Chapter XVI: Part III: Science (3)

They proceed therefore to weigh their empty crucibles with the usual precautions and then to reweigh them after having put in some dry chalk. The numbers obtained are carefully entered in the laboratory note-book with which each girl is provided. The crucibles are then placed in a “muffle” furnace, which the pupils are taught to manage for themselves, and are only withdrawn at the end of the lesson and placed in desiccators to be reweighed at the beginning of the next lesson, when they will be again submitted to the same treatment until the weight is constant.

While the crucibles are being heated preparations are made for finding out the action of acid on chalk; the pupils are led to suggest a simple form of apparatus for measuring the volume and weight of the gas given off, and hence for determining its density. By the time this is done the hour and a half allowed for the lesson will probably have expired. At the next lesson, after a preliminary questioning as to what each pupil has done and is going to do, the apparatus decided upon at the previous lesson is carefully prepared; subsequently the actual experiments to determine the quantity of gas given off are performed and its density determined, and finally it is shown that the gas given off from chalk under the action of heat is identical with that released by acid, chalk being composed of this gas and the residue left after heating it in a muffle furnace until the weight is constant.

It will be seen that this work involves a considerable amount of weighing and calculation, but this is rendered easy by the previous grounding in elementary physics, and a series of experiments such as that described may be carried out intelligently by any properly trained class of girls.