SS eee eee 
ON TEACHING CHEMISTRY. 303 
behaviour when heated on the water-bath in comparison with that of water, 
their behaviour when burnt, their behaviour when boiled together with 
water in a flask attached to a condenser, and their solvent action in com- 
parison with that of water should be ascertained. 
10. Having given an account of the origin, &c. of the various liquids 
examined, and having alluded to the presence of alcohol in beer and wine, 
demonstrate the separation of alconol from beer by distillation; then 
describe the production of alcohol by fermentation and carry out the 
experiment, first with sugar and yeast, then with malt; explain that yeast 
is an organism, and show it under the microscope and lantern photographs 
of it. Make several mixtures of alcohol and water and let the relative 
density of each be determined ; then exhibit a table of relative density of 
spirit solutions of various strengths. Let a measured amount of beer be 
distilled, have the distillate made up with distilled water to the bulk of 
the beer taken and let its density be determined; reference being then 
made to the table of relative densities, the strength of the alcoholic dis- 
tillate could be ascertained, and thus the amount of alcohol in beer would 
be determined. 
11. The behaviour of water when heated may now be further studied; 
attention having been called to the thermometer as an instrument which 
enables us to judge how hot or cold it is, water should be heated and the 
gradual rise of the mercury column noted and the steady position which 
it assumes when the water boils. In the same way boiling water should 
be allowed to cool and the fall of the mercury column noted; further 
cooling should then be effected by means of ice, so that opportunity might 
be given for the stationary position to be observed which the column 
eventually takes up and maintains so long as unmelted ice is present. 
Having specially directed attention to these ‘fixed points,’ describe the 
construction of the thermometer. Next let a quantity of water be dis- 
tilled from a flask or can having a thermometer in its neck, and Jet the 
steady position of the mercury throughout the distillation be observed. 
Also let water be frozen by means of a mixture of ice and salt; the 
‘temperature’ of the freezing mixture having been ascertained, the 
thermometer bulb should be inserted into the water which is being frozen 
(in a test tube), so that the ice may form around its bulb: the temperature 
should be noted during freezing and also during the subsequent melting 
of the ice. Do this out of contact with the refrigerating mixture, 
12. Let the relative density of ice be determined, i.e. after showing that 
althongh ‘lighter’ than water ice is ‘heavier’ than turps, let a cylinder 
partly filled with turpentine be counterpoised, and after the temperature 
has been lowered by immersing the cylinder in ice water, note the position 
of the turps, then introduce a few pieces of dried ice, note the rise of the 
turpentine—thereby determining the volume of the ice—and subsequently 
weigh in order to ascertain the weight of ice introduced. Have the result 
thus obtained checked by subsequent observation of the bulk of water which 
results when the ice melts. The expansion of water on freezing having 
thus been observed, the bursting of pipes in winter may be explained ; and 
attention may also be directed to the destructive effects on rocks produced 
by the freezing of water ; the extent to which ice floats may be discussed, 
and arithmetical problems may be set which will lead the pupils to realise 
the extent to which the volume changes when water changes its state. 
13. Let the relative density of water and the other liquids be deter- 
mined at 6° C. and at a higher temperature—that at 0° by weighing and 
