paratus is only a modification of t h a t of Sy, b u t it is probably easier t o construct. The products of t h e digestion remaining in t h e flask a t t h e end of t h e operation will thus ha.\-e come in contact with nothing b u t glass. X slow stream of air drawn through t h e bottle serves t o prevent the escape of a n y fumes from t h e digestion flasks into t h e air of the laboratory. It may be t h a t the slightly increased pressure under which M r . Merkle conducted his determinations hastens appreciably the completion of the digestion. I can only say t h a t with t h e apparatus here described foaming has never been a source of inconvenience. LABOR.4TORY
STATE
DEPARTMENT OF HEALTH hfARYLXND
BALTIMORE,
t h e present, attention is called t o the three series of lines drawn a t angles whose tangents, according t o t h e scale chosen, are 44, 3 2 and 28. Suppose t h a t t h e gas analyzed consists of a mixture of COS, O?.OS, CO, N1, CH4, CZI-L, and Hn. Such a mixture includes the large majority of cases which come before t h e engineer. The The The The
molecular molecular molecular molecular
weight weight weight weight
of of of of
COS is 44 CO, H or CzHr is 28 Oz is 32 CHa is 16
T o obtain X multiply the volumetric proportion of hydrogen b y 2 . Finding this value on t h e righthand A scale. the approximate position between two of t h e lines sloping at a n angle of tan-' 3 2 can be judged and maintained while these lines are followed is reached on the until the value of (I,'sCH~ 02) horizontal scale. Proceeding horizontally from there t o the left-hand 4 scale thus gives t h e value. on t h a t scale, of 2H2 16CH4 3 2 0 2 . From this point following t h e lines a t t h e angle tan-' 28 until t h e value of CO X2 C2H4 is reached on the horizontal scale gives t h e value of 2H2 16CH4 3202 z8(Co Nz C2H4) on the left-hand scale -4. Lastly, from this point proceeding along the lines a t the angle tan-l 44 until t h e value of COS is reached on the horizontal scale, the value of X is obtained on t h e vertical scales A. The whole operation can, of course, be carried out much more quickly t h a n it can be described. The accuracy obtainable x i t h the diagram given is well within 1 per cent. Thus, if the analysis of the supply and exhaust gases f r o m a gas engine is obtained, the weight of air per pound of supply gas is given b y
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SIMPLIFICATION O F GAS ANALYSIS CALCULATION By WILLIAMJ. WALKER Received March 15, 1916
The following note is a n a.ttempt t o simplify existing methods of estimating t h e various quantities involved in engineering gas analysis calculations. These are met with in flue gas analysis. gas engine supply and exhaust gas analysis and in dealing with gas producer reactions and tests. I n gas analyses all quantities are stated in terms of proportion b y volume and t h e first operation generally necessary is t o reduce these t o proportion b y weight. This is obtained b y the use of the formula Proportion by weight of t h e constituent A in t h e gas mixture
1
aA = & +-bB + =-+-2D?tC_
where A, B, C ,etc., = proportion by volume of each constituent in the gases and a , b , c, etc., = molecular weights. Thus if in a gas engine exhaust analysis the constituents COe, O2 and S Z only are presen't then
+ + + + +
{
Proportion b y weight of hydrogen
+
+
1+
+
+
Proportion .b~ y -~ wt. . ~ of C in supplr gases Proportion by w t , of C in exhaust gases ~
All the quantities inrolved here can be obtained rapidly from t h e diagram. The method of procedure is evidently much better t h a n the laborious compilaand so for t h e proportion of a n y constituent. 9 1 ~ 0 , tion of quantities, each involving t h e weights per if it is desired t o obtain t h e proportion b y weight of cubic foot of the constituent gases. a n y element it is only necessary t o multiply each of Another quantity, t h e compilation of which one the constituents containing t h a t element by t h e total often sees carried out by roundabout methods. is atomic weight of the element contributed b y it towards the volume of any constituent per pound of t h e gas the molecular weight of t h e constituent. Thus, if mixture. t h e constituent gases A, B and C contain a common Thus! element x, then Volume of constituent A ) . A = 6 Proportion by weight of carbonic acid gas in the mixture
Proportion by weight of .r
1
=
aA
1
=
44
.~ ..
+ c'C +-%'A.~~*b'B b B + CC -k dD + etc.
per lb. of gas
Weight in lbs. of 1 cu. f t . of gas
0.0028X
where 0.0028 = weight in lbs. of 1/'2 cu. ft. of hydrogen where a ' , b' and c' = total atomic weights of the and A and X have t h e same signification as before. element contributed towards t h e molecular weight This is evident since the weight, per cu. ft. of a n y gas of t h e constituent containing it. equals its molecular weight multiplied b y the weight. Thus, if a producer gas consists of a mixture of C O , of half a cubic foot of hydrogen. Thus if a gas conC2H4,NB:H2 and COS, then tains 0 . 2 5 part of CO and 0 . 1 3 part of HP: t h e n Proportion by weight ] = 12(CO + COz -p2.C~H4)_T h e weight of CO A H2 ] = 0.25.+0.13 = ~0.38of carbon 44COs - 2 8 ( C O 1 .C2Hd + Nz) + 2Hz per Ib. of gas 0.0028X 0.0028 x and Proportion by weight 2(Ha T 2 C I X Column B in t h e chart gives the values of 0 . 0 0 ~ 8X:. of hydrogen 44COz - %(CO -+ C;Ha + i S z ) - 2Hz or t h e weight of one cubic foot of the gases considered. Hereafter, the symbol X will stand for t h e summation The lines drawn a t a n angle of tan-' 1 2 are for t h e of t h e series GX bB cC dD etc., for t h e purpose of obtaining the value of 1 2 ( C 0 CO, gas mixture considered. This quantity X is required CH4 zC2H4) which is required in the computation. f o r many purposes in different calculations. To obof the proportion by weight of carbon in the gases. tain it quickly and m-ith t h e minimum of calculation FAIRFIELD, VICTORIAPARK the chart s h o v n opposite has been constructed. For &f.4NCXESTER, ENGLAKD ~
~~
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July, 1916
T H E J O L7RAVALO F I N D C S T R I A L A X D E N G I N E E R I N G C I i E M I S T R Y
64 1
BCB
a
Conslitaeot tn A-MOLECULAR
WEIGHTX PROPORTION OF CONSTITCEKT
UQ~C
Vo\m, B-WEIGHT
Gas PER
CUBIC
FOOT OF
GAS
