BAIRD &TATLOCK (LONDON) LTD. 



BOILER. 

 Loosen the screw E which carries the valve s, in order to make sure that the latter is working well, and that the spring is 



The rod j should be centred in its hole, but if it is not so exactly it is essential that it returns quickly to its place when acted 

 on in any direction. 



The boiler attached to the apparatus should be filled to within 5 millimetres of the edge by means of the funnel, and care 

 taken to rescrew E firmly to avoid any leakage. 



The tube T is unscrewed, and to make sure that the hole in the cone placed within I is quite clear, a needle or pm is inserted 

 4 or 5 millimetres. 



Tie adjustments o/ the valve s and of the small hole i are important, and ensure the proper working of the apparatus. 



CHIMNEYS AND SPOONS. 



The chimneys cc and spoons GG are properly placed so as to give the intense inner flame B, and the two flames are arranged 

 one behind the other in the axis of the saccharimeter. 



It is necessary to replace the salt more frequently in the spoon than when using the gas burner. 



MANIPULATION OF THE LAMP. 



The screw E being firm, the tube T and the chimneys in their places, the operator should close the collar and light the lamp 

 L, and wait about three minutes. It is better to wait than to draw the wick out more than 4 millimetres. 



When the sound of escaping vapour is heard the two extremities TT are lit, and the air holes opened. If it is too soon the 

 flames will burn in the tubes, and if this happens they should be extinguished for a while. If the pressure in the boiler H is sufficient 

 the flame will burn at TT with a small violet interior cone D (Fig. i). At first the cone is rather low and unsteady, but it soon gives 

 an intensely yellow flame. It occasionally happens that the lamp gives too little light and tends to burn inside the tube, or too 

 much light, and appears to rise up and quit the tubes. In either case the flame can be regulated by the screw D ; by screwing 

 tighter it increases, and by unscrewing, it reduces the flame. Generally it is unnecessary to touch it when the wick is drawn 

 through 4 or 5 millimetres. 



Finally, when the spirit in the boiler is nearly burnt the two flames assume a particular form. The interior cone disappears 

 and the flame lengthens, the bubbling in the boiler also ceases. The lamp should then be withdrawn and extinguished. The measure 

 cf spirit introduced into the boiler lasts about twenty-five minutes. It is as well to use a measure when filling the boiler so as to 

 avoid pouring too much in. 



When alcohol is employed the collar should be raised so as to give a full supply of air, but with wood spirit it should be lowered. 



If anything abnormal is observed the lamp should be at once withdrawn. 



The base of the pedestal N is cut on one side in view of the possible employment of two lamps in order to obtain when neces- 

 sary a still more brilliant light. They are supported in such a manner that the four chimneys touch as well as the cut side. The 

 position of the two chimneys of the second lamp is changed in order that the four flames may be in the same prolongation and 

 in the axis of the saccharimeter. 



The centre of the flame ought to be 20 centimetres from the lens B of the polariser. 



DESCRIPTION OF APPARATUS (Fig. 5888). 



The illustration represents the grand model set up ready for use, as seen from the side. 



A. Yellow monochromatic jets, placed 20 centimetres from B. 



B. Lens, screwed on the tube I. 



i. Bronzed tube carrying lens B and screwed on to E. 



E. Barrel, carrying a diaphragm with small hole, which receives a cap containing a crystal of potassium bichromate, the 



object of which is to act as a ray filter and to render the flame more nearly approaching monochromatic light. 



When the liquids are yellow (but clear) the bichromate crystal is not used. It is only inserted when the liquids are colourless. 

 R. Tube carrying the lever K, it enters into p, and bears a tube containing the polariser, and a lens which can be unscrewed. 

 p. Tube fixed on the body of the instrument L. 



D. Diaphragm, one-half of which is covered by a plate of quartz, which is in a line with the telescope OH. 

 K. Lever fixed on polarising tube R, and rendered movable by the crank j. 

 j. Crank fixed on the shaft x. 

 x. Shaft carrying the crank j and the lever u. 

 U. Lever fixed on x to turn the polariser by means of j and K, and in order to give more or less light. 



If the liquid is little coloured, the lever is raised as far as the stop. If it is coloured, it is lowered more or less. 



Body of apparatus in bronze, V-shaped, 60 centimetres long, planed and dressed, 

 c. Disc carrying the divisions and the index. 



M. Mirror, throwing the light from the burners on to the divisions, and obviating the employment of an auxiliary light. 

 N. Lens for reading the divisions of the scale. 

 H. Eyepiece, placed in tube which carries the index. It possesses an angular movement. 



F. Regulating screw, to establish uniformity of shades, when the zero of the vernier coincides with that of the coriesponding 



division. It pushes the tube H, which a strong counter spring brings back. 

 o. Cap of eyepiece, movable in H. 



MANIPULATION OF GRAND MODEL. 



The lever u being raised to its stop and the screw Q pressed firmly, the apparatus is directed towards the flame A. 



The observer looks through the lens N and adjusts its focus, the mirror throwing the required light on the divisions. On 

 looking through the eyepiece, and turning the screw G, the appearance a or c of Fig. 5897 is seen, that is, a disc divided into two, 

 one-half clearyellow, the other half dark yellow, and the tube o is pushed in or out to see their separation clearly. This point is 

 very important, in order to establish later the uniformity of shades. The better it is done the more sensitive is the apparatus. There 

 should be no perceptible line of division between the two halves of the disc. 



CROSS STREET HATTOTST GARDETST, E-C 



