T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Mar., 1 9 1 6
No. 2 was made by absorbing t h e hydrogen with colloidal palladium solution a n d burning t h e methane with a hot platinum spiral. TABLE V-PERCENTAGE
ANALYSESOF A MIXTUREOF NATURAL GAS AND HYDROGEN BY T W O DIFPERENT METHODS NO. ANALYSESBY Hz Natural gas 1 Copper oxide and slow combustion. . . . . . 5 0 . 7 48.3 2 Colloidal palladium and slow combustion. , 5 0 . 2 48.1
.
The above analyses showed t h a t t h e paraffin hydrocarbons higher t h a n methane were not oxidized, a t least in any significant amount, by t h e copper oxide. Lastly, there is shown work upon t h e analysis of t h e artificially mixed coal and water gas of Pittsburgh. The first analysis was made by burning t h e carbon monoxide a n d hydrogen with copper oxide a t about 290' C. a n d paraffin hydrocarbons in t h e slow-combustion pipette with a hot platinum spiral. The second analysis was made by using copper oxide at about 290' C. t o burn the carbon monoxide, a solution of colloidal palladium t o absorb t h e hydrogen, a n d a hot platinum spiral t o burn t h e paraffin hydrocarbons. The third analysis was made by burning carbon monoxide and hydrogen at about 290' C. with copper oxide a n d by burning t h e paraffin hydrocarbons at a red heat with copper oxide. TABLE VI-PERCENTAGEANALYSESOF
23 1
capillary of I . j mm. internal diameter. J is t h e brass body holding t h e combustion tube. K is a three-way glass cock of z mm. bore. ;L' is a two-way glass cock of j mm. bore. P is a glass-covered pipette stand whose height is adjustable. Q is a set screw for adjustment of P. J , t h e brass body holding t h e combustion tube, has two small holes, a little smaller t h a n I . j mm. diameter, drilled from the posterior side into of t h e body J. Into these are fitted t h e two legs of a platinum combustion tube of I . j mm. outside and. 0 . j mm. inside diameter. Th'e small holes are I cm. apart. The platinum tube is about I O t o 1 1 cm. long and is bent to form a U, t h e two legs of which run parallel about I cm. apart. Into t h e forepart of t h e body two large holes, about 8 mm. in diameter, are drilled, whose centers meet t h e centers of t h e I . j rnm. holes drilled from t h e rear. The brass body has grooves milled in large enough t o have a water circulation t o keep t h e rubber tubing cool, which holds t h e bent glass capillaries of I . 5 mm. bore fitting tightly into t h e larger holes A,A. These
THE ARTIFICIAL ILLUMINATING GAS
O F PITTSBURGH
No. I..... 2,.... 3.....
COS Illuminants 2.5 2.6 2.4
7.4 7.0 7.5
0% 0.4 0.4 0.4
CO
Hz
11.5
43.6 43.9 43.4
11.7 11.5
CH4 CXHB iVz TOTAL 30.6 2 . 1 1 . 9 100.0 3 0 . 7 2.2 1.5 1 0 0 . 0 3 0 . 4 2 . 2 2 . 2 100.0
SUMMARY
I-The authors' experience with the copper-oxide method, devised by Jager for t h e fractional combustion of hydrogen a n d carbon monoxide, is described. 11-A gas-analysis apparatus, embodying a copperoxide tube somewhat different in form from others on t h e market, but containing no new principle, is also described. 111-A temperature of t h e copper oxide of between 275' a n d 300' is adapted for burning hydrogen and carbon monoxide in a wide variety of mixtures. Most previous experimenters have adopted temperatures in this range. LABORATORY GAS INVESTIGATIONS BUREAUOF
MINES, PITTSBURGH, P A .
A NEW ACCURATE METHOD OF GAS ANALYSIS By O . , A . KRONE Received August 26, 1915
Figs. I a n d I1 show t h e apparatus used for estimating t h e quantities of carbon dioxide, illurninants, oxygen, carbon monoxide, methane, ethane, hydrogen a n d nitrogen in gaseous mixtures. B,B1 are I O O cc. burettes graduated t h e entire length in 0.1 cubic centimeter. C,CI are water jackets for t h e burettes. D is a three-way glass Geissler cock of 2 mm. bore. E,E1 are bent capillary tubes of I mm. bore. F is a three-way Geissler cock, G is a two-way cock having a T capillary fused t o F. H is a bent I . 5 mm. bore capillary, whose orifice, HI, is melted t o measure 0.3 mm. I " i s a piece of glass tubing having walls of sufficient strength, and a n internal diameter of 1.75 cm. drawn down t o a
glass capillaries are bent so t h a t t h e combustion t u b e protrudes in t h e rear of t h e apparatus. Around t h e brass body is soldered a piece of sheet copper t o form a cup for water. The platinum tube is then soldered in, gas-tight. If mercury is used as t h e confining fluid in burette B, t h e platinum tube is either brazed or silvered in, gas-tight. The ends of the platinum tube are tapered so t h a t tight joints are secured by forcing t h e ends into t h e brass body. A small piece of asbestos paper is fitted onto t h e platinum capillary t o prevent t h e unused heat from softening t h e solder. A Meker or Bausch and Lomb high temperature burner is used t o heat t h e tube and is adjusted t o position with a n iron clamp fastened t o t h e apparat u s support. All rubber connections should be made with t h e best heavy-walled rubber tubing which should be of small enough size t o give a tight joint. All glass capillaries should fit shoulder t o shoulder
232
T H E J O C R N A L O F I N D C S T R I A L AiVD E N G I N E E R I N G C H E M I S T R Y
when connections are made, and all rubber connections should be wired by iron wire I mm. in diameter, a t t h e edge of t h e tubing. All joints t h a t are t o be rigid should be stiffened by wrapping a piece of sheet copper of suitable size around t h e rubber within t h e space of t h e two iron wires which hold t h e tubing tight at t h e edge and then wiring this sheet on tightly with three iron wires. I mm. in diameter. A S S E b I B L Y OF A P P A R A T U S
D is fastened t o t h e body of burette B with rubber tubing, wired and stiffened. K is fastened in like manner t o B1. B is then p u t into C, t h e rubber stoppers put into place a t t h e ends of C. E a n d El are fastened t o D and K with rubber tubing a n d wired. T h e burette B is fastened t o t h e right side of apparat u s support with a universal clamp. The burette BI is fastened t o the left side in t h e same way. F a n d G are connected t o D, mired a n d stiffened. H is fitted tightly into I a t HI with a piece of rubber t u b ing. I is connected t o J with rubber tubing. J is connected t o K in like manner. P a n d PI are then adjusted. N is connected t o B1, wired, stiffened a n d fastened t o table by wiring i t t o a large cork nailcd t o t h e table. N is then connected with 36 inches of heavy-walled mercury rubber tubing, wired, a n d connected t o t h e mzrcury aspirator bottle which connection is also wired. The lower 18 in. of this tubing should be
.
FIG 11-DETAILOF CAPILLARY AKD TRAP
wrapped with good adhesive tape t o prevent t h e mercury from bulging through t h e tubing when t h e aspirator bottle is raised. All stoppers are wired t o t h e cocks. The mercury aspirator bottle is then filled with mercury. A is connected and wired t o 40 in. of smooth bore heavy-walled, best grade rubber tubing, which is then connected t o a 500 cc. aspirator bottle which is filled with one part of HC1 (sp. gr. I . 2 ) t o I O parts distilled water. The water jackets are filled with distilled water. If preferred, manometers a n d compensating tubes may be added t o t h e burette; otherwise compared Centigrade thermometers should be inserted in t h e water jackets through t h e t o p rubber stoppers. Mercury should not be allowed t o get into the platinum capillary nor should explosive mixtures be run through too fast when t h e joints are soldered, as this will destroy t h e solder joints. For accuracy it is preferred t o use mercury in burette B also. A small amount of water on t h e surface of t h e mercury may be allowed, provided t h e burettes are cali-
Vol. 8, No. 3
brated for mercury and the water meniscus for t h e amount of water on the mercury surface. REAGEKTS USED
(I)-One part of purified stick potash t o one part pure water by weight: 1 5 0 cc. of this solution are poured into a stoppered, single Hempel pipette filled with clean iron turnings t o increase t h e absorbing surface of the potash. (a)-Nordhausen sulfuric acid, or where preferable, saturated bromine water. (3)--Yello~ phosphorus cast into 5 mm. sticks set upright in a stoppered, single Hempel pipette covered by I jo cc. of pure distilled water. The Hempel pipette body is painted black. A '/*-inch strip extending lengthwise on t h e front side of t h e phosphorus bulb a n d t h e capillary are left unpainted so t h a t t h e action of t h e phosphorus may be observed. (4)-=1 stoppered, double Hempel pipette filled completely with straight I . j mm. copper wires a n d covered by 1 2 5 cc. of t h e following solution: one part b y weight of ammonium hydroxide (sp. gr. 0.90) t o four parts by weight of pure distilled water. A large excess of ammonium chloride is then added t o this diluted ammonium hydroxide and a saturated solution is made a t about 80" F. After being sure t h e solution is saturated, t h e excess of ammonium chloride is allowed t o settle a n d t h e clear solution decanted into a clean flask, stoppered, a n d kept for use. This copper pipette is the best absorbing agent for oxygen b u t can not be used when carbon monoxide or dioxide i s present. Saturated ammonium chloride in ammonium hydroxide (sp. gr. 0.90) should not be used as t h e nitrogen of the theoretically ionized N H 4 is, t o a certain extent, oxidized t o free nitrogen when a 99y0 oxygen is analyzed. Weaker solutions of ammonium chloride should likewise be avoided. Phosphorus, according t o G. Lunge's 1914 publication, is t h e best reagent for absorbing oxygen from illuminating or heating gases. This assertion has been proven t o be correct. Low concentrations of oxygen, up t o 5 per cent oxygen, mixed with gases such as hydrogen, water gas, coal gas, etc., were separated by treatment with phosphorus and in no case was a perceptible excess contraction noticed. On t h e other hand, high concentrations of oxygen, 98.670 pure, with hydrogen a n d other combustible gases, when treated with phosphorus, showed excess contraction due to chemical combination with some of t h e hydrogen or other gas with t h e oxygen. With high concentrations of oxygen t h e phosphorus melted, trapping gas. Even air, when allowed t o come into contact with t h e phosphorus, gradually melted the phosphorus, necessitating t h e recasting of t h e phosphorus. Hence for low concentrations of oxygen, when carbon monoxide is present, phosphorus was considered t h e best reagent t o be used. The oxygen is absorbed very rapidly. As soon as t h e white phosphorus pentoxide fumes have nearly
Mar., 1916
T H E JOGrRNAL OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
settled or if t h e pentoxide fumes are washed into solution giving t h e small amount of oxygen diffused in t h e gas t h e opportunity of coming in contact with t h e moist phosphorus, as t h e pentoxide fumes retard t h e movement of t h e molecules of t h e gas, t h e absorption is complete. Further treatment of t h e gas with phosphorus causes no contraction. Phosphorus gives valuable indication of t h e complete absorption of t h e unsaturated hydrocarbons b y t h e fuming sulfuric acid or bromine water. A phosphorus pipette lasts much longer t h a n a pyrogallate pipette a n d one pipette can be used for all of t h e gases while when using alkaline pyrogallol i t is necessary t o have a separate pipette for each kind of gas analyzed. Phosphorus is much speedier in action t h a n pyrogallate; besides, continuously accurate results are obtained by its use, which can not be said of pyrogallol. Pyrogallol prepared as directed b y R. P. Anderson1 is also very unpleasant t o handle. Fuming sulfuric acid should always be fresh enough so t h a t t h e reaction between t h e oxygen a n d phosphorus is not interfered with, due t o presence of remaining hydrocarbons. For concentrations of oxygen higher t h a n 5 per cent a n d where carbon monoxide or dioxide is not present, t h e best method for absorbing oxygen is b y copper with t h e ammonium chloride solution as directed previously. Such a pipette lasts a very long time. We have used one daily for about two months without renewing any part of i t a n d i t does not at present show a n y signs of becoming exhausted. It must be remembered t o use t h e ammonium chloride solution as specified. The results obtained b y this method agree exactly with those secured by combustion. Samples of air analyzed gave a value of about 2 0 . 8 7 per cent oxygen, a n d samples of commercial oxygen analyzed checked among themselves t o t h e hundredths of one per cent when measurements were performed accurately a n d these results checked with t h e oxygen determined by combustion over a large number of determinations. The pipette should have as much copper surface as possible ; therefore t h e copper wires should be t h i n a n d straight a n d should fill t h e entire length of t h e pipette body as otherwise t h e absorption of oxygen is not as rapid as is possible. The copper wires should be very clean a n d bright before putting t h e m into t h e pipette a n d t h e last bulb of t h e pipette should have a little of the ammonium chloride solution in i t also. The copper going into solution b y chemical change seems t o be precipitated back onto t h e metallic copper as t h e metal, t o some extent. When making a n absorption of oxygen b y copper it should be remembered t h a t t h e absorption takes place on t h e moist surface of t h e copper; consequently t h e aim should be t o wash gently over t h e copper with t h e ammonium chloride solution so t h a t t h e blue compound is dissolved, giving a fresh 1
THISJOURNAL, 7
(1915), 587
233
copper surface, a n d not t o shake t h e pipette t o have t h e liquid absorb t h e oxygen. When using a mercury burette care should be taken t h s t no mercury comes in contact with t h e copper surface as i t readily amalgamates a t t h e surface of t h e copper. The salts of mercury also precipitate on t h e surface of t h e copper as metallic mercury a n d this spoils t h e pipette. APPLICATION O F THE METHOD T O ANALYSIS
Exactly I O O cc. of t h e sample of gas t o be analyzed are drawn into t h e water burette. The capillary i s then washed by turning cock G, and t o seal t h e gas in t h e burette, acidulated water is then allowed to completely fill all of t h e capillaries and t r a p I up t o t h e edge of t h e cock K. The potash pipette is then connected t o t h e capillary E , and t h e gas in t h e burette aspirated back and forth three times. This procedure removes all of t h e carbon dioxide. The residue is measured and t h e reading recorded. The difference between I O O cc. a n d this reading gives t h e per cent of carbon dioxide present in t h e sample. The potash pipette is disconnected, t h e capillary washed, t h e gas in the burette p u t under slight pressure, t h e t h u m b is placed on t h e end of capillary E, cock D is opened and t h e water in t h e capillary allowed t o run almost t o t h e end of E. Cock D is then closed a n d t h e fuming sulfuric acid pipette attached t o E. Not more t h a n 0 . 0 2 cc. of air should be introduced at this point, if t h e pinching u p of t h e sulfuric acid in t h e pipette capillary a n d t h e connection is made carefully. The gas is aspirated back and forth two times, t h e acid drawn back t o t h e same mark in capillary a n d cock D is closed. A quick, smooth pull with one hand and with t h e t h u m b and finger of t h e other h a n d pinching t h e rubber t u b e connecting pipette with E prevents t h e acid from getting into t h e rubber connection. The other t h u m b is quickly slipped over t h e end of E, preventing diffusion of t h e small amount of gas in the capillary with t h e air. Water from a wash bottle is now blown into t h e rubber connection of t h e potash pipette and this pipette quickly connected t o E , a t t h e same time withdrawing t h e thumb. T o take out the sulfuric fumes, t h e gas is passed back a n d forth four times. The reading is taken a n d recorded. The difference between this a n d t h e previous reading gives t h e per cent of illuminants (unsaturated hydrocarbons, benzene vapor, etc.). If"all of t h e illuminants are not withdrawn by two passages through t h e sulfuric pipette they should be removed b y passing through one more time. Next remove t h e oxygen with phosphorus. Allow t h e gas t o remain in contact with t h e moist phosphorus until most of the fumes disappear. The gas is then drawn into t h e burette, measured a n d t h e amount recorded. The difference between this and t h e previous reading gives t h e per cent of oxygen in t h e mixture. A gas holder is made b y connecting two 500 cc. aspirator bottles with rubber tubing, which is wired on. A I-hole rounded rubber stopper is fitted t o
234
T H E J O C R L V A L O F ILYDC'STRIAL A N D E N G I N E E R I Y G C H E M I S T R Y
the neck of one of t h e aspirator bottles and a piece of capillary glass tubing inserted. The end of this capillary is then closed with a piece of rubber tubing a n d a pinch-cock just as t h e pipettes for t h e reagents. Enough acidulated water (distilled) is added t o this holder t o completely displace t h e air in t h e bottle having the capillary. The other bottle is fitted with a t u b e and rubber stopper t o blow t h e water, out of the capillary. The rubber stopper for t h e capillary bottle should be rounded into a n inverted basin-like depression so t h a t the air may be quickly and completely displaced. This is done by heating a heavy copper wire t o redness a n d moulding t h e stopper t o t h e proper shape. The stopper is then rather soft and unfit for use, but it should be hardened by immersing i t in a little fuming sulfuric acid. The residue of gas left after determining t h e oxygen is transferred t o this holder, a measured excess of oxygen is then added by opening cock F and allowing t h e oxygen t o flow into the wat,er burette. After measuring, t h e oxygen is transferred t o t h e holder a n d the entire gaseous mixture shaken, a t t h e same time pinching t h e rubber connection between t h e t i v o aspirator bottles to prevent air from entering or gas from leaving t h e holder. Mercury might be used in this holder having a very slight amount of acidulated water on its surface. After thoroughly mixing t h e gas a n d oxygen, I O O cc. of t h e mixture or a close approximation t o I O O cc. are drawn into t h e water burette and t h e amount accurately measured. The mercury burette is then adjusted so as t o contain I: or 20 cc. of air. Water fills all of t h e capillaries, including t h e t r a p I up t o cock K. A 2 5 0 cc. aspirator bottle can be made a part of burette B, using a small rubber stopper, then t h e entire mixture may be burned instead of I O O cc. in one operation. After recording all of t h e measurements t h e water in t h e t r a p I is forced into t h e water burette by putting t h e measured am0un.t of air in t h e mercury burette under pressure and opening cocks D a n d K so t h a t t h e flow is into t h e water burette. As soon as t h e water reaches the orifice HI cock D is closed, t h e mercury in t h e burette leveled, and cock S closed. Cock K is kept open, The burner heating t h e platinum capillary is then lighted. It should give a flame hot enough t o melt t o a globule the end of a piece of copper wire I mm. in diameter in 5 to 8 seconds. A Bausch and Lomb high temperature burner or a X'lkker burner should be used. After t h e platinum tube becomes heated t o a bright red, D is opened, t h e aspirator bottle on t h e water burette is raised slowly s o t h a t t h e water remaining in t h e capillaries is not forced through t h e heated tube, a n d then p u t on t h e high shelf. The small amount of water, not more t h a n 0 .I CC., which is forced into t h e t r a p , prevents t h e explosion of the mixture of gases from traveling back into t h e burette, which, if it should occur, would wreck t h e apparatus.
YO]. 8, S o . 3
Cock S is now slightly opened and the explosive mixture of gases allowed t o bubble through the water in t r a p I at a moderate rate a n d as soon as all of t h e gas has passed through t h e water seal, t h e water is allowed t o rise until t h e beginning of t h e heated portion of t h e tube is reached. Cock N should be closed as soon as water flows through t h e orifice HI. Cock D should next be closed when t h e heated portion of t h e combustion t u b e is reached. The heating is then stopped and water thrown on t h e hot tube from a wash bottle t o cool the tube rapidly. Cock D is opened and t h e water allowed t o come t o t h e edge of cock K , which is then closed. This residue of gas, after combustion, is measured and the amount recorded. The potash pipette is now connected t o E1 a n d the gas aspirated back and forth four times. The amount of gas left is measured and recorded and t h e pipette disconnected. The pressure on t h e gas is now slightly decreased a n d T cc. of acidulated water drawn into t h e mercury burette. This is done t o prevent mercury from fouling t h e copper in t h e copper pipette. The copper pipette is connected t o E and t h e residue of gas completely transferred thereto. I n order t o absorb oxygen completely in this step it is not necessary t o disconnect t h e copper pipette t o shake it. I t is only necessary t o see t h a t t h e copper wires have a clean coppery color by washing over them a time or so gently with t h e solution in the pipette. As soon as t h e clean copper color is seen t h e oxygen is completely absorbed, t h e absorption being very rapid. ilfter drawing t h e residue of gas into t h e burette, it is measured, then passed into a dilute solution of sulfuric acid t o see whether a n y ammonia fumes are taken out. This last residue is then measured and t h e amount recorded. I t is necessary t o heat t h e platinum combustion tube t o t h e degree mentioned, as otherwise t h e paraffins will .not be completely decomposed. Mercury should not be run into or through t h e combustion tube. The burettes should be calibrated and t h e proper meniscus used. One passage through t h e properly heated tube decomposes all of t h e gases quantitatively. Cock K a n d burette B should be thoroughly washed out with acidulated water by opening S and drawing through I part of sulfuric acid to 4 parts water. Cock K is completely revolved several times while drawing t h e acidulated water into t h e burette. The formula used for calculating t h e combustion results is easily remembered. Representing t h e oxygen used in t h e chemical combination by 02,t h e contraction by C, we have:
Hz
= C-0
CH4 =
2
3 0 2- (C
+ COz formed) 3
CO = C O z formed minus CHI The nitrogen is found by difference. I t can also be calculated by t h e residual nitrogen. Both methods give t h e same results. When a part of t h e mixture of gas and oxygen is
T H E JOURhTAL O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Mar., 1916
taken for combustion as directed above, a proportion must be made between t h e amount of t h e mixture used for combustion a n d t h e total amount on hand. The following example taken from practice illustrates the method of writing down t h e measurements and making t h e computations. ANALYSESBY H. L. DAHM Sample of water gas July 3, 1915 Burette reading cc. 5.4 coz 20.2 C,H,11
CHI =
co
. ......... T o t a l mixture., . . . . , . . . . . . . , . . , , . . . . . Amount of mixture taken for combustion., , . , ,,,, , ,,
coz - CHI
+
COz) Nitrogen is figured by difference
Should we use these formulae, t h e figures of t h e previous water gas analysis would appear as follows: Burette reading
Per cent 5.4 14.8
Residue of g a s . . . , . . . Impure oxygen added. Total mixture
..
302- C 3
HZ = C - (Oz
Residue of gas for combustion. , , , Amount of oxygen t a k e n . . . . . . ,
=
79.2 cc. 77.2 cc.
100.00
156.4 cc.
100 . O O cc.
5 3 . 6 cc. reading after combustion -15 .O cc air in mercury burette
3 8 . 6 cc. measurement of the residue of the 100 cc. of gas taken for combustion 100.00 cc. taken for combustion -38.6 cc. residue after combustion
23 5
coz
5.4 20.2 20.8
Illuminants
-
0 2
79.2 cc. 77.2 cc.
CH4 CO
Per cent 5.4 14.8 0.6 17.86 25.94
1 5 6 . 4 ~ ~ . Hz N
31.55 3.85
___
100,00 5 3 . 6 cc. -25.6 cc. 2 8 . 0 cc. 100.0 cc. 1 5 . 0 cc.
+
residue after combustion residue after using potash COz formed in 100 cc. of mixture o! mixture taken for combustion air
115.0 cc. -25.6 cc. residue after using potash
-
8 9 . 4 cc. total contraction for 100 cc. 25.6 cc. residue after using potash -15 .O cc. residue after using Cu pipette
~
6 1 . 4 cc. contraction for 100 cc. of the mixture 5 3 . 6 cc. reading of gas after combustion plus the 15 .O cc. of air -25.6 cc. reading of residue after using potash pipette 2 8 . 0 cc. equals the COz formed in 100 cc. of t h e mixture 2 5 . 6 cc. reading after using potash pipette -15.0 CC. reading after using copper pipette 1 0 . 6 cc. of 02 left which did not take part in the combustion. This amount also contains t h e oxygen in 15.0 cc.
of air used
10.6 3.1
-
amount of 02 in 1 5 . 0 cc. air
7 . 5 cc. equals the oxygen not taking p a r t in the chemical combustion of 100 cc. Compute the contraction, the carbon dioxide formed, and t h e excess oxygen for the 156.4 cc. of the mixture, t o get the proper figures for t h e entire mixture, b y using the proportions 156.4 : 100.0 cc. 156.4 6 1 . 4 X Innn = 9 6 . 0 3 , contraction for total gas 156.4 2 8 . 0 X __ = 4 3 . 8 , C o t for total gas 100.0 7.5 x = 1I .73, excess oxygen for total gas I"U.U 77.2 cc. of commercial oxygen is added t o the 79.2 cc. gas for combustion. This oxygen contains 1 . 3 per cent nitrogen. 77.2 X 0.013 = 1 . 0 cc. of nitrogen in 77.2 cc. 0 2 1 . O cc. nitrogen
1 0 . 6 cc. unused oxygen plus oxygen in 1 5 . 0 cc. air oxygen in 15.0 cc. air.
- 3 . 1 cc.
7 . 5 cc. unused oxygen in 100 cc. of mixture 2 8 . 0 X 1.564 = 43.80 = total COr = COz 8 9 . 4 X 1 , 5 6 4 = 139.82 = total contraction = C 7 . 5 X 1.564 = 11.73 = total unused oxygen 77.2 cc. = impure oxygen added - 1 , O cc. N Z = 1 , 3 per cent nitrogen in impure oxygen -1
76.2 cc. = pure oxygen added 1 . 7 3 cc. unused oxygen 64.47 cc. = used oxygen = 0 2 CHa = = 64.47 X 3 = 193.41 -139.82
__-
---."
CO = COz - CHI = 43.80 -17.86
+:
Hz = C
-
76.2 cc. pure oxygen added -1 1 . 7 3 cc. excess oxveen. left after combustion .I
64.47 cc. equals the oxygen used t o combine chemically with the gas 96.03 64.47 (oxygen used) = 31.56 per cent hydrogen 3 X 64.47 (oxygen used) = 193.41 minus 96.03 4 3 . 8 (Con formed) = -139.83
-
+
j3.58 = 17.86 per cent CH4 3 4 3 . 8 (COz formed) - 17.86 (CH4) = 25.94 per cent CO. Nitrogen is found b y computing as follows: In t h e 15.0 cc. of air used we have 1 1 . 9 cc. Nz. T h e residue of nitrogen after burning the 100.0 cc. of the mixture plus the nitrogen of the air after taking out all the oxygen equals 15.0 cc. 1 5 . 0 cc. -1 1 . 9 cc. A-z in the air used 3 . 1 cc. Nz in 100 cc. of mixture In total mixture 156.4 we will have 3' ______ 1 5 6 ' 4 = 4 . 8 4 cc. Nx due t o the nitrogen in the original gas 100 plus the nitrogen in the commercial oxygen used. I n this case t h e nitrogen as calculated previously equals 1 .O cc. in the commercial oxygen added 4.84 -1.0 3 . 8 4 cc., amount of nitrogen in the original gas
When it is desirable t o measure t h e total contraction-that is, t h e contraction due t o t h e formation of COz-the following formulae may be the HzO used: Representing t h e total contraction by C a n d t h e oxygen used in t h e chemical combination of t h e gases by 0 2 we have:
+
- (0 +
= 53.59 3
17.86 per cent CHI
25.94 per cent CO COS) = 64.47 139.82 4-43.80 -108.27
- 108.27
31.55 per cent Hz
Using this method, a complete analysis can be made in twenty minutes, as I have repeatedly made a n analysis in this time. A convenient way of cleaning phosphorus is by adding a 3 per cent solution of hydrogen peroxide, if possible free from acetanilide, t o t h e pipette and allowing it to remain until phosphorus assumes t h e yellow waxy color. When t h e ethane is t o be estimated t h e hydrogen is absorbed in a colloidal palladium solution or in a palladium tube as directed in G. Lunge's (1914) '' Technical Gas Analysis." Another wash bottle containing pure water is a t tached t o t h e apparatus along t h e side of the wash bottle containing t h e dilute hydrochloric acid. After absorbing t h e hydrogen t h e residue consisting of carbon monoxide, methane, ethane and nitrogen is transferred t o t h e gas holder and excess of oxygen added and t h e gases burned as before. T h e theoretical formulae for calculating t h e constituents of t h e mixture, when 02 equals t h e oxygen used in t h e chemical action, C equals t h e observed contraction, a n d COz equals t h e observed carbon dioxide formed, are
T H E JOURNAL OF IhrDVSTRIAL A N D ENGINEERING CHEMISTRY
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I t is usually necessary t o remove t h e carbon monoxide before t h e absorption of hydrogen. The mercury can be cleaned by putting i t into a two or three liter bottle with some dilute nitric acid and shaking it until t h e mercury is finally divided. Repeat this operation with pure water. When mercury is used in burette B, a glass cock exactly t h e same as is used a t t h e bottom of burette B1 is attached to B. The mercury surface should be leveled at t h e lowest part of t h e meniscus showing as a sort of bright line. Burrell and Seibert in Bureau of iilines Technical Paper 54 (1913)again call attention t o certain cases of gas analysis where corrections in calculating results are t o be made due t o certain of t h e gases not obeying t h e ideal gas laws. Below is a new easier method of calculating corrected results a n d proven b y simple stoichiometry t o give at least as accurate results as t h e method given in Burrell and Seibert’s paper. When carbon monoxide, methane a n d ethane are estimated together, and t h e factors for t h e partial pressures of t h e carbon dioxide formed for each constituent are used, as is necessary in Burrell and Seibert’s calculation, the sum of all of t h e separate parts of corrected carbon dioxide does not equal t h e total corrected carbon dioxide calculated by dividing t h e total measured carbon dioxide by its partial pressure factor. Theoretically, according t o Avogadro’s hypothesis a n d Gay-Lussac’s law, etc., t h e molecules in one volume of methane combine with t h e molecules in two volumes of oxygen t o form t h e molecules in one volume of carbon dioxide a n d t h e molecules in two volumes of water vapor. This water vapor should condense at t h e ordinary temperature a n d pressure if t h e original gases were saturated with moisture. Therefore, 1000 cc. of methane should combine with 2000 cc. of oxygen t o form 1000 cc. of carbon dioxide. By observation i t had been found t h a t t h e number of molecules in 1000 cc. of methane combine with t h e molecules in
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-5 cc.
of oxygen t o form t h e mole-
999 995 cules in 99j - cc. of carbon dioxide a t t h e ordinary 999 temperature a n d pressure. If this amount of carbon dioxide is corrected by dividing by t h e quotient obtained by dividing t h e theoretical b y t h e observed specific gravity of carbon dioxide a t 20’ and 760 mm., t h e corrected amount
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and if this last amount is multiplied by the quotient of the theoretical, divided by t h e observed gravity of methane, as shown in Burrell and Seibert’s paper, t h e product will be the actual amount of methane measured. Nom ii the methane is t o be calculated from t h e contraction the measured amount of methane must be divided by its pressure factor and the carbon dioxide formed also must be corrected in the same way. Divide t h e corrected contraction by 2 and t h e quotient will be t h e ideal volume of methane. Multiply this quotient by t h e pressure factor for methane a n d t h e product equals t h e measured volume of methane. This method of reasoning can be extended to more complicated formulae. Therefore, if t h e original amount of gas present as measured or calculated from the theoretical formulae be divided by the factors for t h e separate gases a n d t h e measured volume increased by the difference between t h e calculated amount and the measured amount, also if t h e carbon dioxide as measured is corrected by dividing by its pressure factor, t h e ideal quantities of all of t h e gases present can be calculated by t h e usual theoretical formulae by using t h e corrected values for t h e contractions and t h e carbon dioxide. An oil gas gave these combustion measurements: C = 130.69cc., O 2 = 117.78cc., COS = jj.5 1 cc. By t h e usual theoretical formulae t h e methane equals 5 j . 7 1 per cent, t h e carbon monoxide - 0 . 2 0 per cent, t h e hydrogen equals 12.91per cent, and t h e nitrogen equals 0.28 per cent. The total was 68.7 per cent of t h e original I O O cc. taken for analysis. The carbon dioxide partial pressure equaled 5 0 . 3 per cent a n d t h e partial pressure of t h e methane was 84.7 per cent. From Burrell and Seibert’s paper t h e molecular volume factoy for the carbon dioxide is 0.99717 and for methane 0.9991j. Divide j j . j I CC. by 0,99717;t h e quotient, 5j.668,is the corrected volume of carbon dioxide. Divide 55.71 cc., t h e calculated amount of methane, by 0.99915;the quotient, j j . 758 cc., is t h e corrected volume of CH4 if 55.71 cc. was t h e measured volume of methane. This is not t h e case here; t h e idea is t o get t h e increase of t h e corrected over t h e theoretically calculated methane; add this difference t o t h e total volume of gas for combustion in order t o arrive at t h e corrected figures for t h e contraction. This difference is 0 . 0 4 8 and can be added t o t h e uncorrected contraction provided the difference between t h e corrected and measured carbon dioxide is subtracted, as this last difference is 0 . I j 8 cc., the corrected contraction is 130.58cc. The corrected carbon dioxide is jg .668 cc. The oxygen used is I 17.78CC. By t h e ordinary theoretical formulae t h e calculations are completed and give t h e following values: Methane Hydrogen Nitrogen
5 5 . 6 per cent 1 2 . 8 per cent 0 . 3 per cent
From the foregoing deductions, t h e molecular volume factors a n d t h e specific gravity of t h e pure cc. will equal t h e ideal amount of methane IOOIL gases can be determined by t h e ordinary combustion 999
Mar., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
method a s described in this paper provided pure gases can he obtained as directed in Bureau of Mines Technicd Paper, 104 ( 1 9 1 5 ) by Burrell, Seibert and Robertson. For accurate work in these determinations larger measuring instruments should be used.
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volume of the hydrogen peroxide solution and nitric acid in the same manner. The difference between thenumber of cc. of potassium permanganate solution required for t h e blank titration and the number of cc. required for the red lead titration is the amount required for the hydrogen peroxidc 34.2 34.1
A W I D METHOD FOR THE ANALYSIS OF RED LEAD AND ORANGE MINERAL BY
JOXN A. S C ~ Z A ~ F F Z R Received AYPYL4. 1915
34.0 33.9 33.8
In estimating t h e chemical value of red lead and orange mineral, i t is essential t h a t the true red lead, 3 3 . 5 Pb,O,, content or the lead dioxide, PbOl, content be 33.4 determined. Where a large consumption of these 3 3 . 3 products or their purchase on specifications necessitates 33.2 a determination of these constituents a t d l times t h e 33.1 methods in use a t present are rather long and involved. The following method has been perfected for this 32.8 analysis and gives accurate results in a most rapid 3 2 . 7 inn.on manner. The method depends upon t h e initial decomposition 9 9 . 6 9 99.38 of t h e true red lead, PbaO,, with nitric acid, according 99.07 t o t h e following reaction:' 98.77 PbaOd 4HNOa = zPb(NO& H10 HQPbOa. 98.46 The H2Pb03 or PbOa is then decomposed with hydrogen 98.16 peroxide as follows:2 97.85 Pb02 HlOz = PbO H20 On. 97.55 The excess of standard hydrogen peroxide used is then 97.24 titrated with a standard potassium permanganate c 96.94 solution. 96.63 I n carrying out the analysis, one gram of t h e red, 96.32 lead or orange mineral is treated with 1 5 cc. of nitric 96.01 acid, having a specific gravity of 1 . 2 . The mixture 95.71 is then stirred until t h e first reaction given is complete, 95 40 as is evidenced by a n entire disappearance of all red color. There is then added from a calibrated burette or pipette exactly IO cc. of dilute hydrogen peroxide, made u p of a mixture of I part of 3 per cent hydrogen 94.49 peroxide solution t o 3.5 parts of water. It has been 9 4 . 1 8 found t h a t a I O cc. automatic pipette, with a three9 3 , R8 way stop-cock, is excellent for delivering a definite 93.57 volume of hydrogen peroxide solution a t all times. 93.26 After the addition of t h e hydrogen peroxide solu92.96 tion, the resultant mixture is stirred until almost 92.66 complete decomposition of t h e lead peroxide has been 92.35 effected, a s shown by the second reaction. The 92.04 decomposition is completed by t h e addition of a little 9 1 . 7 4 hot water and stirring. The contents of t h e beaker, 91.43 after complete decomposition and solution of t h e lead peroxide, are diluted with hot water t o about 2 5 0 cc. no. I volume and titrated directly with a standard potassium permanganate solution having an iron value of o.oo5. necessary for the complete decomposition of the lead The solution is titrated t o a faint pink permanganate Peroxide. This difference multiplicd hy 3 . o j 8 givcs t h e percentage of red lead according t o the following color. proportion: A blank titration is then made on exactly t h e same aFe : PbrOl = 0.005 : X, or, 1 1 2 : 6 8 j = 0.005 : X I Treadwell and Hall. "Analyfieal Cbemirtry,'' Vol. 11, p. 623. ' [ b i d . . Vol. I. p. 53. whence, X = 3.058.
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