100 



THE POPULAR EDUCATOR. 



the genitive, and by or for is required for the dative. The 

 subject and direct object are generally without a preposition 

 in English ; and when the Greek verb has its object in the 

 genitive or the dative case, the English idiom must be followed 

 in the translation, and not the Greek, except when the two corre- 

 spond. An English construction corresponding with the Greek 

 construction is to be preferred, when it can be had with the 

 preservation of perfect purity in the translation. After all, the 

 idioms of the two languages vary considerably, and it is possible 

 for a rendering in English to be too close to the original. Keep 

 as near as you can to the Greek, but never forfeit correctness in 

 the English. 



LESSONS IN CHEMISTRY. IV. 



CHEMICAL APPARATUS. In this lesson we shall give soma 

 practical hints concerning apparatus, and it will be found that 

 the general idea that chemical apparatus, etc., is very expen- 

 sive, is as erroneous as it is general. Indeed, most of the 

 prominent experiments, even for a lecture-room, may be per- 



Fig. 5. 



Fig. 6. 



Fig. 7. 



formed at the outlay of a few shillings. We shall enumerate 

 the several things which are all but necessary; but the in- 

 ventive student will soon find ways of adapting a very little 

 apparatus to many purposes. 



It is advisable that all bottles and breakable apparatus should 

 \>& kept in a room which can be set apart as a laboratory, or, 

 where this cannot be done, in a closet under lock and key. 



BLOW-PIPES. The most convenient mode of "heating" is 

 either by a "spirit-lamp" or bya"Bunsen's gas burner," 

 the name of each being smokeless. 



A Glass Spirit-lamp (Fig. 5o), with a ground-glass cap, which 

 fits on the wick when the lamp is not in use, and prevents the 

 evaporation of the spirit, costs Is. 4cZ. The wick-holder is stone- 

 ware, which is preferable to brass, as it does not corrode ; nor 

 does it conduct the heat of the flame to the body of the lamp, as 

 brass wick-holders do. A lamp of 5 or 6 oz. capacity is the 

 most convenient size. The spirit used is " methylated spirit," 

 the price of which is about 5s. per gallon. 



Bunsen's Gas Burner. In this kind of burner (Fig. 6) the 

 gas enters by the horizontal pipe, b, and escapes from a jet a 

 little above the holes in the neck into which the upright pipe 

 a is screwed. The gas thus mixes with the air, and burns with 

 a smokeless flame at the top of the pipe. When a broad surface 

 is to be heated, which is generally the case in evaporation, a rose 

 burner, d, is used. The smallest size of Bunsen's burner (2-inch 

 bore) is Is. 6d. ; with the rose Is. more. When a greater heat 

 is required we use a blow-pipe (Fig. 56), which is merely a tube 

 which ends in a very small hole through which a stream of air 



is blown upon a flame. A tin blow-pipe with brass nozzle costa 

 8d. Some practice is required before a steady, good flame 

 can be maintained ; this is accomplished by filling the mouth 

 with air, and continuing the pressure with the cheeks, while 



breath is taken through the nose. First practise without the 

 blow-pipe in the mouth, inflating the cheeks, and while inflated 

 breathe through the nose ; then, without opening the mouth, force 

 the blow-pipe between the lips, and it will be found that the 

 escape of air from the blow-pipe is so little that the former 

 process of breathing with inflated cheeks can be continued, 

 and thus a steady flame procured. 



Herapath's Gas Blow-pipe, the price of which is 7s. 6cf. (Fig. 

 7), is more convenient, especially for blowing glass, and for 

 fusions. The gas enters at a, and meets at b with a current 

 of air which is blown from c. The 

 flame, therefore, is like that of the 

 Bunsen's burner, smokeless, but 

 hotte and pointed. 



GLASS TUBING may be had any 

 size, from 2s. a pound. The three 

 smallest sizes will be found most 

 useful. If the tube be wanted for 

 combustion that is, to stand heat 

 without melting " Bohemian hard 

 glass " must be used ; it is not 

 dearer than the English. 



To Cut Glass Tubing. Take a 

 key-file, which may be obtained for 

 id., and make a mark across 

 the tube with the edge of the 

 file at the place where the tube is 

 required to be broken ; take hold 

 of it on each side of the mark, and 

 it will snap when pressed. If the 

 tube be large, the scratch must be 

 continued round the tube. 



To Melt or Bend Tubes. Simply put them in the blow-pipe 

 flame, being careful to do it by degrees ; then turn the tube 

 round, so that each part may be alike heated. The flame will 

 soon become tinged with yellow, which is the burning of the 

 soda in the glass, and proves that the glass is melting ; then 

 bend the tube to the shape required, but be careful not to allow 

 the hot part, when removed from the flame, to touch anything 

 cold, or it most probably will crack. 



To Blow o, Bulb. Hold the end of the tube in the flame (Fig. 

 8), and when it is soft touch it with another piece of tube. The 



Fig. 9. 



Fig. 10. 



two will adhere. Now twist the latter, and by this means the 

 hole in the first tube will be completely closed, or the tube will 

 be " hermetically sealed." Place this sealed end in the flame, 

 and continually turn it round, so that all sides may be equally 

 heated. Upon blowing through the tube this softened glass 

 will expand into a bulb. 



It is frequently required to pass tubes through corks. Thia 



