For determining the specific rotation of optically active substances.A Borosilicate glass tube (size 200 mm) is enclosed in a circular aluminium tube with top door for access and exclusion of external light. The circular scale is attached near to analyzer and a range of measurement is 0 - 360'.Vernier moveable on the scale enables reading of optical rotation to 60 seconds. Rough and fine adjustment, provided giving three parts field for easy setting adjustable half shadow angles. The instrument can be used on monochromatic light. The emerging light is then observed through a rotatable polarized lens analyser which is used as eye piece. The angle of light is rotated and read directly of the circular scale. Supplied on the adjustable stand, packed in cardboard box. fitted with Bi-Quartz in place of mica, giving coloured distinction, accuracy + 5'