Spectrographic Examination of Organic Precipitates Nickel Dirnet hylglyoxime b14RG;IRET GRIFFINC', THOS. DE VRIES,
4ND
31. G . RZELLON, Purdue University, Lajayette, Znd.
Separation of nickel from seven times its weight of antimony, arsenic, barium, cadmium, calcium, magnesium, potassium, sodium, strontium, and zinc was obtained by precipitation with dimethylglyoxime. The precipitates were spectrographically free from these elements. Aluminum, chromium, copper, and manganese were definitely coprecipitated. The error introduced into the weight of precipitate by the chromium and manganese is insignificant.
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carbon electrodes and arcing for 60 seconds a t 9 amperes with 220 volts direct current. The exposure time was controlled with a rotating sector. Persistent lines (5)of the diverse ions were checked n-ith 3 traveling micronietzr in two n-ave-length ranges 2200 to %600A. and 3900 to 5300 A . , with a linear dispersion of about 5 A . per mm. on the plate. -1Baird grating spectrograph was used. ,
RGAXIC precipitating agents have found extensive use in quantitative analysis. T h e selectivity of these reagents and the lo17 perce:itage of metal in the resulting high molecular weight precipitates are two notable advantages. However, the large surface area oi these voluminous precipitates raised the question of the possibility of errors due to the adsorption of diverse ions. Since no information was available concerning the adsorptive properties of these organometallic precipitates and because of the extensive use of dimethylglyoxime for the determination of nickel, this system n-as srudied. T h e ashed precipitates were analyzed spectrographically for the presence of diverse ions. The use of dimethylglyoxime for the precipitimetric deterniination of nickel was first studied by Brunck ( 1 ) . Diehl ( 2 ) has written an excellent review of the subsequent studies. The most extensire study of the separation of nickel from other metals was made by Weeldenburg ( 4 ) ,mho reached the following conclusions:
RESULTS
Aluminum, Copper, Magnesium. The precipitate obtained from a slightly ammoniacal solut,ion in the presence of 1 gram each of aluminum, copper, and magnesium ions as sulfates was 1% too heavy. The spectrograph revealed conclusively t h a t aluminum and copper were contained in the nickel oxide. T h e evidence for magnesium was inconclusive; hence such a small amount would not cause a n error in the weight of t>heprecipitate. Sickel, 0.1486 taken; 0.1501 found. Weeldenburg ( 4 ) reported satisfactory separation of nickel from copper in a slightly acidic acetic acid solution. The precipitation was incomplete. The addition of ammonia to the mother liquor gave additional precipitate. However, the spectrographic d a t a indicated there was less contamination from the ammoniacal solution. Several attempts Tvere made to precipitate nickel completely from slightly acidic acetic acid solutions containing large quantities of copper. I n no case were good results obtained. Cadmium, Chromium, Zinc. I n accordance with the work of Keeldenburg 1-41, before the addition of dimethylglyoxime, the chromium was completely precipitated by a n excess of 6 Ai ammonia, then redissolved with concentrated hydrochloric acid. I n the first attempt t o precipitate nickel from chromium solutions, the tartaric acid was added after the precipitation and dissolution of the chromium hydroxide. Inconsistent results were obtained. However, if the tartaric acid was added first, excellent gravimetric results were obtained when the nickel dimethylglyoxime wa9 obtained upon the addition of ammonia. Spectrographic analysis revealed t h a t cadmium and zinc were definitely absent, and only a trace of chromium \vas indicated. Nickel, 0.1486 taken; 0.1485 found. Arsenic, Potassium, Sodium. Nickel was precipitated from a slightl). ammoniacal solution in the presence Qf ammonium arsenite, potassium chloride, and sodium chloride. None of these ions was detected in the precipitate. Kickel, 0.1486 taken; 0.1185 found. Manganese. According t o Diehl (Z), small amounts of manganese do not interfere with the precipitation from an nmnioniacal solution, However, Weeldenburg ( 4 ) reported t h a t if large amounts mere present the oxygen of the air caused a bwic hydroxide t o be precipitated; but, in the presence of tartwit acid, it offered no difficulties if the precipitation was from a n acetic acid solution. .\n attempt to separate 0.15 gram of niclicl ion from 1 gram of manganc5e (11) ion failed hrrause of precipitation of manganese tartrate by the addition of the :ilcnlicd containod in the reagent solution. Precipitation from a
Separation from aluminum, antimony, arsenic, cadmium, chromium, magnesium, iron, and zinc mas satisfactory from a slightly ammoniacal snlution in t,he presence of a large excess of ammonium chloride and tartaric acid. Bettw sepwation is obtained from bismuth, copper. and manganese if the precipitation is carried out in a solution slightly Tic :!cid. acidic 17 Lead nilry be retained in solution by an excess of ammonium acetate. EXPERI>\IENTAL
Reagent grade chemicals were used to prepare the solutions. sulfate and nickel nitrate solutions contained 3 T h e nickel ((111 grams of nickel per liter. T h e exact concentration was established both by precipitation of the dimethylglyoxime complex and by electrodeposition of nickel metal. Redistilled ethanol was used for the preparation of a 1%solution of dimethylglyoxime. Sickel was precipitat,ed from solutions containing 1 gram of diverse ions. These were weighed as dry salts, dissolved in 400 ml. of water, and acidified with 5 nil. of hydrochloric acid. Fiftp milliliters of the standard nickel sulfate solution were added. Five grams of tartaric acid were added for each gram of diverse ion and the solution was heated to 60" C. .%mmonia was added until the solution n-as slightly alkaline to litmus, then 5 ml. of hydrochloric arid and 80 ml. of the dimethylglyoxime reagent were added. The n i c l d complex was precipitated by the d p p wise addi:ion of 6 -\-ammonia with constant stirring at 60 * 3" C. The reaction n-as considered complete when 4 ml. of animonia had keen added in excess of that necessary to make t h e solution allialine t o litmus. The precipitates Tvere digested for an
the addition of the diiiiethylglyozime. as dc-
irnarc. Qualitative spectrographic analyses of
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S E P T E M B E R 1947 slightly acidic -acetic acid solution, viithout t h e presence of tartaric acid, gave escellent results. However, t h e spectrograph revealcd t h a t manganese \?-as definitely present in the precipitate. Kickel, 0.1486 taken; 0.1486 found. Antimony. Eight gramr of tartaric acid were necessary t o keep tlie ant,imnny (as the chloride! in solution. T h e gravimetric d a t a rrveal(Jd that the separation \vas good. Spectrographically no an:imony was indicated in the precipitate. Kickel, 0.1486 taken: 0.1187 found. Barium, Calcium, Strontium. \\-eeldenburg (4) reported that nickel rould not lie precipitated from a n ammoniacal solution in t h e prl:senw ?if iiarium, calcium, or strontium, because of their reaction with cnrtion dioxitlc t o form insoluble carbonates. fully precipitatrti from a n acetic acid solution,
655 free from sulfate and tartrate ions. T h e precipitate was not contaminated with the alkaline earths. Sickel, 0.1623 taken; 0.1623 found. LITERATURE CITED
(1) Brunck. O . , Z . angew. Chem., 20, 834 (1907). (2) Diehl, H., “Applications of the Dioximes t o Analytical Chem-
istry,” Columbus, Ohio, G. Frederick Smith Chemical Co., 1940. (3) “LI.1.T. 11-ax-eLength Tables,” Yew York, John Wiley 8; Sons, 1939. (4) Weeldenburg, J. G., Chem. Weekhlad, 21, 358 (1924).
A s s T i u c T m from part of a thesis subniitted b y Margaret Griffing i n partia fulfillment for the P h D. degree.
Physical and Chemical Methods for Characterizing Peanut Butter J . F. VINCEST‘ fr\D L. Z. S Z . i B 0 , Southern Reseurch I n s t i t u t e , Birmingham, Ala.
Quantitatire procedures for the physical and chemical characterization of peanut butter, with special emphasis on factors which influence spreadability and oil separation, are described. Values obtained on experimental and commercial samples of peanut butter are included.
T
HE marked expansion of the peanut industry in recent years car1 br traced in part to a steadily increasing consumer acceptanrc. oi’ peanut butter as a staple item of diet. T h e national consumptioil I ~ O Kesceeds 2 pounds per capita annually. Meanwhile tliorc has been a gro\ving realization among progressive peanut butter manufacturers t h a t more suitable laboratory re neerled to assist in the maiiitenance of product quality )rmit>-. Although analyses of peanuts and peanut butters have been reported ( 4 , 8,. 9), no directions particularly well suited to peanut butter characterization have been presented. This paper sets forth several methods developed in this that have given usefll results. ccepta?ce of peanut butter is influcnced by the spreadability a i d oil-separation characteristics of the product. For this reason it hsa become necessary to evaluate spreadability and also thCJSe factors influencing spreadability and oil separation. Variouy viscometers, tenderometers, and penetrometers have becri ~ of food mat(%used t o nieasilre t h e tcsture and f l o characteristics rial. However, tlie high viscosity of peanut butter precludes tlic use of thrse iti~truments,except the penetrometer. Penetrometer readings have tieen found t o give a valuable indication of sprcadability . The ,ize distrihution of the particlw in peanut butter influencris the sprwding i.!inrscteristics and the tendency t o oil separation. Standard method. of &ve analysis, followed by microscopic esaminntioil of t tint portion passing a 3’&niVSh screen, are useful in char:ic.Ierizir,g the grind. Hydr8Jgcnatrcivegetable oil is comnionly added in small quan\>;liter t o prevent oil separation. T h e proportion iiiu.-t be carefully rcyulatcd if stabilization is to !:#)ut undue hardening and loss of spreadability. In flip coilritl t:f choosing a method for control of this variable, iodine nui!itici., inelring point, and titer determinations m r e made O I Iwnnut oil containing 0 t o G 7 , hydrogenated oil. tliods proved sufficiently accurate t o dein thr. Ii?thogi.iintcd oil content, it n-as obistry Department, Georgia S t a t e College f o r
served t h a t the melting points of the mixtures ivere distributed over a n-ide temperature range and depended to some estent on thermal history. h satisfactory procedure has been evolved using standardized heating and cooling techniques and the principle of the falling-hall viscometer to determine the thermal flow point. T h e proportion of air incorporated into peanut butter during t h e grinding process may vary widely, even to the estent that it becomes impossible to place the required weight of material in a standard jar. B suitable method for determining air content provides the means for routine checks, as well as for studying the effects of process variables on this property. N o h r and Eysank ( 7 ) determined the air in butter by heating a sample under glycerol in a n evaporatng diPh and collecting the escaping air in an inverted funnel. Air content of ice cream is measured by comparing the w i g h t of a gallon of ice cream mix with the m i g h t of a gallon of finished ice cream (3j. Coffey and Spannuth ( 2 ) determined the air content of shortening by finding the concentration of a n alcohol solution just sufficient to buoy the sample. Loeffler (6) measured the air content of citrus juice by subjecting it to a vacuum and noting the volude of gas evolved. Since the viscosity of peanut butter is not greatly altered by heat, and peanut particles quickly absorb water or alcohol, the mocit satisfactory approach seemed to be to adapt the vacuum estraction technique to this determination. Standiii,d methods that have been found most useful for the of sugar and salt in peanut butter are described. DESCRIPTION OF METHODS
Spreadability. .I representative sample of peanut butter a t 25’ C. is placed in a cylindrical crystallizing dish 8 cm. in dianietcr and 2 cin. high, taking care to leave no air pockets and to have thc top of the butter smooth and level ivith the edge oi the dish. The filled dish is placed on the stagc of a food-t:,ye precision penrtrometer and thc point of the plunger is Ion-ered until it just malics contact with the surface of the sample. The plunger is then released for exactly one niinute and the depth in niillimeters !):netrated kv the plungrr is read from tlie instrument dial. Each nieasuwnicnt should be repeated several times to ensure consistcnt results.
