Dec., 1918
T H E J O U R N A L O F I X D U S T R I A L ALVD E N G I N E E R I N G C H E M I S T R Y
A NEW ILLUMINATOR FOR MICROSCOPES1 SECOND PAPER By ALEXANDER SILVERXAN Received September 25, 1918
Since t h e publication of t h e first paper2 a b o u t one year ago, a number of i m p o r t a n t improvements have been made in t h e illuminator3 for microscopes therein described.
FIG 1
I n t h e first paper t h e l a m p holder was attached t o t h e t u b e of t h e microscope b y a clamp. I n t h e newer form (Fig. I) three fingers fasten t h e holder directly t o t h e objective (Fig. 2 ) . T h e fingers are iris-like in operation a n d are controlled b y springs, so t h a t it is possible t o attach t h e illuminator t o a n y objective. T h e l a m p described in t h e earlier paper was a 6 volt, 0 . 7 ampere unit operated b y dry or storage cells. T h e new l a m p is a 9 volt, 0 . 7 ampere unit of blue (daylight) glass a n d gives about 50 per cent more light. A rheostat has been devised which screws into a n ordinary lighting socket. T h e rheostat has three taps, 1 0 7 volt, 1 1 2 volt, a n d 1 1 8 volt. A rheostat for 2 2 0 volt circuits is in preparation. If a greater light intensity is desired one can connect with a lower voltage t a p . This is of a d v a n t a g e in photography. T h e normal voltage connection suffices for visual m-ork. Recent experiments with a colorless, one ampere, 13 volt l a m p show t h a t it can be employed safely. T h e l a m p was placed i n t h e holder, clamped t o various objectives, a n d allowed t o r u n continuously for half a n hour, a period of t i m e far exceeding a n y employed in actual operation. T h e objectives were not affected although t h e l a m p carried a n overvoltage of 1 5 per cent. Further, a colorless 0 . 7 ampere, 20 volt lamp was silvered instead of enameled. T h e silvered reflect o r reduces t h e a m o u n t of heat radiated towards t h e objective. Blackening t h e outer surface of t h e reflec1 Presented a t the Cleveland Meeting of the American Chemical Society, September 11, 1918. THISJOURNAL,9 (1917), 971. U. S . Pat. 1,267,287. Can. P a t . 185,283. Other U. S. and foreign patents pending
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t o r also reduces t h e heat traveling towards t h e objective. Both lamps yielded a light of much greater intensity t h a n a n y hitherto employed. Results obtained will be discussed later. T h e lamp reflector is placed a t a n angle of 4 j 0 t o t h e plane surface of t h e stage. Low power objectives may be a n inch or more above t h e stage, so a tube has been designed which m a y be clamped t o t h e stage. T h e lower end of t h e tube will support t h e lamp a t a constant distance from t h e object under examination a n d t h e objective m a y be raised or lowered inside t h e tube. T h e inner surface of t h e tube is dull black. il shutter m a y a t times prove desirable t o cut t h e light off from one-half of t h e circular source. T h e experimental shutter employed for this purpose is a dull black disk which covers half of t h e lamp a n d is attached b y prongs which are held b y t h e lamp. DetaiIs are sometimes visible b y this method which are obscured when t h e entire l a m p is bare. T h e illuminator m a y be attached t o a microscope together with a vertical illuminator, t h u s affording a comparison of t h e separate effects of oblique a n d vertical light on a n object. There is a marked difference in t h e appearance of metallurgical specimens under t h e t w o illuminators, t h e new one facilitating t h e s t u d y of depressions a n d showing details not hitherto revealed. I n blow-holes a n d pits t h e slag content, etc., may be seen. T h e pits appear black b y vertical light.
FIG.2
When paper, textiles, insulating materials, biological specimens, etc., with light-absorbing surfaces, are examined b y vertical light, little or none of t h e structure is visible. Under t h e new l a m p a wealth of detail is seen which astonishes t h e observer who employs t h e device for t h e first time. Should one wish t o employ t h e new illuminator alone, a n d remove t h e vertical illuminator, it is necessary t o
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cxtend t h e draw-tube of the microscope t o about t h e 176 mm. point for clear images, as most microscopes a t present on t h e market arc correctcd for t h e normally interposed vertical illuminator. Questions have arisen repeatedly regardinE the use of a lamp of such low wattngc for photomicrography. Experiments conducted in the writer's laboratory prove t h a t good rcsults are obtainable with t h e 0.7 ampere, 9 volt daylight lamp with S and 16 mm. objectives and those of lower power, when the eyepiece is removed. With t h e colorless 0.7 ampere, 20 volt siivered lamp or the one ampere. 1 3 volt lamp it is unnecessary t o remove t h e eyepiece, as the light intensity is ample t o yield clear images on t h e ground glass. Focusing may be facilitated by greasing the gronnd glass with a little vaseline, subsequently rubbing i t as dry as possihle with a cloth. Bronzes. highly poli:;hcd ball bearings, enamel, paper, etc., have heen photographcd in this way. The best results were obtained with Hammer Ortho extra fast and Hammer Ortho nonhalation plates. Figs. 3, 4, j, 6, 7 and 8 show results obtained with t h e 0.7 ampere, 20 volt silvered lamp with exposures of from 1 5 t o 30 seconds, using a 1 6 mm. objective and I O X eycpiecc. Fig. 3 is a blue enameled steel; 4, a steel casting, 0.37 carbon, not pressed or heat treated; j, an iron-zinc alloy obtained in zinc manufacture; 6. a picce of blue cover paper; 7, a piecc of cloth; R, a cast iron specimen.
I n conclusion, the writer wishes t o express his appreciation t o the scicntists in various fields who have experimented with the new device and made suggestions which have resulted in valuable improvements in methods of application. :CHOOL
CHerrsmu or P I i i S U U P C i l
OP
UNIYIRSLTV
P I T I S B V B O B , PA.
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A SPECIAL STOPCOCK FOR DROPPING LIOUIDS ARRANGED FOR E Q U A L I Z I N G 'riiE ABOVE AND BELOW THE OUTLET IN THE STOPCOCK'
PRESSURE
By IIa~rtvI,.. Plsrrsn Received June 4, 1918.
T h e stopcock described herein was disigned in connection with a generator for carbon dioxide which was t o be us-d alternately with prcssures helow and ahovz atmospheric in the final preparation of cupric ovidz and for the det-rmination of nitrogen by the Dumas method according to t h e modification of Fieldner and Taylor.2 Ordinarily an outside tube connecting the top of the reservoir of acid with the upper part of the container of the carbonate is used. I n this new apparatus the connection is made by means of an annular groove in t h e key of t h e stopcock so t h a t no matter which position the key occupies there is always communica8 Presemted at the Boston Meeting oi the American Chemical Society, September 10-13. 1917. Pieldner and Taylor. Tnra Joaas~r, 7 (1915). 106.
