LESSONS IN ARITIIMKTir. 



K.I 



may bo done by making a wire rather leu than the tube red- 

 hot, and tlu-n burning a hole through the cork. But by far the 

 beat plan in to buy " cork-borers," which are pieces of thin brass 

 ul u UK-, the edge of 

 which ia sharpened at 

 one end. They are 

 made in acts which fit 

 into each other. A 

 not of two costs lOd. ; 

 three, Is. 2d. There 

 are seta of six, but 

 those of two or three 

 answer every practical 

 I>urpoae. 



t tubes arc in con- 

 stant requisition ; their 

 sizes range from two 

 inches in length and a 

 quarter of an inch in 

 diameter, to eight 

 inches in length and 

 one and a-half inches 

 diameter. Their prices 

 vary usually from 4d. 

 a dozen to 3s. 



When they have 

 been used as with all 



chemical apparatus they should be cleaned. This is best effected 

 by a round brush, made of bristles held in twisted wire, which 

 costs 3d., or a piece of tow at the end of a wire will answer the 

 same purpose. 



It is convenient to have a stand, such as is shown in Fig. 10, 

 in which to hold test tubes. The stand may be bought for Is. 9d. 



Fig. 11. 



Of GLASS JABS (Fig. lla), one ought to be graduated as a 

 measure an 8 oz. " measuring glass " is Is. 8d. " Beakers " 

 may be had with spouts, but if not, then a glass rod must be 

 held at the place over which the liquid is to run, as in Fig. 9. 

 Jars are required for collecting gases ; those in which confec- 

 tioners keep 



-wni'M MiniiiTv their sweets are 

 1 d /T' lltov the best ; wide- 



necked bottles 

 also used by 

 them are very 

 cheap, and an- 

 swer every pur- 

 pose. 



FLABKB, which 

 also serve for 

 retorts, may be 

 had of any gro- 

 cer or oilman, 

 either for no- 

 thing or for a trifling sum. They come from Italy, filled with 

 olive oil. The glass flasks are chiefly made at Florence hence 

 their name, Florence flasks ; they are covered with rushes, not 

 only for their preservation, but that a flat bottom may be pro- 

 Tided on which they stand. For chemical use the rushes are cut 

 off, and the flask cleaned with a little soda and warm water. 



Flaiks with flat bottom* are required, and these may be had for 

 4*. 6d. a dozen, baring a capacity of 12 o*., 64. lees a dozen for 

 each 2oz. less in capacity, and <W. more for every additional 4 01 



One of these latter 

 faeirs may nuke a 

 very useful appentas 

 a wcuk bottle (Pi*. 

 11 b). By blowing 

 down the open pipe at 

 A, a jet of water ieraee 

 from the other at , 

 which i a convenient 

 mode of filling a test 

 tube, or adding a little 

 water to a solution. 

 To make this bottle 

 will be a good begin- 

 ning for a student, as 

 the tubes and cork 

 must fit tightly. 



A Ring Stand (Rf . 

 11 c), with three rings, 

 is 5s., and is indis- 

 pensable in the labo- 

 ratory. They may be 

 had larger, but this is 

 quite sufficient. 



Evaporating Basins (Fig. lid) are shallow basins of Berlin 

 porcelain. A nest of seven, containing from 1 J oz. to 18 oz., 

 may be had for 6s. 5d. 



Thuringian porcelain is thinner, and basins of this, more 

 shallow than the last, are in nests of nine for 6s. 



Distillation is carried on by turning a liquid into vapour, and 

 condensing this vapour again into liquid. A very useful con- 

 denser is the one shown in Fig. 12, Liebig's Condenser, price 14. 

 and upwards, a 6 is a glass tube, which passes through cold 

 water held in the larger tin tube c ; instead of the retort d, a 

 Florence flask may be used, the tube which passes through a 

 cork fitted into a being attached to its neck. The distilled 

 liquid falls from the pipe e into the vessel /. The water in the 

 coudenser is kept cool by continually renewing it ; the cold 

 water entering from the barrel g by the funnel i ; and, as warm 

 water always rises, the warmest escapes by the pipe h. 



Liquids are often purified by filtering (Fig. 13) ; for this fun- 

 nels of glass or porcelain are used, and white blotting paper is 

 cut into a round disc, then folded thus, a, and again into half, 

 h, opened, c, and placed in the funnel, d. The arrangement in 

 this figure is simple and convenient. 



We advise students not to lay in a stock, but to get chemicals 

 and apparatus as they are needed. The prices of preparations 

 will be found in catalogues, which will be forwarded by any 

 working chemist. 



All acids must be kept in stoppered bottles, and no bottlt 

 should be without a label descriptive of its contents. 12 OK. 

 bottles, with ground-glass stoppers, are 6s. a dozen ; Is. more 

 per dozen for each additional 4 oz. 



Fig. 13. 



LESSONS IN ARITHMETIC. XXVII. 



COMPOUND DIVISION. 



11. THE process of dividing a compound quantity may be 

 regarded in two aspects. 



(1.) We may divide a compound quantity by an abstract 

 number; that is, we may divide the compound number into 

 a given number of equal parts, and thus find the magnitude of 

 one of these parts. 



(2.) We may divide a compound quantity by a compound 

 quantity; that is, we may find how many times one given 

 compound quantity is contained in another. 



Thus J6U 10s. 6d. = 7 times i Is. 6d. 



Therefore .14 10s. 6d. divided by the abstract number 7 

 gives as a result 2 Is. 6d. Here we have shown that il 

 .14 10s. 6d. be divided into 7 equal parts, the magnitude of 

 each part is 2 Is. 6d. 



Again, 14, 10s. 6d. divided by 2 Is. 6d. gives 7 ae 

 quotient. This is the same as saying that .14 10s. 6d. contains 

 2 Is. Gd. 7 times. 



Hence we see that a compound quantity divided by an abstract 



