible. Add one gram of 

 potassium chloride and reweigh. Add 5 to 6 cc. of dilute sulphuric 

 acid. Heat gradually in fume-closet until dry; allow the crucible 

 to cool, and moisten the contents with a little more sulphuric acid; 

 evaporate to dryness. Remove crucible to pipe-stem triangle 

 supported on ring-stand and heat with Bunsen burner, but not 

 sufficiently to melt the salt. Cool and weigh. The crucible now con- 

 tains acid potassium sulphate, KHSO4. 



EXP. 26. Mix on a piece of filter paper about two grams of 

 solid ammonium chloride with about three grams of powdered cal- 

 cium oxide. Pour the mixture into a specimen tube and close the 

 latter with a perforated stopper, through which passes a straight 

 glass tube. Over this tube slip an inverted test-tube, to the mouth 

 of which a piece of moistened red litmus paper has been made to 



