Dec., 1913
T H E J O U R N A L O F I N D U S T R I A L A N D ENGINEERING CHEMISTRY
I
1017
LABORATORY AND PLANT
DETERMINATION O F NITROGEN BY THE NITROMETER By C. M.
JOYCE
AND
HARRYLA TOURETTE
Received October 20, 1913
The nitrometer consists of a gas generating bulb fitted a t t h e top with a two-way cock leading t o a dissolving cup and a gas exit tube, and which has at t h e bottom a connection for a rubber tube leading t o a leveling tube, t h e whole being filled with mercury to a level just below t h e upper cock; a cylindrical glass measuring t u b e graduated from 0-100 cc. connected t o a leveling t u b e through a T tube leading t o a n equilibrium tube. T h e latter is shaped like a n inverted IOO cc. pipette graduated downward below t h e bulb from 10-130 cc. The whole system is filled with mercury so t h a t t h e measuring t u b e may be completely discharged by raising t h e leveling tube. ADJUSTING
T H E EQUILIBRIUM TUBE
The volume of I O O cc. of d r y air at o o C. and 760 mm. under t h e temperature a n d barometric conditions
Holder G a s Generot
Bulb
t h e leveling tube so t h a t the level is t h e same in t h e three tubes. T h e volume of gas in the equilibrium tube is then read a n d compared with t h e calculated volume a t t h e time, a correction in t h e subsequent gas readings in the measuring t u b e being made accordingly. NITROGEN I N POTASSIUM NITRATE
Approximately 0.4 gram potassium nitrate is placed in a weighing tube, dried'two hours a t I I O ' C., desiccated 24 hours over sulfuric acid a n d weighedexactly by difference into t h e cup of t h e gas generating bulb. This is dissolved in 9 cc. 95 per cent sulfuric acid added through a siphon thistle tube, entering t h e t o p of the dissolving cup through a tight-fitting rubber stopper. When t h e salt isdissolved i t is drawn into t h e gas generating bulb and followed by two washings 1.5 cc. each of 95 per cent acid. The bulb is then shaken with a motion normaltoits long dimension until t h e volume of gas determined b y a rough paper scale pasted on t h e leveling t u b e becomes constant, this operation taking from 3 t o 5 minutes. The gas is passed into t h e measuring tube and after standing 5 minutes t h e leveling a n d measuring tubes are so adjusted t h a t t h e level in t h e equilibrium tube reads IOO cc. a n d is t h e same as t h e level in t h e measuring tube. The reading of t h e latter is then taken. As t h e temperature andbarometricconditions,in so far as they affectt h e measured volume of t h e gas, are automatically compensated by t h e equilibrium tube, a n d as t h e gas is washed with sulfuric acid a n d is, therefore, dry, t h e percentage of nitrogen may be calculated directly, correcting only for the calibration of t h e equilibrium a n d measuring tubes. Seventeen determinations made when t h e room temperature ranged from 20-28' gave 13.71 per cent nitrogen, t h e theoretical being 13.84 per cent. E F F E C T O F ROOM T E M P E R A T U R E
It was noted t h a t t h e nitrogen determinations P Clo m p
C
prevailing a t t h e time is calculated, three drops of 98 per cent sulfuric acid are drawn into t h e t u b e a n d t h e level of t h e mercury fixed in accordance with t h e calculation. T h e cock of t h e tube is t h e n closed a n d sealed with melted paraffin. The volume in this t u b e may be confirmed at a n y time b y opening t h e measuring tube a n d adjusting
I
of pyroxylin when t h e room temperature was over 30' C. appeared abnormally high. Determinations of potassium nitrate were accordingly made a t temperatures of 31-35' when t h e theoretical percentage was obtained. This would indicate t h a t t h e solubility of nitric oxide in 95 per cent sulfuric acid diminishes practically t o zero under these conditions. Nitrogen determinations of a well pulped sample of nitrocellulose were made a t room temperatures ranging from 25' t o 35' C. with t h e result t h a t t h e apparent percentage increased beginning a t 2 7 ' C., being 0.03 higher a t 2 8 O , 0 . 0 7 at 2 9 ' , 0.10 a t ~ g . 5 ' 0.13 ~ at 30°, 0.20 a t 30.5', a n d 0.23 from 31.o'to 35.0'. The results on nitrocellulose h a d been previously corrected for solubility of nitric oxide in sulfuric acid, t h e correction beingbasedon thedifferencebetweenthe found a n d calculated valuesfor potassiumnitrate. Thiscorrection amounted t o approximately 0.10per cent and would account for about half t h e differenceobservedurhennitrocellulose was determined a t t h e temperatures before cited. T h e greater apparent increase in nitrogen in pyroxylin over potassium nitrate with rise of temperature can be accounted for only by t h e partial breaking up of the cellulose into carbon monoxide and carbon dioxide.
1018
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
T h e formation of carbon dioxide has been partially investigated, t h e contents of t h e measuring t u b e from determinations made when t h e temperature was over 30' C., having been passed through a n absorption t u b e filled with barium hydrate solution. This method 3-c
Temp.
cc.
Temp.
20.0-27.5 28.0 29.0 29.5
+ O , 90
30.0 30.5 31.0-35.0
f0.74
+0.34 +0.10
Vol. 5 , No.
12
cc. -0.14 -0. io
-0.94
'
ARLINGTONCo., ARLINGTON, N. J.
LABORATORY COLUMN STILL
340
By H. K. BENSON Received September 22, 1913
Increase in P e r c e n t of
I n t h e description' of t h e equipment of t h e chemical engineering laboratory of t h e University of Washingt o n , Fig. 9 of Plate I shows t h e location of a n alcohol still. During t h e last year, through t h e kindness of a local manufacturer, a working model of a continuous column still has been installed, which has given excellent results in operation. T h e still, which is made of copper, consists essentially of a preheater, primary column a n d rectifying column. T h e general plan of construction is shown in t h e sectional drawing, Fig. I , a n d photo of t h e installation,
N i t r o g e n with T e m p e r a t u r e
J%m Suppfy
II
offers some difficulties, owing t o t h e small q u a n t i t y of carbon dioxide, t h e presence of which has been determined only qualitatively t h u s far. T h e exact measurement of this gas and t h e formation of carbon monoxide will be investigated later. Duplicate Kjeldahl determinations of t h e sample of nitrocellulose determined a t varying temperatures were 0.09 per cent below t h e figure obtained with t h e This difference nitrometer between 2 0 ' a n d 28'. is within t h e limit of error of t h e two methods. LIMITATIONS O F NITROMETER
T h e nitrometer gives results reliable within 0 . 0 2 per cent on nitrate nitrogen, using 0.4 t o 0 . j gram sample. It is not available for t h e determination of nitrogen in celluloid or other substances containing carbon ring compounds which appear t o prevent t h e complete liberation of nitric oxide in t h e presence of sulfuric acid a n d mercury. SUMMARY
Besides t h e corrections for calibration a n d standardization of t h e nitrometer in accordance with tempera t u r e a n d barometer, t h e gas readings should be corrected for solubility of nitric oxide, which diminishes when t h e temperature goes above 28' C., a n d t h e formation of other gases by t h e breaking u p of t h e cellulose molecule which increases. The following table gives t h e algebraic sum of these two corrections for temperatures ranging from z o o to 3 j ' C.:
FIG.1
Fig. 2 . It has a t o t a l cubic content of 9.24 gallons, water measure, a n d is capable of producing from 2 t o 4 proof gallons of alcohol in 8 hours. The liquid t o be distilled is fed by gravity into t h e preheater from small storage tanks. The heat is furnished in p a r t by t h e vapors from t h e primary colu m n a n d in p a r t b y radiation from water which has become hot in t h e rectifying condenser. T h u s t h e hot liquid enters t h e primary column and is discharged on t o t h e double boiling chambers where t h e volatile portions are vaporized while t h e residues pass downward through a t r a p , or automatic discharge. T h e vapors next pass into a n enclosed annular ring in t h e preheater, t h e heavier portions condense while t h e lighter pass over into t h e rectifying chamber, are subjected t o repeated condensation a n d vaporization a n d finally constitute t h e high proof alcohol. Steam is drawn from t h e heating system, passes through a superheater a n d thence i n t o a pressure 1
TITISJ O U R N A L , 4, 609 (1912).
