In order to carry out the work indicated above there will be required several pieces of apparatus. First a small chemical balance; one that will carry 50 grammes in each pan is quite large enough, and such a one, quite accurate enough for this work, can be bought for 25s. to 30s., while if the dyer be too poor even for this a cheap pair of apothecaries' scales might be used. It is advisable to procure a set of gramme weights and to get accustomed to them, which is not by any means difficult. In using the balance always put the substance to be weighed on the left-hand pan and the weights on the right-hand pan. Never put chemicals of any kind direct on the pan, but weigh them in a watch-glass, small porcelain basin, or glass beaker (which has first been weighed), according to the nature of the material which is being weighed. The sets of weights are always fitted into a block or (p. 212) box, and every time they are used they should be put back into their proper place. The experimenter will find it convenient to provide himself with a few small porcelain basins, glass beakers, cubic centimetre measures, two or three 200 c.c. flasks with a mark on the neck, a few pipettes of various sizes, 10 c.c., 20 c.c., 25 c.c. The most important feature is the dyeing apparatus. Where only a single dye test is to be made a small copper or enamelled iron saucepan, such as can be bought at any ironmongers may be used; this may conveniently be heated by a gas-boiling burner, such as can also be bought at an ironmongers or plumbers for 2s. [Illustration: Fig. 33.--Experimental Dye-bath.] It is, however, advisable to have means whereby several dyeing experiments can be made at one time and under precisely the same conditions, and this cannot be done by using the simple means noted above. To be able to make perfectly comparative dyeing experiments it is best to use porcelain dye-pots (these may be bought from most dealers in chemical apparatus), and to heat these in a water-bath arrangement. The simplest arrangement is sketched in figure 33; it consists of a copper bath measuring 15 inches long by 10-1/2 inches broad and (p. 213) 6-1/2 inches deep; this is covered by a lid on which are six apertures to take the porcelain dye-baths. The bath is heated by two round gas-boiling burners of the type already referred to. The copper bath is filled with water which, on being heated to the boil by the gas burners, heat up the dye-liquors in the dye-pots. The temperature in the dye-pots under such conditions can never reach the boiling point; where it is desirable, as in some cases of wool mordanting and dyeing that it should be so high, then there should be added to the water in the copper bath a quantity of calcium chloride, which forms a solution that has a much higher boiling point than that of water, and so the dye-liquors in the dye-pots may be heated up to the boil.