260
T H E J O U R N A L OF 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
volume of gas aspirated through t h e apparatus a n d determined by noting when t h e water in F had reached a mark showing t h a t volume t o have passed over. The tube A is then withdrawn from t h e furnace and, while still attached t o B , a further volume of 1000 cc. of air aspirated. This was found sufficient t o remove completely t h e last trace of SO2 from all parts of t h e apparatus in front of D . A is then disconnected, t h e outside wiped off with a cloth or damp sponge, and t h e inside thoroughly washed down into a small beaker with distilled water. This point is very important, for it was found t h a t in many cases approximately j o per cent of t h e SO3 had condensed and been retained in A . The contents of B are next added t o the washings from A and this t u b e also thoroughly washed out. The two funnels carrying the filters are then disconnected, t h e filter papers placed in t h e beaker containing t h e washings from A and B , and t h e funnel
VOI.
a,
NO.
of t h e aspirated gases is sufficiently high, appreciable amounts of SO2 are oxidized t o SO, on contact with t h e hot dust and walls of t h e tube. If, then, t h e gases be drawn through slowly this will introduce large errors. I n a number of instances when t h e gases were aspirated from t h e hottest hearths of t h e roasting furnaces, t h e temperature being between 600' C. and 700' C., t h e ratio of SO1 t o SO? found was I : I O when t h e aspiration rate was 300 cc. per minute, while when t h e gases were drawn through a t 4 j cc. per minute the ratio was I : 6. With a n aspiration of approximately 1000 cc. per second, obtained by allowing the gases t o rush into a partially exhausted z liter bottle and then drawing this gas t h r o u g h ' t h e apparatus, the ratio of SO3 t o SO? was I : 1 2 . With a temperature less t h a n 450' C. this catalytic action is very slight and can probably be neglected, but with hotter gases it is necessary either to aspirate with sufficient rapidity or to cool t h e sampling tube by means of a water jacket. TABLE I-TIPICAL ANALYSES0~ P ~ u nGASPO= SO8 AND SO3 Temperature of flue gases in each case averaged ahouf 400' C. Volume of gas taken, 2000 CC. Pressure, 655 mm.
.....
To...
--
pers- Aspirafure in tion Cc. N/IOarpira- time NaaCOz for fion Minbottle ,,fer so. so, sn 5 5.4 78.4 60 s 3 . 5 50.1 38 20 4.1 67.8 49 is 4.15 4n.o
Gram found
soI
so,
0 . 0 2 1 6 0.2508 o.ni*00.16.w 0.01640.2l70 0.0166 o . i m
Volume Percent
Ratio of
so1 so1 snItosoI 5.82 0.284.05 0.305.02 0.32 3.70 0.40
i : 14.55
1:14.45 1:16.73 I : 11.56
Table I shows analyses of gases taken from t h e outlet flue of a multiple hearth roasting furnace which are typical of a large number in which t h e method here described was employed. LABORATORIES WBSTBRN PFCECIPITATION CoarPrNu
Los ANOBLBS.CALIPORNIA
PIO.
I
BOILING AND CONDENSING POINTS OF ALCOHOLWATER MIXTURES' B y P. N. EVANS Received December 22. 1915
&OB. E. F-Syphon
aspirating bottles holding about 3 literr each &Pinch-cork t o regulate Bow of syphon w s t ~ r . H-ThermOmete..
which has been next t o B also washed and t h e washings added t o t h e same beaker. A drop of methyl orange is added t o t h e contents of the beaker a n d t h e H2SOI present titrated with N / I O Na2CO3. T o determine t h e SO* caught, methyl orange is added t o D and t h e excess of Na2C03 determined by titration with N / I O HCI. The volume of t h e N l r o NalC03 used u p during t h e aspiration of t h e gases is a measure of t h e amount of SO1 present. It was found by repeated trials t h a t t h e one absorption bottle D was sufficient t o retain all 'SO2 even when t h e gases were aspirated a t t h e rate of 2 0 0 0 cc. in 4 minutes. An important source of error in determinations of this kind is t h e catalytic action of t h e walls of the sampling t u b e and also of dust particles which may collect in t h e tube. When t h e temperature
The boiling points of alcohol-water mixtures depend on the proportions of the constituents, a n d range from about 78" C. for pure ethyl alcohol t o 100' C. for pure water. Except a t a concentration of 96 per cent alcohol by weight (97.5 per cent by volume) any mixture of alcohol and water when boiled gives off a vapor of different composition from t h a t of t h e liquid, t h e vapor being richer or poorer in alcohol than t h e liquid when the latter contains respectively less or more t h a n about 96 per cent of alcohol. The vapor has, of course, a condensing point identical with the true boiling point of t h e liquid from which i t is given off. The purpose of t h e work here reported was t o ascertain experimentally t h e relation between the boiling point (or condensing point) a n d t h e composition of both the liquid and vapor phases, t h a t with the information so obtained it might be possible by observation of t h e corrected boiling point t o learn t h e comI
1913,
Abstracted b y author from Indiana Academy of Science Report for
'
Mar., 1916
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
261
position of t h e boiling liquid a n d t h a t of t h e vapor stated. The average of t h e percentages found in t h e liquid in t h e flask before and after distillation being evolved at any moment during distillation. The relation between t h e boiling point and t h e com- was taken as t h a t of t h e liquid phase, and t h e perposition of t h e liquid phase was determined for low centage in the distillate as represented in t h e vapor percentages of alcohol by J. J. Poh1,l and for all con- phase a t t h e time when t h e boiling point was observed centrations by Dupr6 a n d Page,* a n d b y G r ~ n i n g , ~half-way through the distillation. The original volume of t h e liquid in t h e flask was b u t t h e results were very discordant. H. W. Wiley4 gives a rule for calculating the strength of alcohol- restored by t h e addition of 1 5 cc. of water, a n d the water mixtures containing not over 5 per cent of alco- slightly more dilute mixture so obtained was used hol. W.’ A . Noyes and R. R. Warfe16 determined for t h e next experiment. I n this way 43 mixtures t h e relation between boiling point a n d composition were examined, ranging from 9 1 to o per cent alcoover t h e whole range, with special reference t o t h e hol. Corrections were introduced in t h e temperature minimum boiling point, which they found t o be 78.74’ C. for 96 per cent alcohol by weight, a n d mention is readings for t h e barometric pressure a n d for t h e exmade by t h e m of t h e determination by J. K. Haywood6 posed mercury column, as follows: Regnault and of boiling points of mixtures containing less t h a n 8 5 Claassenl have shown t h a t the effect of such variations per cent of alcohol. So far as known t o t h e writer of pressure as may be due t o atmospheric conditions t h e relation between t h e composition and condensing is practically t h e same on t h e boiling point of water
point of t h e v a p o y phase has not been previously determined. PROCEDURE
The gravity and temperature of a strong alcohol were determined with a Westphal balance and t h e weight per cent of alcohol calculated b y means of Mendelejeff’s table.’ Five hundred cubic centimeters were placed in a one liter distilling flask with a n accurate thermometer graduated in tenths of a degree inserted with its bulb just below the side-neck. The liquid was then slowly distilled at a uniform rate of about one drop per second until 1 5 cc. had passed over, the distilling temperature being read when 7 j cc. h a d collected in the graduated receiver. The per cent of alcohol in t h e distillate and t h a t in t h e residue were determined from t h e gravities as already 1 2
Jahresbev., 1860, p. 455. Phil. Tvans.. 1869, p . 591.
Watts’ “Dict. Chem.,” 1872, I, p . 95. Jour. Am. Chem. Soc., 18 (1896), 1063. 6 Ibid., 23 (1901). 463. e J . Phys. Chem., 3 (1899). 318. 7 Biedermann’s “Chem. Kal.,” 1914, I, p. 296.
a n d t h a t of alcohol, so it seemed justifiable t o use Landolt’s correction for these mixtures and a d d 0,043 t o t h e observed reading for each millimeter below 760 shown by t h e barometer. The observed temperat u r e reading was also corrected for the exposed mercury column by adding N ( T - t ) 0.0001j 4 , in which N is the length of t h e exposed column in degrees, T t h e observed boiling point, a n d t t h e room temperature. The thermometer used was compared throughout t h e range of observations with a similar instrument calibrated b y t h e Reichsanstalt. The corrections in no case exceeded 0 . I a n d were disregarded, as only this degree of accuracy was aimed at. The temperature results are probably accurate within 0 . 2 degree, a n d the concentrations within 2 per cent (in most cases within I per cent). RESULTS
3
4
The results obtained, are given in Table I. The relations existing between t h e boiling point or con1
Biedermann’s “Chem. Kal ,” 1914, 11, pp. 112, 113.
T H E JOLTRNAL 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
262
TABLEI-VALUES o
2g
.E
OBTAINEDBY
*
E
L
0
Vol. 8, No. 3
EXPERIMENT
2g
.a
e
‘i!
P
*
P
(n) This experiment was with water only.
densing point and t h e composition of t h e liquid and vapor phases are shown clearly b y t h e plot in Fig. I. A convenient table of results estimated from t h e curves appears in Table 11, which enables one t o determine quickly t h e approximate concentration of any alcoholwater mixture b y observation of its boiling point, with corrections for barometric pressure and exposed mercury column. I t is also possible t o tell t h e approximate composition of both liquid and vapor (or distillate) a t a n y moment during the distillation of a TABLE 11-VALUES ESTIMATED FROM CURVESIN FIG. I Boiling point O C .
78.2 78,4 78.6 z8,8 19.0 79.2
Weight a,cobol per cent in
Boiling point
liquid vapor 92 91 89 85 82 88 80 78 86 76 85
82.0 82,5 83.0 83,5 84.0 84.5
7 79 9 .. 4 6
74 72
80.4 80.6
62 59 56 53 50 47 45
81.8
43
Boiling point
liquid vapor 79 41 78 36 33 78 3o 77 27 76 25 75
91.5 92.0 92.5 93,0 93.5 94.0
O C .
Weight alcohol per cent in liquidvapor 8 55 8 53 7 51 49 5
6
46 44
85 84
8 85 5 .. 05
23 21
74 73
94 9 5 .. 50
54
42 39
82 82 81 81 80
87.0 87.5 88.0 88.5 89.0 89.5
17 16
1
23 19
I 0
10
91.0
97.5 98.0 98.5 99.0 99,5 100.O
2
80 80 79
70 69 68 67 65 63 61 59 5;
i::: 264: i i 80.2 83 80.8 81.0 81.2 81,4
O C .
Weight alcohol per cent in
:::: ;t if 15
13 12 11 lo 9
;;:; 2 i;2: 1s
mixture. The accuracy is, of course, less t h a n by the usual and more difficult analytical method of distillation and t h e determination of the gravity of the distillate with a pycnometer. PURDUEUNIVERSITY LAFAYETTE INDIAXA
A RAPID PYCNOMETRIC METHOD FOR “GRAVITY SOLIDS” IN CANE-SUGAR FACTORIES By HERBERTS. WALKGR Received September 13, 1915
Since t h e introduction into sugar factory control b y Deerr’ of t h e terms “gravity p u r i t y ” and “gravity solids,” and his demonstration t h a t the determination of total solids b y t h e Brix spindle, while not absolutely accurate except in pure sucrose solutions, when applied t o juices, sugars, and molasses a t approximately the same dilution (about I j ” Brix) yielded, in consequence of consistent error, results fully as valuable for factory control work as the more tedious process of drying t o more or less constant weight, this latter method has been entirely abandoned in many factories. T h e principal objection t o t h e substitution of densimetric for direct drying methods has been t h e lack of e\Ten relative accuracy in Brix spindle readings; this: as regards accuracy of reading t h e graduations on the stem of t h e spindle, has been somewhat improved b y several devices suggested in recent years, but there still remain certain inherent errors in the method, due t o variable viscosity and surface tension of liquids, which are very difficult t o eliminate. The pycnometer is generally conceded t o be an exceedingly accurate means of determining specific gravities, b u t has thus far found little favor in cane1
Bull. 41, Agr. a n d Chem. Series, H. S . P. A. Expt. Station.
