V O L U M E 2 7 , NO, 2, F E B R U A R Y 1 9 5 5 tion of the balance, a system which would not interfere with the h l a n c e properties of the beam itself. OPTICALLY-CONTROLLED COLLECTOR
I n the second collector the same type of siphon was employed. Instead of using the weight of the solvent and the movement of :t balance arm to initiate the action, the siphon was fixed in a position so that the delivery arm interrupted a light beam impinging on a phototube. Because the siphon is fixed, provision can be made to minimize evaporation of the solvent by the technique of Mader and Mader ( 7 )or under more serious conditions by the use of refrigeration coils. When the siphon delivers, and solvent passes through the delivery tuhe, more light is transmitted onto the phototube. This effect, suitably amplified, energizes a solenoid-ratchet device to turn the table (Figure 2). Intensification of the light which falls on the phototube, V-4, makes the control grid of VO more negative. This causes the potential a t b and correspondingly at d to become more positive, permitting a fiow of current through one half of the 5692 h b e . 7’3, to close the L3fS relay, L1. With the relay closed, grid f of the other half of the 5692 tube is now connected to the positive power supply and current flows through the tube to close relay LOand consequently energize the electromagnet, S . The electromagnet is maintained in this condition as long as liquid is passing t,hrough the delivery arm of the siphon and for an additional time (to alloiv complete drainage of the solvent) determined by the R-C con&nt,s of the syst,em, Cs, C,, GI,, Rls.Iflr, and PO, through which the grid is grounded. The time delay can be varied by adjustment of PO. Final release of the electromagnet causes a spring-driven mechanism similar to that described by Schram and Bigwood (8) t,o rotate the table to its nest position. Pl is adjusted by trial and error with the siphon in posit,ion, so that the presence or absence of solvent, will determine the opening and closing of relay L,. The circuit described is essentially that of Johnson ( 5 ) . I t has been modified by the addition of the 6SLiGT tube, VI, n i t h its own separately biased grid potential as a “caseode” amplifier (3), t o provide a constant load for the 12SHi tube with a result,ant increase in gain and stability. The system works very well in this case, where the relays must he operated by small differences iri light intensity relative to the light levels used. It was not necessary to change the settings during 6 months when the collector \vas in nearly constant operation. ACKh-OWLEDGXIENT
The expense of this investigation was covered by a grant from The Helen Hay Whitney Foundation, which is gratefully acknoivledged. LITERATURE CITED
Brimley, 11. C . , and Snow, -\. J., J . Sci.Iustr., 26, 73 (1949). (2) Chapon, L., Bztll. SOC. chim.,1952, 53s.
(1)
Gray, J. W.,“Direct-Coupled ;iniplifiers.” in “Vacuum Tube .%niplifiers,” Vol. IS, Radiation Laboratory Series, L. S . Ridenour, ed., p. 439, RIcGraw-Hill Book Co.. Kew York, 1948. ( 4 ) James, d.T., Martin, A . J. P., and Randall, S. S., Biochem. J . , 49, (3)
293 (1951).
Johnson, Marvin, University of Wisconsin. private communication. (6) l l a d e r . C., and l l a d e r , G., ASAL.CHEIZ..25, 1423 (1953). ( i )Ihid.,p. 1556. (8) Schrain, Eric, and Bigwood, E. J., Ihid.,25, 1424 (1953). (5)
Fermentation of Sugars by an Ultramicrotechnique Prior to Paper Chromatography Kenneth T. Williams and Arthur Bevenue, Western Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture, Albany 6, Calif.
authors, continuing work on the unfermentable sugars in T”” vegetahles [Killiams, K. T., Potter, E. F., and Bevenue, A ,
J . Assoc. O#c. Agr. Chemists, 35, 484 (1952)], have developed a technique for fermenting very small volumes of sugar solutions
331 with commercial baker’s yeast. h recent article liy Porter and Hoban on enzymatic hydrolysis [Porter, W. L., and Hoban, Xancy, ASAL. CHEJI.,26, 1846 (1954)] has prompted a description of the procedure as a further supplement to ult,ramierotechniques for paper chromatography.
h melting point t,uhe (1+ mm. by 100 mm.) was heated a t the center and drawn into two test tubes Jvith a head formed on the bottom of each tube. Medicine droppers were modified t)y drawing the tips to a capil!ary to fit easily into the micro test tubes. Holes a b o u t 2 mm. in diameter were drilled into wooden or metal hlocks to support the test tubes in an upright position. Small stirrers were made from draxvn glass rod. Three milliliters of acetate buffer and 8 ml. of 0.2M potassium tlihydrogen phosphate were included in 100 nil. of a 10% washtxd baker’s yeast suspension [Wi!liams, I
