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necessarily below t h e minimum for all samples of known purity. This is particularly so when dealing with herd milk. I n t h e absence of a refractometer, . t h e specific gravity or t h e per cent of solids of t h e serum is just a s valuable as t h e refractive index i n detecting added water. T h e writer wishes t o acknowledge his t h a n k s t o his assistants, Messrs. Charles H . Hickey, Louis I . Xurenberg, a n d Clarence E. Marsh, t o whom he is greatly indebted for their valuable cooperation in making t h e analyses of t h e samples.
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(ether was used) a n d t h e latter evaporated. A small a m o u n t of oil remains. A piece of copper wire is heated in a colorless gas flame until i t is black a n d n o longer colors t h e flame green. T h e hot e n d of t h e wire is dipped into t h e oil a n d again brought into t h e flame. If chlorine or bromine has been used as a bleaching agent a green or blue coloration is produced.” RIoisture determinations were made by drying t h e samples for five hours in a steam oven a t t h e temperat u r e of boiling water. The determinations of acidity were made in accordance with Method j in Bull. 152, of t h e Bureau of LABORATORY OB FOOD A N D DRUGINSPECTION Chemistry, U. S. Department of Agriculture. rvhich M A S S A C H U S E T T S S T A T E BOARDOF HEALTH is as follows: T o 20 grams of flour in a 500 cc. E r BOSTON lenmeyer flask a d d zoo cc. freshly boiled water. Digest at 40’ C. for t w o hours, shaking a t Io-minute intervals. SOME CHARACTERISTICS OF CHLO RINE-BLEACHED Decant t h e clear liquid through a folded filter a n d tiFLOUR t r a t e jo cc. N / z o K a O H . B y c. A A. UTT Table I indicates t h e results obtained on inspecReceived July 3, 19 14 tion samples. I t will be noted t h a t t h e moisture does Since t h e Government ruled against flour treated with t h e oxides of nitrogen (F. I . D. 100;S. T. 7 2 2 , not v a r y any more between t h e bleached a n d unU . S. D e p t . of Agr.), chlorine-bleached flour has made bleached flour t h a n might be expected in duplicate its appearance. United States P a t e n t I , O ~1 ~ 9 7 7 , determinations. An increase in acidity in t h e bleached TABLE I-SOME C H A R A C T E R I S T I C S O F C H L O R I X E - B L E A C H E D FLOLR September 2 9 , 1913, deals with a process in which “flour is treated with anhydrous chlorine (diluted with a n inactive gas) in order t o mature a n d whiten it.” This process a n d a few others in which chlorine is t h e active agent are used. By this means, i t is claimed, 13.36 0.126 484. - 1870 43 1 12.99 94 95 46-47 Unbleached patent t h e flour is whitened a n d aged. Bleached p a t e n t L3.68 0.144 764 + 1860 4 2 8 13.07 93 94 14.22 0.198 532 - 1780 47 5 T h a t chlorine w.il1 bleach flour has been known for 48-45 Unbleached, clear 16.10 , 83 14.18 0.288 916 f 1800 48 6 16.07 . , 85 Bleached, clear m a n y years, b u t its activity a n d difficulty of control 5 2-5 4 P a t e n t unbleached 10.70 0.162 442 - 1940 38 87 12.67’ 93 92 11.12 0.18 881 + 1950 39 16 12.87 93 89 a t e n t bleached have caused its use t o be viewed with suspicion. 65-66 PUnbleached 12.66 0.126 556 - 2020 3 9 3 4 12.40 94 92 patent 12.88 0.126 648 f 1980 39 98 12.92 93 89 Bleached patent I n connection with t h e pure food work of Kansas i t 95-96 Unbleached 12.20 0.144 494 - 1920 41 83 14.05 94 94 12.24 716 f 1970 41 78 13 67 93 94 Bleached was found necessary t o collect some information on 9 1-92 P a t e n t unbleached 13.10 0.189 0.126 540 13.12 0.135 844 + P a t e n t bleached chlorine-treated flour. T h e results of this investiga12.44 0.216 504 51-55 Unbleached, clear 12.32 0.252 928 + Bleached. clear tion are presented in this paper. 11.46 0.189 544 97-98 Unbleached Samples were obtained directly from t h e mills b y 11.40 0.198 868 f Bleached 10.99 0.198 736 f 70299 Bleached t h e Kansas food inspectors, of t h e same flour before 70300 Bleached 11.22 0.207 900 + 12.88 0.306 576 a n d after bleaching. These were placed i n screw- 65-63 Unbleached 12.69 0.324 667 f Bleached 12.56 0.18 501 t o p glass jars, sealed a n d shipped t o t h e laboratory. 70-72 Unbleached 12.68 0.234 972 + Bleached 12.42 0.216 496 T h e following determinations were made: ( I ) Chlorine 73-7 1 Unbleached 12.42 0.270 855 + Bleached qualitatively a n d quantitatively; ( 2 ) moisture; (3) acidity. A number of gluten a n d baking tests were flour as compared with t h e corresponding unbleached sample is noted in nearly every instance. The chlorine also made. Chlorine was determined b y Jacobs’ method as content varies from 442 parts per million t o 576 p a r t s used in t h e Plant Chemistry Laboratory of t h e U. S. per million in t h e unbleached flour; when bleached Department of Agriculture. It is as follows: “TO t h e variation is 648 t o 9 7 2 p a r t s per million. All bleached samples reacted positively with the copper 2 5 grams of flour in a platinum dish, a d d z j cc. of a solution containing 2 5 grams of K O H a n d 2 5 grams wire reaction for chlorine. T h e differences i n loaf volume are not much greater K N 0 3 per liter. Evaporate t o dryness on a steam b a t h , a n d ignite in a muffle a t a dull red heat until t h a n one would expect t o find in individual loaves thoroughly charred. Extract t h e charred mass with from t h e same flour. Loaf volume favors t h e unbleached 2 j cc. j per cent “ 0 3 ; filter. R e t u r n residue t o t h e flour in some cases, in others t h e bleached flour. All platinum dish, char further a n d extract again with loaves were graded against a standard loaf made from hard wheat flour under t h e same conditions, as is t h e z j cc. 5 per cent H N 0 3 ; filter, wash with h o t water, a n d ignite t o a n ash. Dissolve t h e ash in j per cent custom. I t will be noted t h a t in nearly every case HNO,, filter a n d wash. Combine t h e filtrates a n d de- t h e bread made from t h e unbleached flour grades better. T h e bleached flour gives a loaf having a n objectionable termine t h e chlorine with silver nitrate.” Qualitative determinations of chlorine were made color a n d texture. T h e gluten tests r u n practically uniform for t h e b y t h e copper wire method as given b y Alway (Bull. bleached a n d unbleached flour. there being no more 102, Nebraska Experiment Station, page 5 3 ) as follows: difference t h a n on duplicates. However, physically “One ounce (30 grams) of flour is extracted with benzene
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t h e gluten of t h e chlorine-treated flour is somewhat softer i n some cases, showing t h a t t h e chlorine m a y have affected t h e gluten t o some extent. Several samples of unbleached flour gave t h e following a m o u n t s of chlorine, expressed in p a r t s per million: (1) 445; ( 2 ) 503.8;(3)492; (4) 448; (5) 348; (6)3 7 3 ; ( 7 ) 4 5 2 ; (8) 484; (9) 496; ( I O ) j44. A number of samples of chlorine-treated flour on t h e Kansas market yielded t h e following amounts of chlorine expressed in parts per million: ( I ) 7 4 2 ; (2) 260; (3) j91;(4) 608; (5) 7 3 2 ; (6) 7 1 2 ; ( 7 ) 1056; (9)904. All of these gave a positive test with t h e copper wire reaction. A number of samples of bleached a n d unbleached flour were shipped t o t h e laboratory in cloth sacks, packed together. T h e unbleached flour yielded t h e following amounts of chlorine, p a r t s per million: ( 1 ) 5 2 8 ; ( 2 ) 5 5 2 ; (3) 612, ( 4 ) 598; ( 5 ) 592. I n each case a slight color developed i n t h e copper wire reaction, showing t h a t some chlorine was probably t a k e n u p by t h e unbleached flour. A sample of soft wheat gave 4 5 2 p a r t s chlorine per million; a sample of hard wheat gave 496 parts, a n d t w o samples of bran gave 464 a n d 431 p a r t s chlorine per million. S U M MA R Y
T h e chlorine content of untreated flour m a y r u n as high as j76 parts per million. Chlorine-treated flour will contain over 600 p a r t s per million of chlorine. T h e chlorine can be detected with certainty b y means of t h e copper wire reaction. Samples of u n bleached flour in contact with chlorine-treated flour m a y give t h e reaction. Chlorine-treatment increases t h e acidity of t h e flour a n d does not improve its breadmaking qualities. I n conclusion credit should be given t o hIiss Leila D u n t o n of t h e Department of Milling I n d u s t r y of t h e Kansas S t a t e Agricultural College for making t h e baking a n d gluten tests, a n d t o D r . J . T. Willard, of t h e Department of Chemistry, for suggestions in carrying o u t t h e work. KANSASSTATEAGRICULTURAL COLLEGE MANHATTAN
DETERMINATION O F PRUSSIAN BLUE I N TEA' B y G W. KXIGHT Received August 31, 1914
This method of determining t h e artificial coloring m a t t e r , Prussian blue, on t e a is t h e conclusion of a series of experiments t o ascertain a n analytical method t h a t would be rapid, accurate a n d quantitative. By means of i t , I p a r t in zoo,ooo, a n d sometimes even I p a r t in 300,000, can be detected. A m a n inexperienced in t h e manipulation can r u n four determinations in a d a y easily, a n d doubtless with experience could r u n m a n y more. T w o operators viorking independently on t h e same sample obtained 0.0019 a n d 0.0016per cent of Prussian blue. METHOD--100g. of t e a are ground t o a fine flowder in a coffee grinder, placed i n a round-bottomed distilling flask of sufficient capacity a n d moistened with enough 8 5 per cent phosphoric acid t o thoroughly 1 Contributed with t h e permiqsion of t h e Secretary of t h e Treasury . a n d t h e U. S. Appraiser, Port of h-ew York.
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moisten all of t h e tea. (Usually from 30 cc. t o 60 cc. are sufficient.) T h e flask is t h e n fitted with a delivery t u b e , which passes through a two-hole stopper into a mixture of 4 cc. of I O per cent K a O H solution a n d 30 t o 4 0 cc. of water contained in a I O O cc. Erlenmeyer flask. T h e Erlenmeyer flask is supported in a beaker of cold water. An outlet t u b e bent a t right angles passes through t h e other hole of t h e two-hole stopper for t h e escape of unabsorbed gases. T h e a p p a r a t u s is placed in a well ventilated hood a n d a Bunsen burner flame is placed in front of t h e outlet t u b e t o burn t h e unabsorbed gases. T h e flask is t h e n heated, slowly a t first, with a small flame a n d finally more strongly until t h e phosphoric acid begins t o distil over. Usually I O or I j minutes are sufficient for t h e distillation. After t h e distillation is completed, t h e distillate is filtered a n d t h e filtrate placed in a casserole; if acid, i t is neutralized with I O per cent N a O H solution, t h e n 3 cc. of I O per cent S a O H solution in excess are added. A crystal of FeSOl about t h e size of a pea a n d a few drops of I O per cent FeC13 solution are added a n d t h e solution boiled for I minute. HCl (sp. gr. 1.2) is t h e n added, drop by drop, t o t h e hot solution till it is distinctly acid. T h e solution is filtered a n d t h e precipitate washed with 95 per cent alcohol, until t h e washings r u n colorless. Cold I O per cent S a O H solution is dropped on t h e filter, using as little as possible b u t washing t h e whole area of t h e filter, a n d t h e n t h e filter is washed with as small a n amount of water as possible. I t is best t o drop t h e wash water, drop b y drop, from a pipette. About 4 cc. of N a O H a n d 8 cc. of water are sufficient for this operation. T h e filtrate is acidified with acetic acid a n d a few drops of HC1 (sp. gr. I.z), a few drops of I O per cent FeC13 solution are added a n d t h e n HC1 (sp. gr. 1 . 2 ) is added until a n y brown color t h a t m a y have developed has disappeared. T h e solution is t h e n placed in a casserole a n d evaporated t o half i t s bulk on t h e water b a t h ; more water is added t o dissolve a n y salts t h a t m a y have crystallized o u t , a n d t h e Prussian blue is Altered on a Gooch crucible, washed with very dilute HC1, water, alcohol a n d ether, a n d dried a t I O O O C. t o constant weight. T h e weight in grams gives directly t h e per cent of Prussian blue in t h e sample. Several samples of uncolored China and Japan teas were r u n b y this method, a n d n o Prussian blue detected. T h e n varying amounts of Prussian blue, from I p a r t in j j , o o o t o I p a r t in ~ O O , O O O , were mixed with these uncolored teas. Prussian blue was obtained in all cases up t o I p a r t in 200,ooo a n d in some cases u p t o I p a r t in 300.000. The amount appeared proportiona t e t o t h a t p u t in, b u t t h e a m o u n t was too small t o weigh except in t h e case of I p a r t in i j , o o o ; a n d in this case where I . j mg. was p u t in I mg. was recovered. As t h e purity of t h e Prussian blue p u t in was questionable, this mas a fairly quantitative recovery. Three samples which gave I spot, 2 spots a n d 3
