APPENDIX 327 



gain being held to represent the chlorine which has combined 

 with the zinc. How much chlorine would be required for one part 

 of zinc ? How much for one part of hydrogen ? 



EXP. 17. Brighten a piece of magnesium ribbon, and weigh 

 off exactly .04 grams upon a watch-glass. Place the magnesium 

 in a beaker, and cover it with a small, short-stemmed funnel, in- 

 verted in the beaker. Fill the latter with water. Fill a eudiometer 

 with water, cover its mouth with a bit of bibulous paper, so as to 

 be able to invert it, and set it so that its rim rests on the funnel 

 in the beaker, with the stem of the funnel projecting into the eudi- 

 ometer. Remove as much water from the beaker as possible without 

 exposing the open end of the eudiometer, and pour a considerable 

 amount of strong hydrochloric acid into the beaker, allowing it to 

 run down the walls, so as to form a layer at the bottom. It will soon 

 work its way to the magnesium, which will quickly dissolve, the dis- 

 placed hydrogen rising into the measuring tube. When the reac- 

 tion is completed, the beaker is again filled brimful, the eudiometer 

 slipped off the funnel, closed with the thumb and transferred to a 

 tall cylinder full of water, where it is allowed to remain for some 

 time. The barometer having been read, and the temperature of the 

 water in the cylinder having been noted, the eudiometer is lifted 

 until the water within it stands at the same level as that without, 

 and the volume of enclosed hydrogen is read off on the engraved 

 scale. The calculation of the corresponding mass will be explained 

 orally. 



EXP. 18. Weigh a porcelain crucible and lid, after cleaning 

 and drying them. Add about .8 gram of bright magnesium ribbon, 

 and weigh again. Set the crucible on a pipestem triangle, on a 

 ring-stand, and heat gradually without removing the lid, except- 

 ing for a moment or two at a time to admit fresh air, and observe 

 whether the magnesium has all been burned. Avoid the escape of 

 a white smoke. When all the magnesium appears to have burned, 

 remove lid and heat crucible more strongly. Cool, weigh crucible 

 with lid and contents. The gain in weight represents oxygen. In 

 what proportion did the two elements combine ? 



EXP. 19. Charge the hydrogen-generator with some zinc, and 

 replace the deli very- tube with a bent tube leading to a U-tube con- 



