For the examination of liquids open the prism box and place a few drops upon the ground surface of the lower prism. Close and fasten the prism box when the liquid will be squeezed into a thin film between the prism. Focus the crosswire with the eyepiece, adjust the mirror until the illumination is good, and gently turn the prism box by means of a milled head screw forwards and backwards until a coloured band appears in he field of view. By turning the milled ring at the base of the telescope, a position will be found at which the coloured band will be eliminated, the field of view being partly light and partly dark with a sharp dividing line. Bring this sharp dividing line into coincidence with the intersection of the crosswires and read the refractive index or sugar percentage on the divided arc by means of the magnifier.

The scale is divided to the third decimal place, the fourth being easily oriented by estimation. It will be noted that the hing of the prism box is so constructed that the lower prism in the box may be removed. For the examination of plastic bodies such as resin, remove the lower prism box, soften the material by heat, and smear a little on the exposed surface of the upper prism, then proced as above. To examine crystals or glasses. A specimen should be prepared, similar in shape to the standard glass test piece provided. Moisten the polished surface of the specimen with the smallest possible quantity of monobromonapthalene and place it upon the suface of the prism with the ground edge directed towards the mirror. Care must be taken to avoid excess of monobromonathalne as this may spoil the definition and confuse the reading. When the correct quantity is used, the specimen will adhere firmly to the prism face.The instrument is sent out carefully adjusted, but it is as well to verify the setting by applying the class test piece to the prism and nothing if the reading is that marked on the piece. I this is not the case, adjust the small squared screw at the back of the telescope with the key provided until agreement is secured. The mean of several reading should be taken if great accuracy is desired.

An ideal instrument for quality control with better accuracy. Suitable for testing sugar solution and other optically active liquids. Accommodate 220 mm. length tube. The polarimeter consists basically of two polarizing elements of 'Polaroid' one of which is fixed, the other capable of rotation and mounted within a graduated scale in order to measure its orientation with respect to the other. When the planes of polarisation of the two elements are mutually perpendicular no light is transmitted through the system. A thin plate of quartz is positioned to cover half the aperture of one of the elements in order to introduce a 'half shadow effect'. The effects to cause an extinction of light in one half of the field a few degrees normally 7 degrees, before the other half of the field reaches its extinction position. Thus a balance can be achieved where one half of the field is reducing in intensity as the other half is increasing, as the scale is rotated. The position of the scale at which the two halves are of equal intensity is the balance position and is used in all determinations. On introducing an optically active sample between the polarizing elements the balance is disturbed and it is necessary to rebalance by turning the scale. The amount by which the scale is moved a direct measure of the sample optical activity.

An ideal instrument for quality control with better accuracy. Suitable for tesing sugar solution and oher optically active liquids. Accomodate 400 mm. length tube.The polarimeter consists basically of two polarising elements of 'Polaroid' one of which is fixed, the other capable of rotation and mounted within a graduated scale in order to measure its orientation with respect to the other. When the planes of polarisation of the two elements are mutually perpendicular no light is transmitted through the system. A thin plate of quartz is positioned to cover half the aperture of one of the elements in oder to introduce a 'half shadow effect'. The effectis to cause an extinction of light in one half of the field a few degrees normally 7 degrees, before the other half of the field reaches its extinction position. Thus a balance can be achieved where one half of the field is reducing in intensity as the other half is increasing, as the scale is rotated. The position of the scale at which the two halves are of equal intensity is the balance position and is used in all determinations. On introducing an optically active sample between the polarising elements the balance is disturbed and it is necesary to rebalance by turning the scale. The amount by which the scale is moved a direct measure of the sample optical activity.