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receptacles, are very easily sterilized and have given excellent results in practice. Every effort should be made t o keep all materials covered t o prevent the entrance of these organisms from t h c air.
m-ater stored in thc bottling plants should be kept in the dark. We wish t o suggest to bottlers that they discard aooden kegs as they have been found to be carriers of yeasts and undesirable bacteria even after attempts have becn made to sterilize them with hot water. Salt-glaecil pottery, where substituted for aooden
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GHE.1IISTRY
,I*CIEK,UL"CIC'IL
1.nean.\ruxits KASSAS
L~NIYZRSITY OF
LAWXEYCE
I
LABORATORY AND PLANT
A lecture given by 1)r. C. E. Kenneth Mees on the " S a t u r e of Color" before the Rochester section of Rrccked X a y 3 , 1913 the American Clicmical Society suggested these simThe development of projection apparat.us within ple experiments. for in that address Dr. Mees used t h e the last few years, producing forms with which work Zeiss complementary color projection apparatus, the of precision can be done, naturally led to the use principles of which are used in the instrument I have of such instruments in fields whcre projection hereto- here. IIowwer, the Zciss instrument is too difficult t o fore has not entered. The mention of projection apparatus recalls to the minds of most people simply the set up and has othcr objections which made a simprocess of projecting lantern slides, hut the physicist plification very desirable for our purposes. Mr. W. L. has for a long while used projection in lecture experi- Patterson, of the Bausch & Lomb Optical Co., therements and laboratory work. Of late the. biologist fore undertook the construction of a complementary has found i t most useful for lantern slides, opaque ob- color apparatus which would have the form of a conSOME PROJECTION EXPERIMENTS WITH SPECTRA' BY 11.
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jeers, and for microscopical projection, not to replace the table microscope but as an accessory I t has always seemed to me that the chemist could use projection (more especially in lectures) profitably and t o a large extent if he would hut worlc out a few experiments as a beginning, and add to them as his familiarity with the projection suggests othcr esperiments. The first of these chemical experiments with the aid of projection were given by Dr. Frank B. Kenrick, of the University of Toronto, and m w l f , a t the gcnera.1 meeting of this Society at the Washington mceting, and the fern experiments I now havc t o offer are more in the line of physics but havc a n application to the teaching of chemistry especially in qualitative analysis n-here the spectroscope is used for the identification of certain elements. ? T i i ~ c rpresented at the generd scssion of the .\lilsruWee meeting of the lmprican Chemical Society, Xrrch 2 5 . 1913.
venient attachment which can be used on any of t h e m e l l - k n o ~ ~Balopticons n possessing a lathr hed. The result was a light and easily adjustahlc apparatus which is shown in Fig. I . The projection apparatus consists of a Ralopticon set up for lantern slide projection hut with an extra standard, upon whic.h t h e adjustable slit is carried, hetween the condenser system and the projection lens and to the bcd of this Balopticon, the c o ~ n plementary color apparatus is attached as illustratd. This instrument consists of a short optical bench reference which may be adjusted to any angle to the bed to which it is attached and which supports the follom*ingaccessories: prism for carbon bisulfide or I, A any other liquid. TI. An Iris diaphragm and light shield.
holding
j u i y , 1913
T I I E JOC;I,-ere thcn shown.) The spectra of gaseous elements have not been projected, owing t o the fact that sufficient illumination could not be secured. The transformer type of sprctral tube, Fig. 4 , as designed by Dr. P. G. Nutting overcomes this difficulty for, ow-ing t o its construction in xvhich a largc capillary is employed . . with correspondingly large electrodes, a light 100 times as intense as that produced by the old tubes is secured. This type of transformer tube uses about I O , O O O volts which I secure by means of a Clapp-Eastman transformer operating on an alternating current of 1 1 0 volts. This is an inexpensive and vxcellent transformerand together with the tubc described gives us good illumination without noise. The holder for t h e s e tubes consists of a suitable piece of asbestos wood supported on a clamp which fits the optical bed. There is an asbestos wooden block on this which holds the tube supported by a brass plate in which the slit is cut. The p i a t E is heid in position by two posts x i t h nuts. The holder also carries two binding posts so that conncctions with the plat,inum wires of the transformer tubes can be carefully made at leisure, leaving any hurried changes t o be made with the feed xires a t the large binding screws. The holder witt the tnbc is placed in the same position as the slit fol the other experiments. Thr helium, hydrogen, and neon tubes used were loaned by Dr. Nutting. (Spectra of the three elements were then shown.) For the arc spectra a similar holder, Fig. j , is provided but in this case of slate since the resistance is such that the ~ o . o o ovolt current from the condenser will flow from one terminal t o the other through asbestos wourl. A porcelain hood with brass cap in
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which the slit is cut i s mounted t o prevent light falling into the room and the mctallic electrodes are fitted with pins as illustrated so that in changing from onc sct of electrodes to another it is only necessarv to insert them as far as the pin w11l allow them t o go and securc them with the set screws. The electrodes have chisel points. Connections with the current are made at thc binding posts. So far we have not been able to obtain a suitable screen for demonstrating the ultraviolet spectra of these arcs to any considerable number of people b u t hope t o accomplish that later. I n observing the spark spectra of metals in the ultraviolet, the projection lens is replaced by one madeofquartz and the bottle prism of carbon bisulfide by a quartz Cornu prism. Thus, w e have simple deFlC. 5 vices for certain spectrum experiments which can be carried on so that an entire class may view the results simultaneously and also used as a supplement to the table spectroscope. I t is hoped that those interested in the subject will find the experiments useful in their work. I wish t o give proper recognition to Dr. Mees and Dr. Nutting for the valuable aid rendered in working out the details of the experiments and offering valuable suggestions and to Mr. Patterson who is responsible Tor the designs of thc special apparatus. carbon holders, supporters, etc.
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BAUSCN6. LOMB OPTICALCo.
ROCXESTER.N. Y.
A SHORT METHOD TO DETERMINE THE EFFICIENCY OF OXIDES FOR GAS PURIFICATION B Y A . F. K D N D ~ X U E X Received H a y 23, 1913
The gas engineer as a rule i s not as mnch intcresterl in how much total iron oxide is contained in n given batch or shipment of oxide as he is in horn much hydrogen sulfide can be rrmoved per ton or per bushel of oxide before it is saturated and requires renewal. That the regular chemical analysis does not give him this required information is evident from the fact that one oxide containing almost twice as much Fe,O, as another, may absorb but of the amount of H,S absorbed by the latter, and it is the object of the present communication t o describe the, method developed and employed in this laboratory for the estimation of the efficiency of puriiying oxides. To determine the quantity of 13,s a given oxide would be able t o decompose, the water formed by the reaction was absorbed in a weighed tube containing
