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BAIRD &TXTLOCK (LONDON) LTD. 



LAURENT'S SACCHARIMETER FOR THE ORDINARY WHITE LIGHT. 



The polariscopc just described is constructed for use with yellow sodium light. It is a general apparatus, and serves for all 

 rotatory substances, and it is recommended for research laboratories, scientific establishments, etc., notwithstanding the trouble 

 which the production of the sodium flame occasions. 



But for industrial purposes, as in the case of refineries where sugar is the principal substance, and where speed is a desideratum, 

 the employment of an ordinary white light is preferable, as it is always at hand. 



In order to arrive at this object, there is interposed between the scale c and the analyser OH of the polariscope already described 

 a Soleil compensator (a quartz wedge). This is shown in Fig. 3. The lens N, the screw F, and the analyser OH (placed behind the 

 compensator) are of the same construction as in the other instrument. The scale c is replaced by a disc which acts as a screen 

 (c in diagram). The rest of the instrument is like Fig. 3, except that in place of the gas burner any white flame may be employed 

 which is placed 20 centimetres from the lens n. 



The app-arance seen in the instrument is one of light and shade, and there is no sensible colour visible, as in the old Solei. 

 sacchanmt-. It is possible by means of the lever u to obtain more or less light as is required. A flat flame of gas or of petroleuir 

 employed in the direction of its length is much more intense than a rounded jet. 



The manipulation of this instrument is almost the same as described for the grand model. The circular divisions of the dia 

 c and the index, Fig. 3, are replaced by the rectilineal di\ isions of the scale R, and of the vernier v. In order to adjust the apparatus 

 to zero the zeros of the vernier and scale are made to coincide, and if this does not produce uniformity of shade, the screw F i; 

 'urned one way or the other until the field is neutral. 



If the liquid to be measured gives a rotation above, for example, 60 degrees, it may be a little more exact to regulate the 

 apparatus, not to zero, but to the 100, with a standard quartz plate. This is placed in the apparatus, the zero of the vernier \ 

 brought on to the division corresponding to the exact value of the plate, and the uniformity of shades established by the screw F, 



When white light is used it is necessary to leave the bichromate crystal E, Fig. 3, in the apparatus. 

 To bring the apparatus to the primitive state of the polariscope (with sodium flame), draw out the compensator (a pin deter- 

 mines its position), replace N, F, and OH to their first position (Fig. 4), then place the zero of the vernier opposite the zero o: 

 the dial, and establish the uniformity of shades by looking into o and by turning F. 



A description of this new apparatus was presented to the Academy of Sciences by N. Cornu in February, 1882, and to the 

 Societe francaise de Physique by M. Dufet in May, 1882. 



5908 



5907 Apparatus for extracting the cane sugar from beet sugar for polarisation, as described in 

 J.S.C.I., p. 753, July, 1901, and by A. Hergfeld, Zeits, Vereins Deutsch Zuckerind 1001 

 (543), 334-335 ' each 12 



Extra Flasks 



5908 s 



Educational Set of Polarising Apparatus, complete in polished wood case, comprising 

 analysing bundle, rotating Nicol prism on stand. Objects : Benzoic acid, section of 

 quill, gypsum even tint showing complementary colours, ditto mica, selenite' wedge and 

 selenite design, also three uniaxial and biaxial crystals in brass cells, demonstrating the 

 rings surrounding the optic axes. The whole packed with full instructions for use 



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1 10 ( 



1078 



