A Simple Automatic Water Still H. B. GORDON,Alabama Polytechnic Institute, Auburn, Ala.
I
T OFTEN happens that a worker in a small laboratory feels that he can hardly afford to purchase an automatic still of the usual type, yet the need for distilled water is imperative and the use of a still which is not automatic consumes more time than is justified. The simple, inexpensive still shown in the accompanying sketch should prove helpful in a small laboratory, or in a larger laboratory when the large still is out of order. This still may be made from a 500-ml. distillation flask by sealing two additional side tubes near the bottom of the flask, as shown in the sketch. I n operation the set-up of the still is essentially as indicated. The water from the condenser, A , flows into a small water bath, B, the overflow from which is connected with the sink. A siphon, C, is connected with the second side tube of the still, D,and serves to keep the water in the bath and the still, E , a t approximately the same level. As distillation progresses some water must be drawn from the still to prevent excessive concentration of dissolved material. For this purpose a third side tube, F , is provided. If no temporary hardness is present the tip of F may be drawn down to a jet of such size as to permit the outflow of water a t the rate desired. I n the presence of temporary hardness the outflow may better be regulated by means of a rubber tube and screw-cock as shown. This avoids clogging of the glass jet by precipitated solids and permits flushing to remove solids by merely loosening the cock. An air trap, G, should be used to prevent air dissolved in the feed water from collecting in the siphon and interrupting its action. A considerable increase in efficiency of operation results from the use of the preheater, H . This may be made of 10mm. copper tubing, coiled as shown around the top of the
burner. Care must be taken that all parts of this coil slope upward toward the still, so that the heated water (and steam) will rise to the still instead of tending to move in the opposite direction. Of course the efficiency of the still may be further increased by wrapping the flask with asbestos paper.
H \
-AUTOMATIC WATERSTILL
To secure smooth boiling, scraps of porous porcelain or boiling tubes may be used. The former are to be preferred if either side tube D or F is attached very near the bottom of the flask, since in this case the boiling liquid tends to throw the light boiling tubes into the opening of the side tube. RECEIVED June 21, 1933.
An Adjustable Temperature Regulator W. GEORGEPARKS,~ Department of Chemistry, Columbia University, New York, N. Y.
A
BIMPLE adjustable temperature regulator which has and water was used; a t the other temperatures pure water) was been very successful in this laboratory for the past cooled by circulating calcium chloride brine through cooling two years is shown in Figure 1. This regulator can be coils arranged around the sides of the bath. Slightly more constructed readily from the common type of cooling than necessary was employed so that the regulator which accompanies any Freas thermostat. desired temperature could be maintained by reguIt consists of a large mercury reservoir A with a lating the heat supplied by electric heater units. side tube B of uniform bore. The side tube is fitted The brine was maintained a t a temperature of apwith a brass cap through which is threaded a nickel proximately - 15" C. in an insulated tank by a large rod carrying a tight-fitting rubber plunger. The Frigidaire compressor and evaporator. The brine b r a s s c a p is c e m e n t e d to the side t u b e w i t h was circulated by a pump and the quantity needed de Khotinsky medium cement. By raising or lowerfor the various temperatures controlled by suitable ing this plunger the height of the mercury a t C can valves, which were so a r r a n g e d t h a t a varying be varied a t will. This device, which eliminates number of cooling coils could be used in the bath. the necessity of adding or removing mercury from For operating the thermostat successfully below the regulator every time the temperature is changed, room temperature, both caps of the regulator must is of particular value in the determination of the be tightly sealed with paraffin to prevent condensatemperature coefficients of galvanic cells. In this tion of moisture within the side arm and a t the connection this regulator has been used from 0" to mercury contact surface a t C. The regulator was 30' C. a t 10" intervals. The desired temperature used in conjunction with a relay switch, such as was maintained to *0.02" C. A larger temperadescribed by Beaver and Beaver2 with very satisture range is possible if desired. factory results. The thermostat liquid (at 0" a mixture of alcohol I E * RECEIVED July 14, 1933. 1 Present address, Rhode Island State College, Kingston, TEMPERATURE -REGULATOR R. I. * Beaver and Beaver, IND. ENQ.C H ~ M15, . , 359 (1923). 357
