INDUSTRIAL AND ENGINEERING CHEMISTRY
316
TABLEI. RESULTS OF THE COMBUSTIONS
Sample
Run
Hydrogen Carbon Deviation Deviation from mean from mean Found value Found value
% Commercial propane fraction (oontains propylene)
,
1 2
3
Cracked petroleum fraction (boiling between 25' and 50' C.)
1 2
n-Heptane
1
17.64 17.68 17.65 Bv. 17.66 14.37 14.41 -4v. 14.39
% -0.02 +0.02
-0.01
....
-0.02
+o.oz
....
16.01 -0.05 2 16.09 +0.03 3 16.09 +0.03 Av. 16.06 Theoretical 16.10
.... ... .
% 82.22
82.26 82.20 82.24 84.82 84.78 84.80
Carbon-Hydrogen Ratio Deviation from mean Found value
Sum
% -0.02 f0.02
-0.04
.. . .
+0,02 -0.02
....
83.76 -0.08 83.87 +0.03 83.89 f0.05 83.84 .. 83.90 ..
.. ..
made of a very great number of low-boiling petroleum fractions without the occurrence of a single explosion. The data shown in Table I indicate that the results can be duplicated with an accuracy of about 0.05 per cent, even if rubber stoppers are used a t both ends of the combustion tube.
Glass Head for a Laboratory Water Still PAUL F. SHARP AND EARLE B. STRUBLE Cornel1 University, Ithaca, N. Y.
T
WO large Pyrex flasks, joined by a goose neck of widebore glass tubing, have been used for large-scale laboratory vacuum distillations in various laboratories for a number of years. In this laboratory two 23-liter flasks are used, one serving as the distilling flask, the other as the condenser, with the cooling water flowing over the outside. Difficulty with the repeated loosening of the tubes in the head of laboratory water stills, which permitted a trace of the cooling water to enter the stream of distilled water, led to the trial of a Pyrex flask as a stillhead. A 5-liter flask was used on a steam-heated still with a capacity of 8 liters (2 gallons) an hour. The glass stillhead was satisfactory and has been in almost daily use for about 2 years.
81
+CON DENSING WA TER
99.86 99.94 99.85 99.88
4.66 fO.01 4.65 0.00 4.65 0.00
99.19 99.19 99.19
5.90 f 0 . 0 1 5.88 -0.01 5.89
99.77 99.96 99.98 99.90
5.23 +O.Ol 5.21 -0.01 5.21 -0.01 5.22 ... . 5.21 . ..
...
..
...,
.... .
VOL. 8, NO. 4
For greater accuracy all rubber connections in Figure i should be e l h i nated and replaced with ground glassto-glass, glaes-to-copper, or quartz-toquartz joints (1). If a separate combustion tube is used for the analysis of liquids only, it is evident that, since the usual combustion boat has been the ing tube and the combustion tube may be made in one piece, thereby eliminating the rubber stopper between them' In such case the section of the combustion tube which is normally used for the boat and for the copper spiralmay be either entirely omitted or filled with copper oxide. Literature Cited
(1) Bruun, J. H . , Bur. Standards J. Research, 2, 487 (1929). (2) Reid! E. E.1 J. Am. Chem. SOc.134,1037 (1912). RECEIVED May 9, 1934. Resubmitted April 22, 1936.
A Simple Micro- and Macro-Kjeldahl Steam Distillation Apparatus J. M. FIFE U. S. Department of Agriculture, Bureau of Plant Industry Division of Sugar Plant Investigations, Riverside, Calif.
T
HE Kjeldahl distillation apparatus shown in Figure 1
possesses all the advantages of the apparatus now on the market and yet is so much simpler in design that it can be built by the average laboratory technician without difficulty and a t a comparatively low cost. By placing a steam chamber, C, between the steam g e n e r a t o r , B, and the distilling chamber, F , the s t e a m jacket and its two large ring seals are eliminated, which is the chief difficulty encountered by the ordinary laboratory technician. The distillation is carried out with all s t o p c o c k s closed. The generated FIGURE1 steam passes through the steam chamber, C, to the distilling chamber and then through the trap, G, to the cooled condenser. The water formed from the first steam which condenses in the steam chamber keeps the large 4-mm. stopcock cool and out of contact with the steam. With suction applied at I by means of the aspirator, the sample is removed and ammonia-free rinse water drawn up the condenser tube through the trap, G, and down into the distilling chamber, through the steam chamber, C, and into the sink.
l
The arrangement used is illustrated in sufficient detail to make its construction clear. The curved neck and the return of a small amount of the condensed water reduce entrainment. The transparency of the condenser permits the inspection of its operation. The condensing surface is large. The cooling water cannot enter the distilled water supply. The condenser can be readily cleaned. RBCBIVED February 17, 1936.
RECEIVED January 15, 1936.
