_Table to facilitate the Correction of the Volume of Gas at different Temperatures and under different Atmospheric Pressures._
_____________________________________________________ THERMOMETER. BAR. _______________________________________________ 46 48 50 52 54 56 _____ _______ _______ _______ _______ _______ _______ 28.4 0.979 0.974 0.970 0.965 0.960 0.955 28.5 0.983 0.978 0.973 0.968 0.964 0.959 28.6 0.986 0.981 0.977 0.972 0.967 0.962 28.7 0.990 0.985 0.980 0.975 0.970 0.966 28.8 0.993 0.988 0.984 0.979 0.974 0.969 28.9 0.997 0.992 0.987 0.982 0.977 0.973 29.0 1.000 0.995 0.990 0.986 0.981 0.976 29.1 1.004 0.999 0.994 0.989 0.984 0.979 29.2 1.007 1.002 0.997 0.992 0.988 0.982 29.3 1.011 1.005 1.001 0.996 0.991 0.986 29.4 1.014 1.009 1.004 0.999 0.995 0.990 29.5 1.018 1.013 1.008 1.003 0.998 0.993 29.6 1.021 1.016 1.011 1.006 1.001 0.996 29.7 1.025 1.019 1.015 1.010 1.005 1.000 29.8 1.028 1.023 1.018 1.013 1.008 1.003 29.9 1.031 1.026 1.022 1.017 1.012 1.007 30.0 1.035 1.030 1.025 1.020 1.015 1.010 30.1 1.038 1.033 1.029 1.024 1.019 1.014 30.2 1.042 1.037 1.032 1.027 1.022 1.017 30.3 1.045 1.040 1.036 1.030 1.025 1.020 30.4 1.049 1.044 1.039 1.034 1.029 1.024 30.5 1.052 1.047 1.042 1.037 1.032 1.027 _____ _______ _______ _______ _______ _______ _______ _____________________________________________________ THERMOMETER. BAR. _______________________________________________ 58 60 62 64 66 68 _____ _______ _______ _______ _______ _______ _______ 28.5 0.954 0.949 0.944 0.939 0.934 0.929 28.6 0.958 0.953 0.947 0.943 0.938 0.932 28.7 0.961 0.956 0.951 0.946 0.941 0.936 28.8 0.964 0.959 0.954 0.949 0.944 0.939 28.9 0.968 0.963 0.958 0.953 0.948 0.942 29.0 0.971 0.966 0.961 0.956 0.951 0.946 29.1 0.975 0.969 0.964 0.959 0.954 0.949 29.2 0.978 0.973 0.968 0.963 0.958 0.952 29.3 0.981 0.976 0.971 0.966 0.961 0.956 29.4 0.985 0.980 0.975 0.969 0.964 0.959 29.5 0.988 0.983 0.978 0.973 0.968 0.962 29.6 0.992 0.986 0.981 0.976 0.971 0.966 29.7 0.995 0.990 0.985 0.980 0.974 0.969 29.8 0.998 0.993 0.988 0.983 0.978 0.972 29.9 1.002 0.997 0.991 0.986 0.981 0.976 30.0 1.005 1.000 0.995 0.990 0.985 0.979 30.1 1.009 1.003 0.998 0.993 0.988 0.983 30.2 1.012 1.007 1.002 0.996 0.991 0.986 30.3 1.015 1.010 1.005 1.000 0.995 0.989 30.4 1.019 1.014 1.008 1.003 0.998 0.993 30.5 1.022 1.017 1.012 1.006 1.001 0.996 _____ _______ _______ _______ _______ _______ _______ _____________________________________________ THERMOMETER. BAR. _______________________________________ 70 72 74 76 78 _____ _______ _______ _______ _______ _______ 28.4 0.921 0.915 0.910 0.905 0.900 28.5 0.924 0.919 0.914 0.908 0.903 28.6 0.927 0.922 0.917 0.912 0.906 28.7 0.931 0.925 0.920 0.915 0.909 28.8 0.934 0.929 0.924 0.918 0.913 28.9 0.937 0.932 0.927 0.921 0.916 29.0 0.941 0.935 0.930 0.925 0.919 29.1 0.944 0.939 0.933 0.928 0.923 29.2 0.947 0.942 0.937 0.931 0.926 29.3 0.950 0.945 0.940 0.935 0.929 29.4 0.954 0.949 0.943 0.938 0.932 29.5 0.957 0.952 0.947 0.941 0.936 29.6 0.960 0.955 0.950 0.944 0.939 29.7 0.964 0.959 0.953 0.948 0.942 29.8 0.967 0.962 0.957 0.951 0.946 29.9 0.970 0.965 0.960 0.954 0.949 30.0 0.974 0.968 0.963 0.958 0.952 30.1 0.977 0.972 0.966 0.961 0.955 30.2 0.980 0.975 0.970 0.964 0.959 30.3 0.984 0.978 0.973 0.968 0.962 30.4 0.987 0.982 0.976 0.971 0.965 30.5 0.990 0.985 0.980 0.974 0.969 _____ _______ _______ _______ _______ _______
For the detection of phosphine, Berge's solution may be used. It is a "solution of 8 to 10 parts of corrosive sublimate in 80 parts of water and 20 parts of 30 per cent. hydrochloric acid." It becomes cloudy when gas containing phosphine is passed into it. It is, however, applied most conveniently in the form of Keppeler's test-papers, which have been described in Chapter V. Test-papers for phosphine, the active body in which has not yet been divulged, have recently been produced for sale by F. B. Gatehouse.
The estimation of phosphine will usually require to be carried out either (1) on gas directly evolved from carbide in order to ascertain if the carbide in question yields an excessive proportion of phosphine, or (2) upon acetylene which is presumably purified, drawn either from the outlet of the purifier or from the service-pipes, with the object of ascertaining whether an adequate purification in regard to phosphine has been accomplished. In either case, the method of estimation is the same, but in the first, acetylene should be specially generated from a small representative sample of the carbide and led directly into the apparatus for the absorption of the phosphine. If the acetylene passes into the ordinary gasholder, the amount of phosphine in gas drawn off from the holder will vary from time to time according to the temperature and the degree of saturation of the water in the holder-tank with phosphine, as well as according to the amount of phosphine in the gas generated at the time.
A method frequently employed for the determination of phosphine in acetylene is one devised by Lunge and Cedercreutz. If the acetylene is to be evolved from a sample of carbide in order to ascertain how much phosphine the latter yields to the gas, about 50 to 70 grammes of the carbide, of the size of peas, are brought into a half-litre flask, and a tap-funnel, with the mouth of its stem contracted, is passed through a rubber plug fitting the mouth of the flask. A glass tube passing through the plug serves to convey the gas evolved to an absorption apparatus, which is charged with about 75 c.c. of a 2 to 3 per cent. solution of sodium hypochlorite. The absorption apparatus may be a ten-bulbed absorption tube or any convenient form of absorption bulbs which subject the gas to intimate contact with the solution. If acetylene from a service-pipe is to be tested, it is led direct from the nozzle of a gas- tap to the absorption tube, the outlet of which is connected with an aspirator or the inlet of an experimental meter, by which the volume of gas passed through the solution is measured. But if the generating flask is employed, water is allowed to drop from the tap-funnel on to the carbide in the flask at the rate of 6 to 7 drops a minute (the tap-funnel being filled up from time to time), and all the carbide will thus be decomposed in 3 to 4 hours. The flask is then filled to the neck with water, and disconnected from the absorption apparatus, through which a little air is then drawn. The absorbing liquid is then poured, and washed out, into a beaker; hydrochloric acid is added to it, and it is boiled in order to expel the liberated chlorine. It is then usual to precipitate the sulphuric acid by adding solution of barium chloride to the boiling liquid, allowing it to cool and settle, and then filtering. The weight of barium sulphate obtained by ignition of the filter and its contents, multiplied by 0.137, gives the amount of sulphur present in the acetylene in the form of sulphuretted hydrogen. The filtrate and washings from this precipitate are rendered slightly ammoniacal, and a small excess of "magnesia mixture" is added; the whole is stirred, left to stand for 12 hours, filtered, the precipitate washed with water rendered slightly ammoniacal, dried, ignited, and weighed. The weight so found multiplied by 0.278 gives the weight of phosphorus in the form of phosphine in the volume of gas passed through the absorbent liquid.
Objection may rightly be raised to the Lunge and Cedercreutz method of estimating the phosphine in crude acetylene on the ground that explosions are apt to occur when the gas is being passed into the hypochlorite solution. Also it must be borne in mind that it aims at estimating only the phosphorus which is contained in the gas in the form of phosphine, and that there may also be present in the gas organic compounds of phosphorus which are not decomposed by the hypochlorite. But when the acetylene is evolved from the carbide in proper conditions for the avoidance of appreciable heating it appears fairly well established that phosphorus compounds other than phosphine exist in the gas only in practically negligible amount, unless the carbide decomposed is of an abnormal character. Various methods of burning the acetylene and estimating the phosphorus in the products of combustion have, however been proposed for the purpose of determining the total amount of phosphorus in acetylene. Some of them are applicable to the simultaneous determination of the total sulphur in the acetylene, and in this respect become akin to the Gas Referees' method for the determination of the sulphur compounds in coal-gas.
Eitner and Keppeler have proposed to burn the acetylene on which the estimation is to be made in a current of neat oxygen. But this procedure is rather inconvenient, and by no means essential. Lidholm liberated acetylene slowly from 10 grammes of carbide by immersing the carbide in absolute alcohol and gradually adding water, while the gas mixed with a stream of hydrogen leading to a burner within a flask. The flow of hydrogen was reduced or cut off entirely while the acetylene was coming off freely, but hydrogen was kept burning for ten minutes after the flame had ceased to be luminous in order to ensure the burning of the last traces of acetylene. The products of combustion were aspirated through a condenser and a washing bottle, which at the close were rinsed out with warm solution of ammonia. The whole of the liquid so obtained was concentrated by evaporation, filtered in order to remove particles of soot or other extraneous matter, and acidified with nitric acid. The phosphoric acid was then precipitated by addition of ammonium molybdate.
J. W. Gatehouse burns the acetylene in an ordinary acetylene burner of from 10 to 30 litres per hour capacity, and passes the products of combustion through a spiral condensing tube through which water is dropped at the rate of about 75 c.c. per hour, and collected in a beaker.
The burner is placed in a glass bell-shaped combustion chamber connected at the top through a right-angled tube with the condenser, and closed below by a metal base through which the burner is passed. The amount of gas burnt for one determination is from 50 to 100 litres. When the gas is extinguished, the volume consumed is noted, and after cooling, the combustion chamber and condenser are washed out with the liquid collected in the beaker and finally with distilled water, and the whole, amounting to about 400 c.c., is neutralised with solution of caustic alkali (if decinormal alkali is used, the total acidity of the liquid thus ascertained may be taken as a convenient expression of the aggregate amount of the sulphuric, phosphoric and silicic acids resulting from the combustion of the total corresponding impurities in the gas), acidified with hydrochloric acid, and evaporated to dryness with the addition towards the end of a few drops of nitric acid. The residue is taken up in dilute hydrochloric acid; and silica filtered off and estimated if desired. To the filtrate, ammonia and magnesia mixture are added, and the magnesium pyrophosphate separated and weighed with the usual precautions.
Sulphuric acid may, if desired, be estimated in the filtrate, but in that case care must be taken that the magnesia mixture used was free from it.
Mauricheau-Beaupre has elaborated a volumetric method for the estimation of the phosphine in crude acetylene depending on its decomposition by a known volume of excess of centinormal solution of iodine, addition of excess of standard solution of sodium thiosulphate, and titrating back with decinormal solution of iodine with a few drops of starch solution as an indicator. One c.c. of centinormal solution of iodine is equivalent to 0.0035 c.c. of phosphine. This method of estimation is quickly carried out and is sufficiently accurate for most technical purposes.
In carrying out these analytical operations many precautions have to be taken with which the competent analyst is familiar, and they cannot be given in detail in this work, which is primarily intended for ordinary users of acetylene, and not for the guidance of analysts. It may, however, be pointed out that many useful tests in connexion with acetylene supply can be conducted by a trained analyst, which are not of a character to be serviceable to the untrained experimentalist. Among such may be named the detection of traces of phosphine in acetylene which has passed through a purifier with a view to ascertaining if the purifying material is exhausted, and the estimation of the amount of air or other diluents in stored acetylene or acetylene generated in a particular manner. Advice on these points should be sought from competent analysts, who will already have the requisite information for the carrying out of any such tests, or know where it is to be found. The analyses in question are not such as can be undertaken by untrained persons. The text-book on "Gas Manufacture" by one of the authors gives much information on the operations of gas analysis, and may be consulted, along with Hempel's "Gas Analysis" and Winkler and Lunge's "Technical Gas Analysis."
APPENDIX
DESCRIPTIONS OF A NUMBER OF ACETYLENE GENERATORS AS MADE IN THE YEAR 1909
(_The purpose of this Appendix is explained in Chapter IV., page 111, and a special index to it follows the general index at the end of this book._)
AMERICA--CANADA.
_Maker_: SICHE GAS CO., LTD., GEORGETOWN, ONTARIO.
_Type_: Automatic; carbide-to-water.
The "Siche" generator made by this firm consists of a water-tank _A_, having at the bottom a sludge agitator _N_ and draw-off faucet _O_, and rigidly secured within it a bell-shaped generating chamber _B_, above which rises a barrel containing the feed chamber _C_, surmounted by the carbide chamber _D_. The carbide used is granulated or of uniform size. In the generating chamber _B_ is an annular float _E_, nearly filling the area of the chamber, and connected, by two rods passing, with some lateral play, through apertures in the conical bottom of the feed chamber _C_, to the T-shaped tubular valve _F_. Consequently when the float shifts vertically or laterally the rods and valves at once move with it. The angle of the cone of the feed chamber and the curve of the tubular valve are based on the angle of rest of the size of carbide used, with the object of securing sensitiveness of the feed. The feed is thus operated by a very small movement of the float, and consequently there is but very slight rise and fall of the water in the generating chamber. Owing to the lateral play, the feed valve rarely becomes concentric with its seat. There is a cover _G_ over the feed valve _F_, designed to distribute the carbide evenly about the feed aperture and to prevent it passing down the hollow of the valve and the holes through which the connecting-rods pass. It also directs the course of the evolved gas on its way to the service-pipe through the carbide in the feed chamber _C_, whereby the gas is dried. The carbide chamber _D_ has at its bottom a conical valve, normally open, but closed by means of the spindle _H_, which is engaged at its upper end by the closing screw-cap _J_, which is furnished with a safelocking device to prevent its removal until the conical valve is closed and the hopper chamber _D_ thereby cut off from the gas-supply. The cap _J_, in addition to a leather washer to make a gas-tight joint when down, has a lower part fitting to make an almost gas-tight joint. Thus when the cap is off; the conical valve fits gas-tight; when it is on and screwed down it is gas-tight; and when on but not screwed down, it is almost gas-tight. Escape of gas is thus avoided. A special charging funnel _K_, shown in half-scale, is provided for inserting in place of the screw cap. The carbide falls from the funnel into the chamber _D_ when the chain is pulled. A fresh charge of carbide may be put in while the apparatus is in action. The evolved gas goes into the chamber _C_ through a pipe, with cock, to a dust-arrester _L_, which contains a knitted stocking lightly filled with raw sheep's wool through which the gas passes to the service- pipe. The dust-arrester needs its contents renewing once in one, two, or three years, according to the make of gas. The pressure of the gas is varied as desired by altering the height of water in the tank _A_.
When cleaning the machine, the water must never be run below the top of the generating chamber.
[Illustration: FIG. 24.--"SICHE" GENERATOR.]
AMERICA--UNITED STATES.
_Maker:_ J. B. COLT CO., 21 BARCLAY STREET, NEW YORK.
_Type:_ Automatic; carbide-to-water.
The "Colt" generator made by this firm comprises a carbide hopper mounted above a generating tank containing water, and an equalising bell gasholder mounted above a seal-pot having a vent-pipe _C_ communicating with the outer air. The carbide hopper is charged with 1/4 x 1/12 inch carbide, which is delivered from it into the water in the generating tank in small portions at a time through a double valve, which is actuated through levers connected to the crown of the equalising gasholder. As the bell of the gasholder falls the lever rotates a rock shaft, which enters the carbide hopper, and through a rigidly attached lever raises the inner plunger of the feed-valve. The inner plunger in turn raises the concentric outer stopper, thereby leaving an annular space at the base of the carbide hopper, through which a small delivery of carbide to the water in the generating tank then ensues. The gas evolved follows the course shown by the arrows in the figure into the gasholder, and raises the bell, thereby reversing the action of the levers and allowing the valve to fall of its own weight and so cut off the delivery of carbide. The outer stopper of the valve descends before the inner plunger and so leaves the conical delivery mouth of the hopper free from carbide. The inner plunger, which is capped at its lower end with rubber, then falls and seats itself moisture-tight on the clear delivery mouth of the hopper. The weight of the carbide in the hopper is taken by its sides and a projecting flange of the valve casing, so that the pressure of the carbide at the delivery point is slight and uniform.
The outside of the delivery mouth is finished by a drip collar with double lip to prevent condensed moisture creeping upwards to the carbide in the hopper. A float in the generating tank, by its descent when the water falls below a certain level, automatically draws a cut off across the delivery mouth of the carbide hopper and so prevents the delivery of carbide either automatically or by hand until the water in the generating tank has been restored to its proper level. Interlocking levers, (11) and (12) in the figure, prevent the opening of the feed valve while the cap (10) of the carbide hopper is open for recharging the hopper. There is a stirrer actuated by a handle (9) for preventing the sludge choking the sludge cock. The gas passes into the gasholder through a floating seal, which serves the dual purpose of washing it in the water of the gasholder tank and of preventing the return of gas from the holder to the generating tank. From the gasholder the gas passes to the filter (6) where it traverses a strainer of closely woven cotton felt for the purpose of the removal of any lime.
[Illustration: FIG. 25.--"COLT" GENERATING PLANT.]
Drip pipes (30) and (31) connected to the inlet- and outlet-pipes of the gasholder are sealed in water to a depth of 6 inches, so that in the event of the pressure in the generator or gasholder rising above that limit the surplus gas blows through the seal and escapes through the vent-pipe _C_. There is also a telescopic blow-off (32) and (33), which automatically comes into play if the gasholder bell rises above a certain height.
_Maker:_ DAVIS ACETYLENE CO., ELKHARDT, INDIANA.
_Type:_ Automatic; carbide-to-water.
The "Davis" generator made by this firm comprises an equalising bell gasholder with double walls, the inner wall surrounding a central tube rising from the top of the generating chamber, in which is placed a water-sealed carbide chamber with a rotatory feeding mechanism which is driven by a weight motor. The carbide falls from the chamber on to a wide disc from which it is pushed off a lump at a time by a swinging displacer, so arranged that it will yield in every direction and prevent clogging of the feeding mechanism. Carbide falls from the disk into the water of the generating chamber, and the evolved gas raises the bell and so allows a weighted lever to interrupt the action of the clockwork, until the bell again descends. The gas passes through a washer in the gasholder tank, and then through an outside scrubber to the service-pipe.
There is an outside chamber connected by a pipe with the generating chamber, which automatically prevents over-filling with water, and also acts as a drainage chamber for the service- and blow-off-pipes. There is an agitator for the residuum and a sludge-cock through which to remove same. The feeding mechanism permits the discharge of lump carbide, and the weight motor affords independent power for feeding the carbide, at the same time indicating the amount of unconsumed carbide and securing uniform gas pressure.
[Illustration: FIG. 26.--"DAVIS" GENERATOR.]
_Maker:_ SUNLIGHT GAS MACHINE CO., 49 WARREN STREET, NEW YORK.
_Type:_ Automatic; carbide-to-water.
The "Omega" apparatus made by this firm consists of a generating tank containing water, and surmounted by a hopper which is filled with carbide of 1/4-inch size. The carbide is fed from the hopper into the generating tank through a mechanism consisting of a double oscillating cup so weighted that normally the feed is closed. The fall of the bell of the equalising gasholder, into which the gas evolved passes, operates a lever _B_, which rotates the weighted cup in the neck of the hopper and so causes a portion of carbide to fall into the water in the generating tank. The feed-cup consists of an upper cup into which the carbide is first delivered. It is then tipped from the upper cup into the lower cup while, at the same time, further delivery from the hopper is prevented.
Thus only the portion of carbide which has been delivered into the lower cup is emptied at one discharge into the generator. There is a safety lock to the hopper cap which prevents the feeding mechanism coming into operation until the hopper cap is screwed down tightly. Provision is made for a limited hand-feed of carbide to start the apparatus. The gasholder is fitted with a telescoping vent-pipe, by which gas escapes to the open in the event of the bell being raised above a certain height. There is also an automatic cut-off of the carbide feed, which comes into operation it the gas is withdrawn too rapidly whether through leakage in the pipes or generating plant, or through the consumption being increased above the normal generating capacity of the apparatus. The gas evolved passes into a condensing or washing chamber placed beneath the gasholder tank and thence it travels to the gasholder. From the gasholder it goes through a purifier containing "chemically treated coke and cotton" to the supply-pipe.
[Illustration: FIG. 27.--"OMEGA" GENERATOR.]
1 Vent-cock handle.
2 Residuum-cock handle.
3 Agitator handle.
4 Filling funnel.
5 Water overflow.
6 Hopper cap and lever.
7 Starting feed.
8 Rocker arm.
9 Feed connecting-rod.
A Pawl.
B Lever for working feed mechanism.
C Guide frame.
D Residuum draw-off cock.
G Chain from hopper cap to feed mechanism.
H Blow-off and vent-pipe connexion.
I Gas outlet from generator.
J Gas service-cock.
K Filling funnel for gasholder tank.
L Funnel for condensing chamber.
M Gas outlet at top of purifier.
N Guides on gas-bell.
O Crosshead on swinging pawl.
P Crane carrying pawl.
Q Shaft connecting feed mechanism.
R Plug in gas outlet-pipe.
S Guide-frame supports.
U Removable plate to clean purifier.
Z Removable plate to expose feed-cups for cleaning same.
AUSTRIA-HUNGARY