June,
T H E J O U R ! V A L O F I N D U S T R I A L A N D E N GIN E E RI S G C H E M I ST R Y
I9I6
center is t h e actual depth of turpentine equivalent t o a No. I yellow glass. The details a n d operations can probably be better followed from t h e diagram. I n Table I the comparative readings in the cell and in t h e tubes on five different turpentines b y two observers are given. It will be seen t h a t t h e two procedures in t h e hands of experienced operators give essentially t h e same results. This demonstrates further t h a t had irregularities existed in t h e daylight glass they had no material effect, The cell with the eyepiece has a decided advantage. however. in t h a t matchings can be made more quickly and with less effort. Table I 1 shows t h e concordance between individual readings a n d also the average of five readings on each of fifteen different turpentines, b y two observers. TABLEI1 SAMPLEOBSERVER 1 A , ,, , , , ,.., 2
B . ,, , ,. , ,.. A . ........
3
B. . . . . . . . . . A , ,,, , , ,,,.
4
B.,, A , ,,
, ,,,, ,
,
, ,,,,. B . ,, , , . , , . . ,
.A . . . . . . . . . . B . , .., , , . . , SAMPLEOBSERVER 6 A , ......... B.,........ 5
7
A. . . . . . . . . .
8
A , ,. . . . . . . .
9
-4..
B . ,. . . . . . . .
B. . . . . . . . . .
........
B.,. . . . . . . .
A , ,........ B.,........ SAMPLEOBSERVER 10
11
12 13
A , ,, , , , , , .. B.,,,,,,,..
A , ,........ B . ,........
-4. ......... B.
14 15
.........
A..........
B... . . . . . . . 4.......... B . .. . . . . . . .
IKDIVIDOAL RE.4DIKG
154 155 116 116 143 144 64 62 56 56 66 69 51 50 52 49 52 48 26 26 27 24 32 29 17 14 16 14 16 15
152 158 116 122 145 150 64 66 51
154 159 112 118 146 146 65 64 55 52
154 153 114 118 144 144 65 66 54 52
148 152 117 120 152 143 65 62 51 51
54 ISDIVIDUAL READING 69 70 70 69 70 69 68 71 48 47 49 52 49 51 51 48 49 49 48 51 51 51 49 50 49 46 46 48 46 48 51 46 29 24 26 28 25 25 28 28 ISDIVIDUAL READING 25 26 28 25 25 28 27 26 30 32 28 29 30 32 28 28 14 16 16 14 14 16 16 16 14 14 16 15 15 15 14 15 18 15 14 14 16 15 16 15
Av. 152.4 155.4 115.0 118.8 146.0 145.4 64.6 64.0 53.4 53.0 Av. 68.8 69.4 49.4 49.8 49.8 50.0 48.2 41.8 26.6 26.4 AV. 26.2 26.0 30.2 29.4 15.4 15.2 15.0 14.6 15.4 15.4
T h e results indicate t h a t variations between t h e individual readings may be considerable, b u t t h a t t h e averages of five readings are well within t h e liinits necessary for this character of work. When a column of ~ j mm. o of turpentine is equivalent t o a No. I yellow glass a difference of I O mm. in t h e length of the column is equivalent t o less t h a n 0.07 yellow. This variation in the color scale seldom occurs between t h e averages of five readings. I n no case has the color between the averages of five readings exceeded 0 .OS yellow, which is well within t h e limits required in the grading of turpentine. The instrument is easily adjusted, a n d t h e readings are made rapidly and with little strain and annoyance, Though it has been used here only in reading the color of turpentine it is obviously equally adaptable t o colorimetric work when t h e standard glasses can be employed and when t h e solution does not a t tack the metallic cell, in which case t h e cell should be made of a resistant material. LEATHER AND BUREAUOF
PAPERLABORATORY
CHEMISTRY, W A S H I N G T O N
j21
A KJELDAHL FUME REMOVER B y F. G. MGRKLE
Received March 30, 1916
Anyone who has ever had occasion t o make Kjeldahl nitrogen determinations knows t h e irritating nature of t h e fumes given off in t h e early stages of digestion. Some of t h e common appliances for the removal of these fumes are t h e following: I-Closed hood with ventilator. -.-The Johnson digestion pipe, which may lead directly into a flue or into a tile receiving a spray of water as proposed b y Wagner.' 3-The invaginated pipette (Folin). 2 4-The bulb condenser (Sy). The strong suction in the Folin and also the Sy apparatus has a number of disadvantages: ( I ) It reduces the pressure on t h e liquid, thus increasing t h e time required for digestion; ( 2 ) it produces a partial vacuum which increases t h e tendency t o foam, especially with organic materials; (3) it causes spattering and blackening in t h e neck of the flask which is greater as t h e pressure on the surface becomes less. Bits of digesting material and drops of acid may be carried far u p into the neck of t h e flask necessitating attention during the operation. A ?SEW A P P A R A T U S
The apparatus illustrated b y Fig. I has been in use for a year in the course in General Chemistry of t h e
FIG.I
institution with which t h e writer is connected,and has given good results. It consists of a lead pipe ( A ) , ' 1 2 in. inside diameter, t o which are soldered as many 3-in. lead tubes, '/a in. in diameter, as there are Kjeldah1 flasks. Each small t u b e is fitted with a rubber stopper (C) t o accommodate t h e mouth of t h e flask. Caps ( D ) made by boring holes one-half way through rubber stoppers are handy t o plug u p unused tubes. One end of t h e main pipe ( A ) is plugged with a stopper, the other fitted with a bent glass t u b e which serves as a n outlet for t h e fumes. The whole is supported b y clamps as seen in Fig. 11. The pipe is easily bent so i t should be supported a t intervals of not more t h a n I ~ / Z t o z ft. I t is sometimes found advantageous t o lower the end of t h e pipe nearest the sink so t h a t there will be a fall of z or 3 in. in j ft. of pipe. This aids, somewhat, t h e outward movement of the fumes of condensed acid. T h e expanding fumes force their way slowly out of t h e tube ( F ) and may be disposed of b y letting it project a foot down the sink pipe which is washed with a small stream of water. 1 2
3
Chen.-Ztg., 36 (1912). 1438. J . B i d . Chem., 2 (1912). 503 THISJOURNAL, 4 (1912). 680
T H E J O U R X . 4 L O F I S D U S T R I A L AIVD E N G I N E E R I X G C H E M I S T R Y
522
V d . 8, No. 6
MODIFICATIOKS: 1-In place of a rubber stopper (G) and glass tube as shown in Fig. I, i t would be more desirable t o continue the lead pipe down into the sink by means of a right angle bend 2-
