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amined b y chemists, biologists a n d metallographers a n d pronounced satisfactory for both direct observation a n d microphotography, i t is described here for those who may be interested. A s shown in t h e accompanying illustration, a small circular tube-lamp surrounds t h e objective a n d is attached t o a holder which is clamped t o t h e microscope tube. T h e design of both clamp a n d holder may be modified t o fit a binocular microscope. For t h e present, t h e holder illustrated is used because of t h e variation i n diameter and shape of objectives. T h e lamp shown is a 6-volt tungsten lamp operated b y six d r y cells. Modffications of t h e l a m p are possible. T h e present one might be replaced b y a nitrogenfilled tungsten, daylight tungsten, mercury or carbon dioxide lamp. T h e advantages i n t h e use of. t h e new device lie in t h e fact t h a t a n object is illuminated b y a circular source of light, so directed b y t h e reflector on t h e upper wall of t h e t u b e t h a t diffusion results. F u r t h e r , t h e light is always in place a n d is raised a n d lowered with t h e microscope t u b e , t h u s obviating t h e necessity for readjustment experienced in using vertical illuminators. T h e lamp, fitting snugly about t h e objective, enables one t o lower t h e light into hollow objects too deep t o permit of t h e use of a vertical illuminator. I n microphotography the lamp has been used t o good advantage. Satisfactory results have been obtained on specimens with a 5 m m . eyepiece a n d 8 , 16 a n d 3 2 m m . objectives. It has heretofore been quite difficult t o obtain good photographs in metallography with low-power objectives using older forms of illuminators. With t h e new illuminator excellent results were obtained. T h e time of exposure was, on a n average, 6 minutes for t h e 8. mm., 2'/2 minutes for t h e 16 mm., a n d I ' / ~minutes for t h e 3 2 m m . objective.
intake
B-3-way
stop cock as !n standard
OF P I T T S B U R G H PITTSBURGH. PA.
A NEW MODEL OF THE BURRELL AND OBERFELL APPARATUS FOR THE ANALYSIS OF ILLUMINATING GAS R . S U Y D A M , JR.
Received May 21, 1917
T h e a p p a r a t u s shown herewith is practically identical with t h e apparatus described b y Burrell a n d Oberfell in THIS J O U R N A L for March, 1916, page 2 2 8 , except t h a t i t has been p u t in a more compact s t a n d which gives more protection t o t h e glass parts t h a n t h a t shown b y t h e above writers, a n d t h a t a silica t u b e has been substituted for t h e glass one used b y t h e m as a container for t h e copper oxide. T h e silica tube, which was made b y t h e Hanovia Chemical Company of Newark, N . J., was more t h a n paid for b y t h e saving of t h e expense for repairing t h e glass t u b e , which broke very frequently. T h e procedure for t h e analysis is identical with t h a t given b y Burrell a n d Oberfell. T h e apparatus has given excellent results a n d is recommended as being more satisfactory for t h e
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Orsat apparafus
stap cock a5 in Burrell and Oberfell apparatus for opening the rneasunng burette, either t o the , i - - -L --absorption pipettes or the compensator ,
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sed Silica Tube
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analysis of illuminating gas t h a n t h e s t a n d a r d forms of apparatus now on t h e market. DEPARTMENT OF C H E X I C A L
SCHOOL OF CHEMISTRY UNIVERSITY
B y J.
/,-Sample
Vol. 9, No.
ENGIKEERING
COLUMBIA UNIVERSITY, N E W YORK CITY
A USEFUL DISTILLING HEAD By ORLO STEARNS Received May 28, 1915
The accompanying drawing explains t h e constr uction of a useful distilling head. T h e angle between h a n d i should be about 110'. This head was specially designed for and found exceptionally efficient i n distilling troublesome fluid extracts. Such liquids often give rise t o a good deal of froth which carries some of t h e liquid along a n d renders redistillation necessary. Sometimes, however, t h e liquid is forced u p b y spurts, or again rises in a body passing into t h e a p p a r a t u s connected with t h e flask. I n t h e first instance t h e p a r t of t h e head t h a t does t h e most service is t h e lobes fJ' in which t h e bubbles readily break b y expansion a n d condensation. Bubbles often broke in passing t h e circular edge g,g' a t t h e lower end of t h e conical branch of t h e connecting t u b e , while t h e larger opening, across g,g', is less favorable for t h e entrance of bubbles t h a n a smaller one. T h e opening e in t h e lower p a r t of bulb is directly over t h e drainage hole c a n d t h e re-
OCt., I917
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in. on their flat surfaces. This is mounted on a piece of oak so t h a t it is securely fastened a t one end and free t o move at t h e other. When t h e temperature t o which it is subjected varies, the unequal expansion of t h e metals causes t h e free end t o move towards or away from a n adjustable contact point. If t h e entire current of t h e heating coils were passed through this thermostat, t h e contacts even of platinum would be fused b y t h e arcing of t h e current. Therefore only as much current as will pass through an incandescent lamp is relayed through the thermostat. This thermostat is bolted t o t h e top of t h e air b a t h inside b u t t h e screw which adjusts t h e temperature a t which t h e current is broken projects outside. T h e location of t h e thermostat is shown in dotted lines in t h e diagram. The current passing through t h e l a m p and thermostat actuates a magnet which breaks t h e heating current. This magnet and t h e interrupter which it operates, as well as t h e lamp and main switch, are mounted on top of t h e oven on a wooden board cut t o the size of the oven and having holes bored in i t t o accommodate the thermometer and ventilating holes. The magnet used b y the writer has 4 0 2 . of No. 26 double silkcovered copper wire wound on a 1;2-in. fiber t u b e with soft iron wire core. With a jo watt lamp in t h e
action produced when the liquid spurts has a tendency t o check or force back t h e ascending liquid. I n case t h e t u b e d becomes submerged, a small syphonic force is generated which tends t o e m p t y t h e bulb. It is possible t h a t this head may be adapted on a different scale for other similar purposes. Eimer a n d Amend will make this form of distilling head upon application. 4629 CARROLL ST. PITTSBURGH. PA.
AN ELECTRICALLY HEATED AND CONTROLLED AIR BATH
n-..
By WALTER P. SCHUCK
Received August 27, 1914
T h e writer recently installed electric heating and temperature control devices in a common air b a t h for use on 120-volt direct current. T h e details a n d results may be of interest t o others. The air b a t h was of the single-walled t y p e I O in. X I O in. X 1 2 in. T o conserve heat it was first covered with asbestos on all surfaces b y glueing t h e same on. T h e heating element consists of three coils of No. 28 “Climax” resistance wire, each coil containing 30 Et. and all connected in parallel. These coils are mounted on a piece of asbestos mill board 1/4 in. thick t h a t fits into t h e bottom of t h e air bath. Each coil is stretched three times across t h e width of t h e board so t h a t t h e terminals are a t binding posts on opposite sides. At t h e t w o other points t h e coil is laid around short stubs of slate pencil set into t h e board. For t h e control of temperature a thermostat was made b y soldering together a strip of zinc and copper each x7
socket this magnet operates t h e interrupter quickly and holds it well. If other voltages or different sized lamps were used the ampere turns of the magnet could of course be adjusted t o suit. The interrupter is a piece of spring brass about 9 in. long and one-half in. wide which is securely fastened into a post a t one end and a t such a height t h a t it is opposite the core of the magnet. The armature is soldered on this strip of brass and is of soft iron one-half in. square and in. thick. At t h e free end of the interrupter is the plati n u m contact‘ t h a t makes and breaks t h e heating current. T h e brass strip is bent so t h a t normally it would keep t h e contacts about I in. apart, but as this throws t h e armature too far from t h e magnet, a peg is set into t h e board in such position t h a t it keeps the strip from pulling t h e contacts more t h a n 3/!16 in. apart. I t is also necessary t o p u t a piece of cardboard I m m . thick between the armature and t h e
