BAIRD &.TATLOCK (LOM)ON) LTD. 



Laurent's Saccharimeter and Polariscope. 



DESCRIPTION OF THE APPARATUS. 



GAS BURNERS. 



Two burners are constructed, one for high and one for low pressure, and it is necessary to indicate which is required when 

 ordering. 



To measure the pressure of the gas take a glass U tube and half fill it with water. One limb is open and the other is connected 

 with a gas tap, and on opening this the gas causes the water to descend in one limb and ascend in the other ; the difference of 

 level is the pressure of the gas. 



GAS BURNER OF HIGH PRESSURE (Fig. 5889, page 1073). 



This burner is employed when the pressure is more than 25 millimetres of water. It has one or two jets. 

 The figure represents the flame full size, the supports only being slightly reduced. 



A. Large yellow flame of low illuminating power. 



B. Luminous part, very -intense. It is on this that the saccharimeter is directed. It is only to be obtained by Laurent's 



burners and lamps, 

 c. Chimney. 



The flame is composed of two parts, the one H, violet, high, large and very hot, the other D, a cone not so hot ; it is 



blue in the gas burners and violet in the spirit lamp. 

 The spoon consists of a platinum gauze cup G soldered to a strong platinum wire F, which is fixed in the corner at 



the base of the chimney by means of a pin p and retained by a chain. It is easily replaced. 



The salt is placed in the cup G ; when it melts it ascends by capillarity to t!he edge, which is very hot, and gives in 

 the prolongation in B a narrow flame excessively brilliant, and of which the instrument only utilises a small circle 

 of 2 millimetres in diameter. It is better to feed the flame frequently and with small fragments of fused salt, for 

 if there is too much or too little, the intensely luminous flame B is not obtained with the same completeness. It 

 is essential to obtain this brilliant light B, and the shape of the flame depends on the position of the spoon. 

 In burners of high pressure and in the spirit lamp the flame does not require regulating. In the burner of low tempera- 

 ture it is necessary to regulate by the collar v. 



The edge of the spoon should be placed 15 millimetres above the tube T. This is necessary, because it is often attempted 

 to bring the spoon into the centre of the flame, to obtain more light ; if the spoon is out of order it can be drawn to the side 

 while the gas is burning, and raised or lowered, or advanced more or less. When in its right place the brilliant interior flame B 

 is perceived. 



With this arrangement there is no risk of the fused salt falling into the tube x and obstructing the gas jet. 

 Should the spoon become coated with small spots they must be removed, as they cause irregularity in the flame, and if a 

 whitish deposit appears the spoon is taken out and washed. 



The tube T is 13 millimetres in diameter. It has no collar to close the air holes, and is suited for all pressures down to 25 milli- 

 metres. Its lowest limit is reached when it begins to burn inside the tubes. The stronger the pressure the more intense is the 

 light and the steadier the flame. With a pressure of from 30 to 40 millimetres, for example, and two jets, the light is quite sufficient 

 for all purposes. 



In order to light the burner the air holes are closed with two fingers, and the light applied from above. 

 The column of the burner is not fixed in the socket, so that it is possible to employ two systems of burners and to bring them 

 near enough for the chimney to touch ; four flames are thus obtained when a more intense light is required. 



BURNER OF LOW PRESSURE. 



This burner is employed when the gas pressure is under 25 millimetres of water. 



It is similar to the last, but the light is neither so intense nor so steady It is possible, however, to do work with it, but the 

 spirit lamp (eolipyle) is preferable. 



SPIRIT LAMP (Fig. 5898). 



This lamp gives an intensely yellow flame and in every way takes the place of the gas lamp, especially when the pressure is 

 I less than 25 millimetres (i in.) of water. Methylated spirit or wood spirit may be used. 

 L. Lamp to heat boiler H, fed with spirit. 

 A. Screw with washer into which wick is inserted. 

 A. Screw with washer, screwed loosely on A. It serves to regulate the flame ; in working it is unscrewed by two or three 



turns. 



N. Strong frame containing lamp L and supporting boiler H. 

 H. Boiler of copper, containing the spirit. It is hard soldered to the support N. 

 TT. Forked tube-screwed on to I and carrying the two chimneys cc. 

 cc. Chimneys bearing two platinum spoons GO, and terminated at their lower end by two small tubes soft soldered into 



tube TT. They can be put aside in the case, for example, of adapting two spirit lamps. 

 GO. Spoons fixed by means of pegs or pins at the corners ; they are easily replaced. 

 v. Collar for opening or shutting the air holes. 



VALVE. 



E. Screw with washer, bearing the valve s and screwed into the cone F. 

 p. Ring of lead forming joint. 

 s. Valve, 

 j. Stem of valve. 

 R. Spring to close the valve s. 



TO PREPARE THE LAMP FOR USE. 



Unscrew A and withdraw the wick, introduce a small funnel with the wick inside, and pour spirit slowly until the lamp is 

 nearly full. Replace the saturated wick in A, and rescrew it on the lamp. Unscrew D 2 or 3 millimetres, and pass the wick through 

 lit about 4 millimetres. 



There is a small hole in the upper part of the lamp for the admission of the air required to replace the spirit as it is consumed, 

 |and it is necessary to see that it is not stopped up. 



'In CHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



