OCt.,
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
1915
ESTIMATION O F SELENIUM I N SULFUR By W. SMITH Received M a y 21, 1915
T h e separation used depends upon t h e facts t h a t t h e bromides of sulfur a n d selenium when shaken with excess .of cold water decompose according t o t h e following equations, zS2Br2 3 H 2 0 = H2S03 3s 4HBr, SeBrr 3 H 2 0 = H2Se03 4HBr, a n d t h a t t h e decomposition of t h e selenium compound proceeds very rapidly compared with t h a t of t h e sulfur compound. When t h e acids of selenium (small amounts of selenic acid being present, due t o oxidation of selenous acid b y bromide water) are heated with excess of hydriodic acid t h e y are reduced t o selenium' as follows: H2Se04 6HI = 4 H 2 0 312 Se 4HI = 3H20 H2SeO3 212 Se I n order t o test t h e completeness of t h e above reaction a standard solution of selenic acid was prepared from selenium purified from four precipitations, a n d t h e selenium contained was estimated as described below, with t h e following results:
+ +
+ +
+ +
+ +
%3LENIU&f
Added, g r a m F o u n d , gram
. .
1 0.0160 0.0158
2 0.0586 0,0590
+
+ +
3 0.0586 0.0590
1.4
W. Pearce, Research Papers
1901), 338.
of
Kent
T h e free iodine is removed b y t h e addition of a few cc. of t h e solution of potassium metabisulfite or sulfite. Boil for 2 0 minutes, filter through a tared Gooch crucible, wash t h e selenium with hot water, a n d dry a t 100' C. until a constant weight is obtained. T h e method has been found t o work successfully on standard sulfur samples which were prepared as follows: Yo. I-By mixing red selenium with sulfur. No. z-By mixing black selenium with sulfur. N o . 3-By melting black selenium with sulfur KO. 4-By melting black selenium with arsenic a n d sulfur in t h e molecular proportions of 4S2SSe?. T h e following results were obtained b y t h e above method with from I O t o 30 grams of t h e standard sulfur samples. so. 1 REDSELENIUM MIXEDWITH SULFUR Amount Amount added found Gram Gram Error 0.0454 0.0469 +0.0011 0,0405 0.0410 j-0.0005 0.0454 0.0460 0.0006
.. ..
Chemical Laboralory, 1
-
..
.. ..
..
4 0.0586 0.0590
T h e details of t h e method, based upon t h e above reactions, are as follows: Weigh a q u a n t i t y of finely ground sulfur (preferably about 5 0 grams) into a n Erlenmeyer flask, t h e n a d d a few cc. more bromine t h a n grams of sulfur used; allow t o s t a n d for fifteen minutes (it is advisable t o conduct this work in a fume cupboard in which a little ammonia has been sprinkled). Transfer t o a I O O cc. separating funnel a n d shake vigorously with 40 cc. of bromine water for I minute; separate t h e sulfur bromide from t h e aqueous solution, a n d pour t h e latter through a wetted filter paper. Add about z cc. of bromine a n d 4 0 cc. bromine water t o t h e sulfur bromide, a n d repeat t h e extraction four times, t h e last extract being kept separate. If insufficient bromine be added sulfur separates during extraction; this can be avoided b y t h e addition of more bromine t o t h e sulfur bromide. If t h e q u a n t i t y of sulfur in t h e aqueous solution be small it can be removed b y boiling t h e bromine water. T h e last extract is treated in t h e same way as t h e combined first extractions (proportionate a m o u n t s of potassium iodide, a n d hydrochloric acid being used). If t h e presence of selenium be proved in this last portion, extraction is repeated a s often as necessary. The solutions, which must contain a n excess of bromine, are boiled till clear; a n y remaining free bromine is removed b y careful additions of powdered potassium metabisulfite. or sulfite, until t h e solution just becomes colorless. T h e selenium in t h e red form may commence t o precipitate at this stage. Dilute t o a b o u t 2jo cc., a d d 1 5 cc. of hydrochloric acid a n d a b o u t 5 grams of potassium iodide a n d boil; this completes t h e precipitation of t h e selenium, a n d gradually converts t h e red into t h e black allotrope.
849
h70. 2
BLACK SELENIUM
.. ..
..
-4mount added Gram 0.0390 0.0488 0.0341 0.0488 0,0488 0.0219
MELTEDWITH SULFUR
Amount added Gram 0.0227 0.0488 0.0488 0.0171 0.0488 0.0244
Amount found Gram 0.0220 0.0478 0.0492 0.0171 0.0490 0.0250
Error -0, OOOi -0.0010 i-0,0004 0,0000
t-0.0002 +0.0006
Amount found Gram 0.0390 0.0493 0.0338 0.0497 0,0488 0.0212
SULFUR
Error 0.0000 + O . 0005 -0.0003 +0.0009 0,0000 -0.000;
No. 4
170.3
BLACK SELENIUM
M I X E D WITH
BLACK S E L E N I U M M E L T E D W I T H ARSENIC A N D SULFUR IN h l O L E C U L A R P R O P O R T I O N S OF AS2SSez A N D THEX b I I X E D WITH EXCESS OF SULFCR
Amount added Gram 0.0244 0.0488 0.0488 0.0283 0.0464
..
Amount found Gram 0.0?52 0.0496 0.0495 0.0280 0.0470
..
Error +0.0008 +0.0008
+0.0007 -0.0003 C0.0006
..
A number of samples of commercial sulfur were analyzed a n d t h e following are some of t h e results obtained from Japanese samples: Per cent a r s e n i c . . . . . . . . . . . 0 . 8 0 Per cent selenium.. . . . . . . . 0 . 1 5 2
0.iO 0.085
0.50 0.055
0.30 0.045
I t will be noted t h a t there would appear t o be a certain parallelism between t h e amounts of arsenic a n d selenium present in t h e above .samples. Tellurium, if present, will be estimated as selenium b y this method, b u t examination of several samples of crude selenium obtained from sulfuric acid chambers proved t h a t it was present in very small quantity, if at all, t h e maximum being 0.1per cent of t h e selenium present. T h e method used for t h e determination of tellurium was t h a t of Browning a n d Flint' which is given below. If a sample of sulfur containing both selenium a n d tellurium be encountered, t h e y could be estimated b y t h e method described for t h e estimation of selenium, a n d tellurium could be determined as follows: Dissolve t h e mixed selenium a n d tellurium which is contained in t h e Gooch crucible in a small quantity of hot, strong nitric acid; gently evaporate t h e solution just t o dryness; dissolve t h e mixed oxides of tellurium a n d selenium in a small quantity of I:Z hydrochloric acid, a n d warm for a few minutes. Dilute this solution with 2 0 0 cc. of boiling water a n d a d d ammonium 1
Browning and Flint, A m . J . Sci., 28 (4th Series) (1909), 112.
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
8 SO
hydroxide in very slight excess; t h e n make very slightly acid with a drop or two of acetic acid, allow t o s t a n d for 30 minutes a n d cool. Now decant t h e liquid through a tared Gooch crucible, a n d wash t h e tellurium dioxide with cold water a n d d r y a t about 1 1 0 ’ C. until constant weight is obtained. LABORATORY CUMING SMITH 82 CO. PTY., LTD. YARRAVILLE, MELBOURFE,AUSTRALIA
EFFECT OF FREE FATTY ACIDS UPON THE FLASH AND FIRE POINTS OF ANIMAL FATS AND OILS B y ARTHURLOWENSTEIN AFD J. J. VOLLERTSEN Received July 2, 1915
T h e authors having frequently noticed t h a t t h e presence of a n appreciable amount of free f a t t y acids in f a t s a n d oils depressed t h e flash a n d fire points of t h e fats or oils; a n investigation was made t o determine t h e relation between samples containing varying amounts of free f a t t y acids, t h e neutral glycerides, from which t h e free f a t t y acids were derived, a n d t h e t o t a l f a t t y acids of t h e f a t s a n d oils themselves. It will be noted from Table I t h a t in every case t h e presence of free f a t t y acids depresses t h e flash a n d fire point. The flash a n d fire determinations of t h e total f a t t y acids readily explains why this is true. A s t u d y of t h e d a t a reveals interesting relations between flash a n d fire tests of t h e total f a t t y acids of different f a t s a n d oils as well as t h e tests of their neutral glycerTABLE I-EFFECT
OF FREE FATTY ACIDSUPON THE FLASH A N D FIRE POTXTS OF ANIMAL FATSAND OILS Temperatures given in degrees Fahrenheit FREE ORIGINAL KEUTRAL TOTAL FATTY SAMPLE GLYCERIDES FATTYACIDS ORIGINAL ACIDS Flash Fire Flash Fire Flash Fire 9?? test test test test test test SAMPLE .. Acidless tallow o i l . . . . , , , 0 . 2 0 620 670 624 668 368 438 0.50 616 674 624 682 370 432 Extralard oil . . . . , . . . . . . 2 . 3 0 540 665 598 677 368 428 Off Prime” lard o i l . . . . . 3 . 6 5 504 622 604 676 376 436 No. 2 lard oil , . . . . . . . . . . 3 3 . 1 5 418 472 620 672 370 436 “AA” white grease . . 2 . 0 0 518 648 554 656 372 420 “A” white grease . . 4.05 488 628 548 646 350 412 Prime tallow . . . . . . . .. . . . 2 . 5 506 630 550 652 342 406 Packers’ No. 1 tallow .... 8 . 9 0 490 526 536 666 374 424 Packers’ No. 2 tallow . . . . 3 7 . 5 364 394 510 595 342 416 ~~
. ... .. .. ..
ides. A s t u d y of t h e flash a n d fire tests of t h e oils themselves reveals t h e fact t h a t with a n increase in t h e free f a t t y acid content there is a corresponding decrease in t h e flash a n d fire tests. A similar investigation is under way relative t o t h e influence of the presence of free f a t t y acids on t h e flash a n d fire tests of vegetable a n d fish oils. T h e method of preparing t h e neutral glycerides a n d t h e t o t a l f a t t y acids was as follows: t h e neutral glycerides were prepared by shaking out t h e sample with alcoholic solution of caustic potash. The required amount which was necessary for exact neutralization was figured out from t h e percentage of free f a t t y acids present a n d a slight excess over this amount added. After shaking, t h e solution was allowed t o settle out in t h e cold a n d t h e f a t carefully drawn off, washed once with 50 per cent alcohol a n d four or five times with distilled water. T h e f a t was t h e n filtered a n d dried before t h e flash a n d fire determinations were made. T h e t o t a l f a t t y acids were prepared by saponifying t h e f a t entirely with alcoholic soda, driving off t h e
Vol. 7 , No.
IO
excess of alcohol, dissolving in hot water, a n d precipitating by means of I:I sulfuric acid. The f a t was thoroughly washed with water, filtered and dried. T h e Cleveland open fire tester was used for determining t h e flash a n d fire tests. T h e authors desire t o express their thanks t o hIr. P. Malekow who assisted in t h e analytical work. COMPANY CHEMICAL LABORATORY CHICAGO
IVfORRIS A N D
THE LYE HULLING OF CORN FOR HOMINY B y J W. MARDEP;A N D J. *4.MOXTGOMERY Received May 7 , 1915
T h e method of hulling “home-made” hominy is a simple process. Enough lye is added t o water in a large iron kettle t o make t h e solution feel slippery t o t h e fingers a n d field corn is boiled therein until t h e tips of t h e corn slip off easily. T h e tips a n d t h e hulls are often rubbed off b y h a n d , after which t h e corn is carefully washed. The washing is usually done by simply hanging t h e basket containing t h e corn in a stream of flowing water a n d leaving i t there, sometimes for two days. Such a method leaves much t o t h e discretion of t h e operator. I n t h e factory this method is employed with modifications. The corn used is carefully selected of t h e best white variety. T h e hulling is done in large wooden t a n k s which have drains a t t h e bottom a n d inlets for cold a n d hot water a t the t o p . These t a n k s are fitted with large iron stirrers for t h e vigorous agitation of t h e lye liquor a n d have a capacity of about t e n t o twenty bushels of corn. T h e corn t o be hulled is dumped into t h e v a t , t h e v a t filled with hot water, which is kept hot with live steam, or cold water heated with live steam, a n d t h e stirrer started. The lye is poured in when t h e liquid is well heated a n d t h e hot mixture stirred until t h e black tips of t h e corn are loosened; then t h e lye liquor is drained off. The corn is washed in t h e hulling t a n k s first with hot a n d t h e n with cold water until t h e lye is removed a n d a t t h e same time t h e friction of t h e stirrers removes t h e loose tips, which are floated off with t h e wash water. This process of hulling a n d washing usually takes about three hours or more. This is t h e older process of hulling. I n many factories now t h e corn is kept in t h e lye liquor b u t a short t i m e a n d t h e n p u t through a hulling machine which removes t h e hulls a n d tips by friction. ( I n t h e experiments described in this paper t h e corn was k e p t in t h e lye liquor until t h e tips a n d hulls were all loosened a s is still t h e practice in many factories.) Without further t r e a t m e n t t h e corn is scalded in especially constructed wire baskets a n d mechanically p u t into cans. These are moved on a belt through hot water, usually containing a little salt, a n d this liquid fills them. T h e corn is cooked for several hours under pressure after i t is sealed in t h e cans. It was found, upon examining six well known brands of lye hominy, t h a t two showed a large number of black grains, about one grain in t w e n t y being black, while t h e remainder of corn in these cans was of per-
