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furic acid t o such a depth t h a t t h e t o p of t h e column of mercury in the thermometer is below the opening from the upper side-arm. T h e necessity of making correction for a portion of t h e mercury column above t h e sulfuric acid is t h u s obviated. A test of this form of t u b e has not as yet been made. TABLE111-COMPARISONOF UNIFORMITY OF TEMPERATURE THIELE TUBE -NEW FORM O F TUBE1
Duration Differof ence heating a C. Min.
THERMOMETER
S C.
102.6 103.0 102.8 102.8 102.2 102.4 103.0 103.6 104.2 104.4 105.0 105.8 106.0 105.4 103.8 104.2
T
C.
110.6 110.0 110.2 111.2 110.6 110.4 111.0 111.6 112.8 113.2 113.8 114.4 114.4 113.0 112.0 111.4
8.0 7.0 7.4 8.4 8.4 8.0 8.0 8.0 8.6 8.8 8.8 8.6 8.4 7.6 8.2 7.2
Maximum change of thermometer S. . Maximum change of thermometer T . . ,. Average reading of thermometer S . . . Average readine of thermometer T.;. Average difference of thermometers. . . , , .
r.. . . .
. .. .
. .. . . .. .. . ...
..1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 3.8' 4.4O 103.8' 111.9' 8.1
Duration of ence heating C. Min.
THERMOMETER Differ,
T
S C.
132.2 131.8 132.6 131 .O 131.4 132.2 132.6 132.6 131.8 131.2 130.8 130.6 130.6 130.8 131.0 131.6
C.
132.8 132.8 131.8 131.4 131.4 132.2 132.8 132.6 131.6 131.2 130.8 130.6 130.6 131.0 131.2 131.6
0.6 1 .O 0.8 0.4 0.0 0.0 0.2 0.0 0.2 0.0 0.0 0.0 0.0 0.2 0.2 0.0
Maximum channe thermometer S y . . Maximum change thermometer T . , Average reading thermometer S.. .Averape readine theFmometer Tr.. Average difference thermometers.
*. 1 2
9 10 11 12 13 14 15
of
. .of.
.. . . . . .of. of . .-. of ......
2.0° 2.2' 131.55O 131.65O 0.1
T h e determination of melting points with this new form of t u b e is much more convenient and accurate if the t u b e is heated electrically rather t h a n b y a gas flame. T o prepare the t u b e for electric heating, t h a t portion of the t u b e marked A (Fig. I ) , extending from B t o t h e point where A t u r n s upward, is first covered with a single layer of thin asbestos paper, a n d t h e n wound with about t e n t u r n s of nichrome wire, No. 26, B and S gauge (about 0.016 in. in diam.). T h e wire is t h e n covered with a layer of asbestos cement t o a depth of about 5 mm. These tubes m a y be made of ordinary soft glass, b u t Pyrex glass is preferable. NEW FORMS OF COMBUSTION APPARATUS FOR USE IN GAS ANALYSIS' By E. R. Weaver and P. G. Ledig U. S. BUREAU OF STANDARDS, WASHINGTON, D. C. Received August 12, 1919
This paper describes two new forms of combustion a p p a r a t u s for use in gas analysis. T h e first is a n improved form of t h e Dennis a n d Hopkins* combustion pipette. T h e second is a combustion capillary of small size somewhat similar t o those of Hempels a n d Levy,4 containing a n electrically heated platinum wire. COMBUSTION PIPETTE
T h e combustion apparatus usually known as t h e Dennis a n d Hopkins pipette, i n which a platinum wire is placed in a pipette of sufficiently large size t o hold all the sample t o be burned, together with t h e oxygen necessary t o burn i t , has been made in many forms. I n all of these, however, two leads are brought into Published by permission of the Director of the Bureau of Standards. J . A m . Chem. SOC.,21 (1899), 398. a 2. angew. Chem., 26 (1912), 1841. 4 J . SOC. Chem. I n d . , 31 (1912), 1153. 1
2
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12,
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t h e b o t t o m of the pipette, usually through a r u b b e r stopper, a n d carried through the confining liquid t o near t h e t o p of t h e bulb where t h e y connect t o t h e platinum wire. T h e unsatisfactory features of t h e a p p a r a t u s are as follows: I-It is difficult to make the stopper a t the bottom of the pipette and the connections through it perfectly tight. The leakage of mercury is easily detected, but the pipette may be tight to mercury and allow air to leak in when its contents are under reduced pressure, and such a leak is very likely to be overlooked for a long time. 2-The weight of the mercury in such a pipette produces a serious danger of its forcing out the stopper and spilling the mercury. 3-In order to insulate the leads it is necessary to enclose one or both of them in glass tubes. The platinum wire is usually sealed through these tubes and the connection with the lead made inside the glass tube. This is a rather difficult form of construction and one hard to repair. The point a t which the wire is sealed through the insulating tube is the most likely to crack in the whole apparatus, and such cracking is very likely to cause an undetected leak. If the leads pass through the glass and the active wire is crimped on, as is sometimes done, the junction usually has the highest resistance of any part of the circuit and is first to fail in use. A solder cannot, of course, be used in the presence of mercury. As the apparatus is frequently constructed, sufficient relative motion between the leads to distort or even break the platinum wire is possible. 4-The necessity of bringing two leads and a tube for the flow of the confining liquid out a t the bottom of the pipette makes it difficult to support so heavy a weight without mqunting it on a more or less bulky supporting frame. 5-In order to replace the platinum wire it is always necessary to completely drain the pipette and usually to disconnect it en tirely.
T h e pipette shown in Fig. I was designed t o overcome these difficulties. It is made of Pyrex glass, has a volume of between 1 2 5 a n d 1 5 0 cc., a n d is generally used with mercury as a confining liquid. T h e t w o short side-tubes through which t h e platinum wire is strung are slightly tapered a n d a cap made of soft glass is fitted t o t h e outside of this taper. A detail of this construction is shown in Fig. j. Through t h e end of this cap a heavy platinum wire is sealed. T h e wire is formed into a loop a n d t h e short end also sealed into t h e glass, as i t has been found t h a t this gives much greater strength a n d lessens t h e danger of breaking off the wire a t t h e surface of t h e glass. It is usually best t o have t h e long end of t h e wire, inside t h e cap, long enough t o go u p into t h e short side-tube a t least half a centimeter, since t h e Khotinsky cement used in fastening on the cap m a y seal off t h e inner tube. For t h e coil which is s t r u n g through t h e pipette, 5 mil (0.125 mm. diameter) platinum wire has been found t h e best, though this is smaller t h a n is commonly used. I t has been found very satisfactory, however, because much less current is required t o heat t h e wire t o a dull glow t h a n is necessary with heavier wire, a n d consequently the whole pipette is n o t heated t o so high a temperature. A finer wire is n o t stiff enough t o hold a good coil. About 7 in. of t h e wire are wound t o a compact spiral on a large needle or heavy wire, leaving a n inch or more of straight wire a t each end. I t is best t o use a piece of brass or other stiff wire df small
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Apr., 1920
diameter t o string this coil through t h e pipette. T h e projecting tips of t h e straight ends of t h e platinum wire a r e bent over the edge of the side-tube after the spiral has been pulled tight. T h e caps are t h e n fastened on t h e side-tubes with Khotinsky cement, t h e whole cap a n d side-tube being gently warmed over t h e Bunsen burner until the cement flows smoothly in between.
w
Fig. I
369
p u t together in good form, a n d must be rebuilt when either t h e wire or t h e rubber t u b i n g requires replacement. T h e three forms of combustion capillary described below are made of Pyrex glass. They are of a new t y p e which has t h e following advantages: I-The wire is easily replaced without disturbing the tube which may be permanently connected to the remainder of the gas analysis apparatus. n-There are no rubber connections near the hot wire. 3-The tube is easy to make and to keep gas-tight. 4-It is not very difficult for an amateur glass blower to make and should be quite inexpensive if made commercially. T h e simplest form is t h a t shown in Fig. 2 . T h e portion containing t h e coil has a n inside diameter of about 3 mm. a n d t h e connecting capillary tubing has a n inside diameter of about I mm. T h e platinum wire is made into a coil a n d drawn into place b y t h e use of another wire, as in t h e case of t h e pipette previously described. T h e caps are made of soft glass exactly like those for t h e pipette a n d are fastened on with Khotinsky cement. T h e cap a n d side-tube are t h e n partly filled with mercury t o make electrical contact. Water or mercury may be used as t h e confining liquid, b u t mercury has a tendency t o foul the t u b e with oxide in the course of several analyses.
f 4-92
When this cools, t h e Khotinsky holds t h e wire coil in place a n d fastens on t h e cap t o make a n air-tight joint. When t h e pipette is filled with mercury, t h e cups a n d side-tubes are filled too, a n d contact is made between the platinum wire in t h e cup a n d t h e heating coil. This pipette gives satisfactory service over a very long period without renewal of t h e wire if care is used, b u t if t h e wire is broken or t h e coil gets too slack in t h e pipette, only a few minutes of work are necessary t o replace i t . COlfIBUSTION CAPILLARY
For t h e determination of small amounts of combustible gas in t h e presence of air, oxygen, or a n inert gas, or for the determination of small amounts of oxygen in a combustible gas, there is a considerable advantage in t h e use of a combustion capillary similar t o t h a t devised by Levy.l T h e t u b e there described, in which a platinum wire is sealed into a q u a r t z capillary b y means of molybdenum leads, is very satisfactory in service; b u t t h e coil cannot be replaced if broken or burned out, a n d t h e device is expensive a n d difficult t o obtain. A similar capillary devised b y Levy, b u t having t h e lead wires passing through rubber stoppers, is very unsatisfactory from several standpoints. T h e capillaries of Hempell a n d White2 have objectionable rubber connections between t h e q u a r t z t u b e a n d t h e glass tubes which carry the lead wires. T h e Hempel apparatus, a t least, is also hard t o cit. “Gas and Fuel Analysis,” p. 49, McGraw-Hill, New York, 1913.
1 LOC. 2
ll i
U t. . Fcig.5
fl-9.4
When water is used as t h e confining liquid, i t is b n o t i t o fill t h e side-tube completely with mercury on account of this oxidation. T h e bulb-like enlargement is made in t h e side-tubes t o prevent the trapping of gas when the system is filled with water after a n analysis, during which some of t h e water has evaporated from t h e side-tubes. I n use, a double Hempel bulb or similar arrangement is connected t o t h e lower end of t h e t u b e t o confine t h e gas as i t is passed back and forth. T h e first form has proved satisfactory if carefully used, b u t if water is passed into i t while i t is h o t from a combustion, it is likely t o crack. Moreover methane
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combustions, which require a very hot wire, h a v e i n one or two cases so softened t h e t u b e t h a t it was bent a n d t h e platinum wire fused t o t h e glass. This difficulty c a n be overcome b y making t h e t u b e of quartz, but t h e advantages of using Pyrex glass a r e such that t w o other forms were developed i n which t h e t u b e is k e p t immersed i n a water bath. Fig. 3 shows t h e first form. It is made exactly t h e s a m e as that shown i n Fig. 2 except t h a t t h e lower capillary tube is sealed t o the side of t h e lower side-tube a n d is made with a goose-neck curve which allows a beaker or similar water b a t h t o be slipped u p over t h e t u b e from beneath. If distilled water is used i n this b a t h , n o trouble is experienced f r o m
Vol.
By B. R. Tunison U. S.
INDUSTRIAL
ALCOHOLCo.,27 WILLIAMST., N E W YORK,N Y. INTRODUCTION
To attempt to predict the future of industrial alcohol is similar in many respects to making an attempt to foretell the outcome of a battle in a great war. The phases of the question are so numerous and complex and there are so many interdependent influences involved that any one would presume a great deal who attempted to predict with any degree of definiteness the future of industrial alcohol. However, if present influences are considered, it is possible to anticipate a t least a few of the more important developments more or less accurately. IMPORTANCE O F ALCOHOL INDUSTRIALLY
The following statement made by a joint select committee of Congress in its official report is fully as true to-day as it was the day it was made, some 2 0 years ago. The uses of alcohol other than as a beverage are more largely and widely extended than is generally supposed. But while the use of alcohol as a beverage is purely voluntary its employment for all other purposes is legitimate, beneficial, and necessary. No article entering into manufacture or the arts, whether of domestic or foreign production, performs more legitimate or beneficial functions. There is scarcely a manufacturer in the country who does not use alcohol in the production of his goods to a greater or less extent. Of the various alcohols which have been of industrial importance ethyl alcohol is unquestionably the most important. This alcohol has been subjected to severe trials in the past and burdened by taxes which have caused very great limitations to its legitimate uses. In the industries many costly substitutes have been made because pure ethyl alcohol was obtainable only a t prohibitive prices, due to excessive taxes, and because the denatured grades were not suitable for many special purposes. The importance of methyl alcohol industrially is second only to that of ethyl alcohol. There seems little doubt that this is due to commercial influences rather than to chemical reasons. In the United States it has been substituted for ethyl alcohol for a great many purposes for which it is not so well suited, because of the rules, regulations, and taxes surrounding the manufacture, distribution, and use of ethyl alcohol. During and since the recent war the demand for methyl alcohol has greatly increased, due in part to the rapidly growing dye industry in this country and also to the enormous export demands because of its limited production in other countries. 1 Read before the N e w York Section of the American Chemical Society, Chemists' Club, New York, N. Y.,October 10, 1919.
No. 4
electrolysis between t h e lead wires. T h e only objection t o t h i s form of t u b e , of which t w o h a v e given satisfactory service over a period of several months, is t h a t i t s awkward shape makes i t fragile. Consequently t h e t h i r d f o r m shown i n Fig. 4 w a s developed. It requires care i n making t o prevent t h e gas being t r a p p e d i n t h e bends of t h e main t u b e when refilling after a combustion. It is also somewhat more difficult t o insert t h e platinum coil, usually requiring a wire hook t o catch t h e e n d of t h e stringing wire a n d d r a w it around t h e s h a r p bend at t h e upper end, b u t when i t is once made a n d set u p i n t h e water bath, as shown b y t h e light lines i n t h e figure, it gives complete satisfaction.
ADDRESSES AND CONTRIBUTED ARTICLES THE FUTURE OF INDUSTRIAL ALCOHOLS'
12,
I
Its price has more than doubled since the beginning of the war. This increase was not only justified, but necessary, because of the fact that the production of methyl alcohol is limited by the quantity of wood carbonized and because of the low selling price of calcium acetate. It is not likely that this situation will be relieved until such time as methyl alcohol is used only when necessary and not as a substitute for ethyl alcohol in essentially ethyl alcohol processes. Unless the demand for this alcogol greatly exceeds all present expectations, the standard destructive distillation method for the production of methyl alcohol will probably be used indefinitely. Modifications are being made from time to time, but the basic process is the same and needs no particular discussion a t this time. The future development of the methyl alcohol industry in this country should be very rapid. As the chemical industries are progressing so rapidly, greater and greater quantities of this very essential alcohol will be used. If, as is hoped and expected, the United States becomes one of the largest exporters of dyes, chemicals, and allied products, the use of methyl alcohol will constantly increase. New uses will undoubtedly develop and as these new uses and new industries are expanded methyl alcohol will be of ever-increasing importance in this country. While many other alcohols are of commercial significance in the United States, their production to any extent in this country has been very recent. Up to the time of the World war it was possible to import an adequate supply. Durhg the war many substances in the production of which the higher alcohols are necessary could not be imported and the importation of the alcohols was almost completely cut off. This had the effect of greatly stimulating the production of these alcohols in the United States. Up to this time large quantities were discarded by many manufacturers because they were in admixture with other bulky waste materials, and their separation more or less difficult. Some manufacturers sold for solvent purposes mixtures of these alcohols, because they could not make the separation and compete with the alcohols brought into the United States from foreign parts. The production, separation, and purification of higher alcohols is one of the new and rapidly growing industries of this country and should be supported by all users of these products to the greatest possible extent. It is hoped that this industry may survive any periods of depression that may be encountered and that the United States may be independent of any importation of these valuable and necessary alcohols. The question of the production of ethyl alcohol is so important that it warrants our brief consideration a t this time.
