An apparatus for viewing varying thicknesses of a solution with a direct-vision spectroscope.

THE principle of altering the thickness of a solution during spectroscopic examination is of course an old one, but the writer has not seen a published account of a simple and inexpensive apparatus. That described below can easily be made in the laboratory for a few shillings, and requires little skill mechanically or in glass-blowing. It has the great advantage that 5 ml. of solution can be examined in a layer 5 in. thick. The apparatus The four essential parts are a cup, a plunger, a spectroscope above and a light source below. The spectroscope S and plunger P are mounted by means of bark corks in a long glass sleeve (A, in Fig. 1). The majority of spectroscopes will fit into the sleeve ofthe dimensions suggested, but should an unusually wide spectroscope have to be mounted, it is an easy matter to alter the dimensions ofthe mounting parts accordingly. bne of the attractions of the apparatus is that a spectroscope already in one's possession can be utilized. The glass sleeve A slides comfortably over 10 a second B which carries the cup C. The source of light L is a small frosted' C electric bulb run from the mains supply-a B 25 W. standard tubular lamp of appropriate a voltage is suitable-but in the absence of a 11 C L mains supply a motor-car tubular lamp and a battery could be used. The lamp-socket is l fixed on a baseboard and connected by the usual flex and plug. A wooden housing H is divided into two parts by a diaphragm D. The lower part of the housing covers the lamp, is supplied with ample~ vetlto hoe an fit sngyit Fig. 1. Apparatus for spectroscopicex ample en i ation les d s snugly into amination of varying thicknesses of a the baseboard. The upper part of the housing solution. acts as a sleeve in which slides the plungerglass-sleeve A. The lower cork fixing the bottom of the cup into its glass-sleeve B rests on the diaphragm D, which is countersunk to receive it, and has a central hole to allow the light to pass.