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
Apr., 1914
in a t e s t tube and after displacement of t h e air in t h e tube, collecting the evolved gas over water. Successive dilutions of this were made and I O to I O O cc. portions of t h e final mixture, corresponding to t h e volumes of carbon monoxide shown in Column 2 of the accompanying table, were introduced into partially evacuated 2 j o o cc. bottles a n d these samples, which contained from 36 t o 3 6 0 parts of carbon monoxide per million, were drawn through the absorption apparatus as described above. DETERMINATIONS U P O N M I X T U R EOF S KNOWN AMOUNTS OF PURE CARBON AIR MONOXIDEA N D LABORATORY COz BULBS Q IODINEB U L B S P I O cc. approx. CO? B U L B S B 5-10 cc. aq. 1% 0.005 N Ba(OH)? I O cc. approx. 0.1% starch used for each det. KI 0 05 N Ba(OH)r used for each det. -----c I3 used for each det. , _ _ * , (COOH)z (at 0' and 0.001 A' Calc. CO for Calc. CO (COOH), for Calc. 760 mm.) excess of parts thio. for (at O o and excess (at 0' and per 2.500 Ba(OH)Z CO? per evolved I 760 m m . ) B a ( 0 H ) s 760 mm.) cc. of air. cc. cc. cc. cc. cc. 10,000 cc.
+
-
0.90 0.456 0.456(ai 0 45 0,229 0.229(a) 0.228 0 . 22s n , 225 n , 092
..
..
2.6 4.35
13.0 6.0
..
..
3.3
10.2 5.4 7.2
4.5
4.0.5
4 2
0.09
0.09 n.nn
.. 4 2
( a ) The mixture of CO
6.6
.. .. 6.6
14.8 7.65 7.3 7.5 4.0 3.8 4.1 4.1 3.95 1.85 1.75 1.75 0.2
0.79 0,405 0.386 0.40 0.207 0.196 0.212 0.212 0.20 0.09 0.084 0.084
...
for t h e concentrations of carbon monoxide under consideration, no increased confidence in the results is t o be obtained by using t h e carbon dioxide titration as a check upon the iodine titration. HYGIENICLABORATORY, WASHINGTON, D. C
CONVERSION CURVE FOR LOVIBOND'S TINTOMETER AND STAMMER'S COLORIMETER B y CARLA. NOWAK Received January 20. 1914
I n compliance with a request recently received asking me t o construct a table correlating the readings taken on the Lovibond tintometer, inch cell, series j 2 , and those obtainable with the Stammer colorimeter, I have carried out a number of comparative color determinations with these two instruments using a n 8 % malt wort, and plotted t h e results in a form of a conversion curve. I n order to verify the readings and to determine the extent of experimental error due to personal factors, such as variation in color vision, all readings
..
...
2.15 2.55
0.345 0.30
2.8 3.8 3.35
0.28 0.18 0,225
60
...
ss
..
..
...
..
...
4.3
0.13
..
.. 4.9
323
...
...
50
...
+ air stood over water two days before analysis.
Factor for 0.001 N thiosulfate = readings X 0.97 = 0.001 A' exactly. 1 cc. 0.001 X thiosulfate = 0.056 cc. CO (at 0' and 760 mm.). 10 cc. approx. 0.05 N B a ( 0 H ) z = 5.85 cc. (COOH),; 1 cc. (COOH)g = 1 cc. COI (at 0 ' and 760 mm.). 10 cc. approx. 0.005 N B a ( 0 H ) s = 5.6 cc. (COOH)?; I cc. (COOH)? = 0.1 cc. CO? (at 0" and 760 m m . ) .
Blank determinations made by drawing 2 5 0 0 cc. portions of laboratory air through t h e iodine pentoxide tube heated to x j o 0 , gave blue colorations in bulbs P which required 0.2 cc. and sometimes as high as 0.4 c c . of 0.001LV thiosulfate for their discharge. These amounts, no 'doubt, correspond t o the carbon monoxide normally present in t h e laboratory air and do not indicate a faint spontaneous decomposition of the iodine pentoxide. The correction of 0.2 cc. has therefore been applied to the thiosulfate titrations given in the table, since in these cases t h e estimation of the added carbon monoxide only was desired. I t will be observed t h a t in t h e present experiments slightly low results for carbon monoxide were obtained in all cases. The amounts recovered varied from 88 t o 98 per cent, t h e lower percentages being obtained with t h e higher amounts of carbon monoxide. 'Although on the percentage basis this appears t o be a considerable loss, as a matter of fact when the very minute amounts of gas are taken into consideration t h e differences are quite small. In regard to the carbon monoxide determinations based upon t h e titrations of the contents of bulbs Q it is seen t h a t unaccountable irregularities are obtained. Tn most cases t h e amounts of carbon monoxide recovered were considerably lower t h a n found by the iodine titration. I t may, therefore, be concluded t h a t
4s
40
3s
30
26
29
15
0
5
3
>
,5
20
25
30
35
4-0
4s
50
55
were taken b y two persons, with the unexpected result, t h a t in no case did the readings vary by more than 2 degrees Stammer or more t h a n 0.2 to 0.3 degree Lovibond. All readings were taken a t the same temperature, a h . , I j Centigrade. After plotting t h e tabulated results i t was found t h a t an almost ideal curve was obtained, showing t h a t with a careful manipulation very slight differences in color can be detected with either of these instruments. For the benefit of any who may not have access to both instruments and wish to convert the readings of
3 24
T H E J O U R N A L OF I N D U S T R T 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
o,ne into t h e other, the conversion curve, which is selfexplanatory, is herewith given, inasmuch as, t o t h e author's knowledge, a curve of this kind, or a table of conversions, is a t present nowhere available. CHEMICAL LABORATORY THEwhi. R A H R SONS' C O . MANITOWOC, WISCONSIN
APPARATUS FOR THE DETERMINATION OF FAT BY THE ROESE-GOTTLIEB METHOD' B y WILLIAMBRINSMAID
Wishing t o use t h e Roese-Gottlieb method for t h e determination of f a t in evaporated milk as published in Circular No. 66 of t h e Bureau of Chemistrv. i t was found t h a t t h e - 'Rohrig tubes for this purpose could not be purchased. None of t h e dealers in chemical glassware of whom inquiries were made, knew anything of them. The writer had seen t h e tubes designed by Mr. Patrick, b u t wished a tube differing from t h e m in some respects. As there is nothing complicated about these tubes, specifications were drawn up and the tubes ordered from t h e glass-blower. The specifications were determined by sealing t h e end of a glass tube of five-eighths of an inch inside diameter and using the amounts of material required in exactly the s a m e way as in an actual determination. After t h e mixture had settled for twenty minutes, marks were made on the tube in two places. T h e tube was first marked a t t h e lowest point on t h e column of ether a t which the ether could
be safely drawn o f f . The second mark was made above t h e t o p of t h e ether column a t a height t h a t would allow space for proper mixing. T h e t u b e was then emptied and these two points were measured in cubic centimeters. They were found t o be 19.5 1 Presented a t the 16th Annual Association of Food, Dairy and Drug 0 5 c i a l s . Seattle, July 9-12, 1912.
Vol. 6 , No. 4
and 85 cubic centimeters, respectively. The specifications were as follows: I . Inside diameter of tubing t o be five-eighths of a n inch. 2. Drainage tube t o be so placed t h a t t h e bottom of t h e orifice is a t t h e 19.5 cc. point. 3 . Capacity of t h e tube t o be 8 5 cc. 4. Mouth of tube t o be constricted t o fit the taper of a cork stopper. A rough drawing was sent with the specifications. Fig. I shows an empty tube and Fig. 2 shows a tube with a fat determination in it. The height of t h e emulsion in t h e tube can easily be seen. With some milks t h e emulsion may stand a very little higher, but as yet there has been no difficulty with the tubes made as specified. The tubes being awkward t o handle and t h e drainage cock rather fragile, t h e problem of a safe and convenient mode of handling presented itself. At first t h e tubes were set in perforated blocks b u t when handled in this way t h e mixing has t o be done singly and this is a rather slow method. Finally a tilting rack was designed of the form shown in Figs 3, 4 and 5 , and this has been found well adapted t o t h e purpose. Boiled cork stoppers are used in the tubes and if well fitted will hold the small pressure developed without trouble. The mixing of t h e milk with t h e ammonia and with t h e alcohol is done quickly while holding t h e tube in the hand and without using t h e stoppers. The tubes are then placed in t h e rack in an upright position and t h e ethyl ether added and the cork stoppers placed firmly in t h e tubes. The tilting frame with tubes is then turned back as shown in Fig. 3 and again turned t o a n upright position, and this continued a s long as necessary. The petroleum ether is then added and t h e process repeated. The rack is then placed in the position shown in Fig. 4,t h e wing-nut tightened t o keep i t a t this angle and t h e contents of t h e tubes allowed t o settle. This position prevents
t h e emulsion from running into t h e outlet tube, which i t is liable t o do if t h e mixture is allowed t o settle with t h e tube in an upright position. In this way six determinations can be extracted in t h e time t h a t would be required b y one if held in the hand' as the tubes are not in a warm hand, there is less pressure developed. After
