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I : 2 , it still acts fairly satisfactorily though somewhat slo~vly. When the acid alone is employed it is always necessary t h a t a considerable excess be taken, but the quantity of the latter naturally decreases as the size of the sample increases. With t h e smaller samples, in order t o avoid the use of a very great excess of acid, the same should be diluted, which serves t o increase the volume enough so t h a t all the acid. is not boiled off before complete solution can occur. These points are indicated by the following data:
Sample used Grams 1 3 5 1
5
NITRIC ACID PSED Parts Parts Times acid Water theoretical I 2 6 1 2 4 1 2 3 1 0 8 1 0 6
Total cc. Minutes required of liquid for solution a t start (approximate) 24 7 48 20 60 20 10.5 4 40 10
The use of HzO2,however, produces results greatly superior, in every way, t o those obtained with the nitric acid alone, but especially so in regard t o speed of reaction and excess of acid. Solution occurs so quickly and completely t h a t even small samples can be readily dissolved in a slight excess of acid, it being unnecessary t o have a considerable volume of liquid a t the s t a r t , on account of the rapidity of the reaction. The following results indicate the advantages pertaining t o the use of H 2 0 2 . Practically the same results could be obtained with considerably more dilute acid. Sample used Grams
SOLUTION X~IXTVRE
1
Parts HiXOs 1
3
I
Cc.
Parts water
H?02
2 1
0.5 1.5
Total cc. Minutes required of liquid for solution a t start (approximate) 5 1 10 1
acID-The action of this acid about parallels t h a t of nitric, or if anything, it is somewhat more efficient, for although concentrated hydrochloric is only about one-half as strong as concentrated nitric acid, i t acts with equal speed. Owing t o its lesser concentration a larger volume is required for t h e same equivalent of acid than with nitric, and it was found t h a t owing t o this, a smaller excess of hydrochloric could be used for a given sample than is necessary when nitric is employed; e. g., a j g. sample which was readily dissolved by 4 times the theoretical amount of hydrochloric acid, required 6 times the theoretical quantity of nitric acid t o effect its solution. This behavior with hydrochloric acid was quite unexpected, the writer having always been under the impression t h a t these oxides were practically insoluble in it except in the presence of a reducing agent. The chloride ion apparently acts in the latter rble, free chlorine being given off during the reaction. H 2 0 nacts with hydrochloric acid in exactly the same manner as with nitric. ACETIC ACID-The acid used contained 9 9 . j o per cent HC2H302 and proved t o be a very unsatisfactory solvent for these oxides. I t s action is extremely slow, so t h a t long boiling, with the consequent necessity of a large excess of acid, is necessary in order t o obtain the solution of even a moderate amount of material: e. g , , a r-g. sample was treated with 2 0 times the required quantity of acid, the mixture heated t o boiling, then placed on the steam bath and frequently HYDROCHLORIC
Val. 8 ,
SO.3
shaken; after half an hour the residue was filtered off, the filtrate precipitated with oxalic acid, and the oxalates ignited t o oxides; this oxide did not exceed more than about 0.05 g. in weight. Very peculiarly H202 does not seem t o facilitate solution in this case, repeated experiments using large excesses of the peroxide giving no better results t h a n t h a t above noted. As suggested by Dr. IT. C. Moore, of the Research Laboratory, this behavior may be due t o some reaction taking place between the hydrogen peroxide and the acetic acid itself. S U MM A R Y
I-This investigation has shown t h a t the cerium group oxides are fairly readily dissolved by sulfuric, nitric or hydrochloric acid, and especially so when the concentrated acids are used, although in the case of the latter two. considerable dilution still permits of satisfactory results being obtained. However, it is necessary t o use a considerable excess of the respective acid. and more particularly so if the sample is small and it is required t o dissolve it in concentrated acid. 11-Acetic acid was shown t o be a very unsatisfactory solvent. 111-The use of hydrogen peroxide makes rapid dissolving of the oxides by a very small excess of sulfuric, nitric or hydrochloric acid, possible even in quite dilute solution. With acetic acid, however, the use of hydrogen peroxide does not produce this favorable result. ANALYTICAL LABORATORY, NATIOHALCARBONC O M P ~ H Y CLEVELAHD, OHIO ~
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A METHOD FOR THE DETERMINATION OF ALCOHOL IN THE PRESENCE OF PHENOL' By J
EHRLICH
Received October 27, 1915
It has been repeatedly observed in this laboratory that the usual method of determining alcohol in the presence of phenol by means of distillation from strongly alkaline solution is by no means exact. Notwithstanding the presence of a large excess of alkali, a bromine test on the distillate invariably indicates t h a t a portion of the alkaline phenate always undergoes hydrolysis, allowin;: phenol ?a be carried over. InasinGch as tribromphenol or sodium tribromphenate would be expected t o have a much higher dissociation constant than phenol or sodium phenate because of the brominated nucleus, it was thought t h a t the conversion of the latter into the former would result in decreased hydrolysis and hence obviate the difficulty referred t o above. The method proved t o be practicable. Aqueous solutions (8.6 and 2 0 . 0 per cent by volume) of ethyl alcohol were prepared, a n accurately standardized bottle pycnometer being used for the determination of specific gravity. Throughout the work solutions were measured and the alcoholic distillates weighed a t 2 5 ' C. The j o cc. receiving flask and the 2 5 cc. and j o cc. pipettes mere found to be relatively correct a t 2 5 ' C. 1
Published by permission of the Secretary of Agriculture
Mar., 1916
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
When employing the scheme outlined below t h e following results were obtained: No. 1 2 3
8.674 Phenol Alcohol alcohol added found Cc. Grams Per cent 1 8.6 50 50 3 8.6 10 8.6 50
No. 4 5 6
20.0% Phenol Alcohol alcohol added found Cc. Grams Per cent 1 20.0 50 50 3 20.0 10 20.0 50
I n testing t h e method the phenol was dissolved in
50 cc. strong NaOH solution in the distilling flask t o which t h e known alcohol solution was then added. METHOD
Pipette j o cc. of sample into a 300 cc. flask containing 3 0 cc. water. Make strongly alkaline with an excess of strong NaOH solution so t h a t t h e final volume is about I O O cc. and the odor of phenol is absent. Add glass beads and distil into a 50 cc. graduated flask containing I or z cc. water. The end of t h e condenser or adapter should almost touch t h e surface of t h e distillate in t h e receiver, especially a t t h e beginning of a distillation. A drawn-out thistle tube is serviceable in this connection. The flask is lowered as distillation proceeds. When nearly 50 cc. of distillate have been collected, remove the receiver, dilute with water t o mark, shake thoroughly and pipette 2 5 cc. into another 300 cc. flask containing 30 cc. water. Precipitate the phenol as its tribrom-derivative by adding bromine water, drop by drop, t o slight excess while rotating flask. Without delay add normal “hypo” solution (a few drops will be sufficient) t o decolorize (i. e., t o remove the free bromine excess) and finally add enough strong NaOH solution t o dissolve the white tribromphenol as its phenate, and then a decided excess of alkali. The final volume will be less t h a n I O O cc. After t h e addition of glass beads distil into t h e 50 cc. flask as before, dilute t o mark and determine density by weighing. The percentage of alcohol in this last distillate multiplied by z gives the required figure. For high concentrations of alcohol a I O O cc. receiving flask may be substituted in t h e above method a n d 5 0 cc. of distillate treated and redistilled. For high concentrations of phenol the method is directly applicable since t h e amount of phenol which passes over during the first distillation is small. If the original phenol content is low, the first distillation may be omitted. I n this case the 50 cc. sample plus 30 cc. water in t h e 300 cc. flask is treated directly with bromine water t o slight excess as shown by color; then a d d “hypo,” alkali, etc., as above a n d distil into a 50 or I O O cc. flask according t o alcohol concentration. Samples high in phenol cannot be treated directly in this manner because the bulky precipitate of tribromphenol prevents thorough mixing while adding t h e bromine water, making i t impossible t o perceive when a n excess of bromine is present. The hydrobromic acid formed by the action of bromine on the phenol is neutralized and retained by t h e alkali. CONCLUSION
The method is seen t o be not only accurate in result but extremely simple in manipulation, no filtration or separation being required. The results obtained
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demonstrate t h a t a low concentration of bromine acting during a short period of time has no appreciable effect on aqueous ethyl alcohol a t room temperature. The behavior of methyl alcohol when present in phenolic ethyl alcohol mixtures will be investigated in t h e same way. N. Y. FOOD AND DRUG LABORATORY BUREAUOF CHEMISTRY
THE ANALYSIS OF MAPLE PRODUCTS, VI1 A Volumetric Lead Subacetate Test for Purity of Maple Syrup By J. F. SNELL, N C. MACFARLANE AND G. J. VAN ZOEREN Received August 20, 1915
The fact t h a t lead subacetate produces a heavy precipitate in genuine maple syrup has been utilized in various ways for the detection of adulteration.z I n t h e method here communicated a more dilute solution of this reagent than is employed in any of t h e older methods is gradually added t o the diluted syrup from a burette and the end-point of the titration is determined by means of measurements of electrical resistance in the manner suggested by van Suchtelen and Itano.3 The method in detail is as follows: SOLUTION
A filtered solution of Horne’s lead subacetate of specific gravity 1.033.4 This solution is t o be kept in a bottle connected with a burette and protected from atmospheric carbon dioxide by a soda-lime tube. METHOD
Dilute the syrup with water, boil until t h e temperature reaches 219’ F., and filter through cotton wool. After cooling, dilute I O cc. t o I O O cc. with distilled water and measure 60 cc. of the diluted syrup into a IOO cc. beaker. Measure the electrical resistance using a dip elect r ~ d e . ~Maintaining the temperature constant, add I cc. of the lead subacetate solution from t h e burette, stir well and again measure the electrical resistance. Continue the addition of t h e subacetate in this manner, I cc. a t a time, until I O cc. have been added. Plot the resistances found against t h e quantities of subacetate solution used. If t h e syrup is genuine the results of the plot will be t w o intersecting straight lines. I n the 7 0 genuine maple syrups,G t o which the 1 Presented a t the 51st Meeting of the American Chemical Society a t Seattle, August 31-September 2, 1915. Previous papers of this series: THIS JOURNAL, S (1913), 740, 993; 6 (1914), 216, 301; 8 (1916). 144. An account of the preliminary experiments leading t o the volumetric test is JOURNAL, 8 (1916), 144. given in Paper V, THIS 2 Hortvet, J . A m . Chem. Soc., 26 (1904), 1543; Bureau of Chem.. U. S. Dept. Agric., Circ. 23 (1905); Jones, Vermont Agr. Expt. Sta., 18th Ann. Rept., 1904-6, p. 322; Thos. MacFarlane, Laboratory Inland Revenue Dept., Ottawa, Bull. 120 (1906); Winton and Kreider, J . A m . Chem. Soc., 28 (1906), 1204; McGill and Valin, Laboratory Inland Revenue Dept., Ottawa, Bull. 140 (1907); 228 (1911); Ross, Bureau of Chem., U.S. Dept. Agric , Circ. 53 (1910); Department of Inland Revenue, Ottawa, Circ. G 994.r 8 van Suchtelen and Itano, J. Am. Chem. SOC.,36 (1914). 1793. 4 We make a cold, saturated solution of the subacetate, dilute t o approximately the correct density, filter and adjust to exactly 1.033. as measured b y a hydrometer. 6 A suitable form of electrode is described in a paper by Van Zoeren, published in the Journal of the American Chemical Society, March, 1916. The rest of the apparatus used by us for the measurements of electrical 6 (1913), resistance is described in Paper I of this series (THIS JOURNAL, 740). 6 These syrups were all collected from the makers in the Province of Quebec, 62 in the season of 1915 and 8 in t h a t of 1914
