T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
I110
extremely doubtful t h a t t h e NO could go completely t o NO2 in his apparatus, in which case results calculated b y t h e formula given would be too low. A C K N 0 WLE D G M E N T S
The authors have h a d valuable assistance, in t h e work on which this paper is based, from Lieut. G. A. Perley, Mr. J. H. Capps, a n d Mr. L. R. Lenhart; M r , A. S. Coolidge performed many of t h e experiments in trying out t h e nitrometer method. BUREAUO F MINES WASHINGTON. D. C.
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A VOLUMETRIC METHOD FOR THE DETERMINATION OF FORMIC ACID OR FORMATES IN THE PRESENCE OF HYDROXIDES, CARBQNATES, OXALATES AND ACETATES By F. TSIROPINAS Received August 16, 1917
This method is based upon t h e well-known fact t h a t formic acid is quantitatively oxidized t o carbon dioxide b y chromic acid in boiling solution, and t h a t therefore every 44 parts by weight of carbon dioxide correspond t o 46 parts of formic acid according t o t h e equation, 2Cr03 3HCOOH = Crz03 3 H 2 0 3C02. APPARATUS-The accompanying sketch shows t h e arrangement of t h e apparatus used: A is a n Erlenmeyer flask of resistant glass with a capacity of about 500 cc.; B is a thermometer for t h e control of t h e temperature of t h e contents of t h e flask; C is a 15-in. Liebig reflux condenser, for t h e condensation of t h e vapors produced during t h e boiling of t h e liquid and is connected b y means of a glass tube' and heavy rubber tubing t o D, t h e gas collector. T h e latter consists of a glass tube, about 1.5 in. in diameter, having a capacity of approximately 600 cc. a n d is graduated in cc.'s; connected t o this gas collector b y means of a rubber t u b e is t h e reservoir E , b y means of which t h e air in t h e collector may be discharged and t h e water level obtained, when t h e COZ gas has been collected in t h e graduated tube. T o prevent t h e absorption of gas by t h e water used for leveling purposes, a I-in. layer of paraffin oil is floated upon t h e surface. REAGENT-50 g. of C. P. sodium bichromate are dissolved in 500 cc. of distilled water, 80 cc. of C. P. concentrated sulfuric acid added a n d t h e liquid boiled for 5 minutes t o expel all dissolved gases; then i t is allowed t o cool t o room temperature. P R O C E D U R E (1)-In t h e absence of other substances which give CO2 when boiled with chromic acid, t h e procedure is as follows: A solution is prepared, so t h a t 5 0 cc. of t h e same will contain from 0.5 t o 1.0 g. of formic acid; 5 0 cc. of this solution are emptied b y means of a pipette into t h e clean Erlenmeyer flask and if alkaline, 2 t o 3 drops of methyl orange are added, a n d t h e solution made acid with dilute sulfuric acid ( I : I ) ; 400 cc. of t h e chromate solution are now
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+
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Vol. 9 , No.
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added and t h e flask attached t o t h e condenser; t h e stopper a t t h e t o p of t h e condenser is removed and t h e reservoir raised until t h e graduated t u b e is filled t o t h e zero mark. The stopper is now firmly replaced a n d a reading is made upon t h e graduated t u b e for correction of t h e air displaced by t h e stopper. T h e reservoir is then lowered a n d observation is made t o assure t h a t t h e apparatus is air-tight. If no leakage is observed, t h e reservoir is again raised t o a level slightly below t h a t of t h e liquid in t h e collector, t h e cooling water turned on, and t h e contents of t h e flask are heated t o boiling. As t h e gas collects, t h e reservoir is lowered from time t o time so t h a t atmospheric pressure is maintained. T h e boiling is continued until t h e volume of t h e gas is practically constant, which requires from 15 t o 2 0 minutes. The flame is now removed and t h e flask placed in a water b a t h a n d cooled until t h e temperature is reduced t o t h a t a t which t h e operation was started; t h e reservoir is brought t o t h e same level as t h e liquid in t h e collector a n d t h e volume of t h e gas noted. A correction is made for t h e air displaced b y t h e stopper a t t h e beginning of t h e operation and atmospheric pressure and room temperature are recorded. T h e volume of t h e gas must now be reduced t o normal barometric pressure a n d a temperature of o o C. according t o t h e following well-known formula,
V ( C - h) 760 ( I at) where VI = reduced volume, V = volume actually found, C = barometric pressure, h = tension of water vapor at temperature t , a = 0.00366, and t = room temperature. Taking t h e results of Guye, t h e weight of I cc. of CO, gas at 760 mm. and a t o o C. is 0.0019768 g., Therefore, t h e number of cc. multiplied by 0.0019768 gives t h e weight of carbonic acid gas generated. This result calculated t o IOO g. of material a n d multiplied by 46/44, or 1.04545, will give t h e percentage of formic acid. Trial experiments with known quantities of C . P. sodium formate (recrystallized from alcohol) gave t h e following results:
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v1 = -
(0.5 Gram Sodium Formate Used in Each Case) CC. OF cog Pressure GENERATED HCOONa Difference TemD. ' C. Mm. Actual Corrected Found Gram 0.4988 -0.0012 163.1 187 25°C. 747 21OC.
26'C. 27'C.
743 743 743
185 188 190
163.7 162.2 163.0
0.5001 0.4955 0,4979
SO.0001 -0.0045 -0.0021
PROCEDURE (?)-In t h e presence of carbonates, bicarbonates, oxalates a n d acetates, t h e following procedure is t o be followed: t a k e sufficient material t h a t t h e formic acid content will range between 2 . 5 a n d 5.0 g. Dissolve in 50 cc. of water, boil a few minutes, make alkaline with N a O H if bicarbonates are present a n d a d d a I O per cent solution of calcium chloride in sufficient quantity t o precipitate all of t h e carbonates a n d oxalates. Allow t h e precipitate t o settle, filter into a 2 5 0 cc. graduated flask, wash thoroughly with boiling water, cool t o room temperature a n d fill t o t h e mark. Take 50 cc. of t h e filtrate and proceed as directed under Procedure ( I ) . Trial experiments with known quantities of C . P. sodium formate mixed with
Dee,
T H E J O U R N A L O F I N D U S T R I A L A N D ENGINEBRING C H E M I S T R Y
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difierent qunntitics of sodium carbonate, oxalate a n d acetate (which is not oxiilizcd by the chromate solution) gave t h e Following results: (0.5 Gram Sodiam Formate Used in Bach Case)
SUUMARI
I- -From t h e above results i t can bc seen t h a t this nil re1i:Il)lc oiic for t h e technical metliod is a n a m i r n detcrmination of iormic acid or format.cs in t h e presence of carlionates; oxalates and :mAntes. 11----An added advantagc is t h a t t h c time required for a n analysis docs not exceed one hour and, furthermore, it rccpircs but little nt.tent.ion; a n d preparations for sulisequent determinations can be made during t h e intervening time. NOTE--T!lorpe in his "Dictionary of Applied Chemistry" calls attention t o a method devised by K u p p a n d published in the ilichiv. der P h a ~ ~ z n z i c243, , 6 9 €or the determination of formates. Kupp uscs sodium hypobromite a s t h e oxidizing agent and not potassium bichromate, as stated by 'Fliorpe. Ih-D"S1'llhL
1111
they outline rather t h a n when i t was extractcd by the Rose-Gottlieb method. 0. Lam's' work on separator slime indicates t h a t a small amount of fat adheres tenaciously t o t h e protein. It would probably adhere none t h e leis tenaciously in evaporated milk or milk powder. The presence of free f a t t y acids would not be expected in any appreciable quantity in condensed milk, but milk powder, on account of its tendency t o develop rnncidity, might have appreciable quantitics, as shown by Eccher.2 Hence, t h e Rose-Gottlieb method, which extracts only neutral fats, might fail to show t h e original fat content of the powder. Hunzikera used dilute acctic acid t o dissolve casein i n condensed milk hefore extracting the f a t with ether. I t has been shown4 t h a t , acctic acid does not react chemically with butt,er f a t . In t h e work recorded here, the errors in t h e Rbse-
CISVICdL IZS.III"TC OF MIIN*"S-QK
M>z,,mz,xs,%wIsc,co.z-sIN
A STUDY OF THE ESTIMATION OF FAT IN CONDENSED MILK AND MILK POWDERS' BY C. EI. UICSTEIIIIIIDA N D 0. L. E u n r s o ~
I t was found b y Rose2 t h a t , if whole milk was treated with ammonia and alcohol, t h e casein was dissolved to such a n extent t h a t the fat could be removed quantitatively by a mixture of equal volumes of ethyl and petroienm ethers. Subsequently, E. Gottlieh' failed t o corroborate the results of Kbse, but found t h a t if he extracted. after t h e treat.ment M o ~ m i i i nR ~ I ~ S ITuuii C (I3ies rcrf~id) with ammonia and alcohol, first with ethyl ether and Hcighl o i tube, w e * all (not iiiciiidicle stepper). 37 em., aboilt~ to obtain more then with petroleusriether, lie was Narrow pari (below rpigotl. 10 mm. outside dia meter. accurate results t h a n he could by t h e procedure outCapacity of narrow pat,to middle line o! spigot. 28 CC. Upper part (above spigot), 2: ~ l m oiiiside . diameter. lined by Rose. Harding and Parkin' claim t h a t reTube must l h v e a tightwittius siass stopper. suits from t h e application oi the Rijse-Gottlieh proNu vent hole in neck. No Eradualianr. cedure to evaporated milk or milk powders show t h a t the frit is not compieteiv extracted. por the fat Gottlieb5 method have been studied and t h e method t h e y proposed to compared directly with a modified method in which determination in evaporated the fat in a a small amount of acetic acid a s a n aid in separating t h e dissolve *he protein in acetic acid mixture of alcohol a n d carbon tetrachloride before f a t from t h e casein, mixtures of petroicunl ether, ~~~i~~ ethyl ether and ethyl alcohol (which are recoverable extracting the fat wit]l petro!eum shaking and centrifuging, rul,ber stoppers Were used for repeated use) and a modified Riihrig tube, have in contact with t h e solvents. The action of t h e been used. seem to be the T h e lwo mixtures, which must be kept separate, are solvents o,, the stoppers used a~ s solvcnts. The by ~ ~ and ~ d i proportions ~ ~for Mixture I are cause of the higher Parkin whcn the f a t was extracted by the procedure 400 cc. of pctrolciim et.her, zoo cc. of ethyl ether a n d I Published by permission of the Secretary of A~riculfiiie. Presented 2 0 cc. Of 95 per cent alcohol' For Mixture the at the 54th Meeting of the A m d e a n Chemical Society in Krolarr City, Mo.. April 10 to 1% 1917.
Chem.. 1888, 100. Lundw. Vir.-Sio., 40 (1892). 1. , T H I S Jouneri, 5 ( I Y I S ) , 1.31.
12. snpdlli. 1
2 2
I
* 6
Milchwirisihofi. Zenlr.. 4% (1913). 691. Arch. Clem. illihros.. 6 (1913). 301. Purduc Uoiv. Agri. Expt. Station. BiillrLin 134 (1909). Bahlman. Tms J o u n n ~ L' .I( I 9 l S ) . 680. U. S. Depi. of Agricnliurc, Bureau of Chemistry, Circular 66 ( I Y I I ) .
