I N D U S T R I A L d,VD ENGINEERING CHEMISTRY
July, 1926
0.009 for the heavy medium, and 0.004-0.006 for the medium and the lights. Heavy-medium (No. 4) is a very heavy bodied oil, classed by dealers as a heavy oil. If the proposed test is any criterion, their contention is correct. Oils 2, 6, and 10 are from the same refiner and are low as explained above. Oil $1 is known by many automobilists as a cheap but poor oil. None of the tests on this oil showed that such was the case, and if properly used should give as good satisfaction as many of the others. The results by the Conradson carbon residue test, a cracking test, are similar to those obtained by the proposed firepoint carbon test, although there appear more irregularities that are difficult to explain. A subsequent minor comparison between the Conradson and the new test showed that the variations between four or more results on the same oil, with the same method, were greater with the
701
Conradson method than with the new carbon test. Therefore, some of the irregularities in the Conradson results can be attributed to inherent difficulties in the method. If more concordant results could be obtained by experienced analysts with the Conradson test, the same could be said of the fire-point carbon test. Inasmuch as the latter method uses the oil from another well-regulated test, the fire-point determination, does not contaminate the laboratory with smoke and soot as in the Conradson test, or require special exhaust equipment to eliminate such smoke and soot, or is no more difficult of manipulation than the Conradson test, or requires no special apparatus or technic and appears to give results indicative of the carbon-forming propensities of the oils, it is believed that this test should be used as the oxidation test for automobile lubricating oils.
Hydroxylamine Hydrochloride for the Quick Estimation of Acetone’ By Martin Marasco D u POST-PATHB FILMMANUFACTURING CORP.,PARLIN,N. J.
E
XTESSIVE usc’ of acetone by the industries calls for rapid methods of determining the amount of this compound in many liquids and gases. I n a study of different methods, the reaction between acetone and hydroxylamine hydrochloride looked promising and, after a number of experiments, satisfactory results were obtained under the conditions explained in this article. The reaction is expressed by the equation (CHa)2CO NHBOH HC1 = (CH3)zCNOH HC1 f HzO Acetone
+
Hydroxylamine hydrochloride
Acetoxime
+
The liberated acid can be titrated with alkali in the presence of methyl orange. The chance for error in the use of this equation for quantitative analysis, and probably the reason that the acetoxime method is not used more extensively in control work, is due to the fact that the reaction appears to run only to about 94.4 per cent of completion. But by setting certain conditions in the analysis a definite stage of the reaction is reached and the procedure becomes quantitative by standardizing with known amounts of pure acetone. A normal amount of skill in the use of methyl orange indicator enables one to estimate acetone in a sample within 0.0003 gram. Hoepner2 used this reaction in analyzing mixtures containing ethyl alcohol, aldehyde, and acetone. I n his work the presence of aldehyde complicated matters by also reacting with the hydroxylamine hydrochloride to form aldoxime. He solved this difficulty by determining aldehyde and acetone together in one portion and in another portion oxidizing the aldehyde to acetic acid in a known amount of chromic acid. The acetone in the second part was then recovered by distillation and determined separately. Cnfortunately, in Hoepner’s procedure samples were made up with aldehyde and acetone, previously analyzed by the hydroxylamine hydrochloride method. His results are quite concordant, but appear to be misleading in regard to the accuracy of the method. By mixing a neutral acetone sample with neutral hydroxylamine hydrochloride and then calculating the acetone 1 2
Received March 1. 1926. Z. h’ahr. Genussm , 34, 453 (1917).
equivalent from the amount of hydrochloric acid liberated, an outside observer would obtain results 5.6 per cent low. As pointed out by Bennet and D ~ n o v a n ,the ~ reaction between aldehydes or ketones and hydroxylamine is slow. They found it complete only after allowing the mixture t o stand 2 hours or more in a stoppered bottle. By the outlined procedure in nearly neutral aqueous media, the reaction is practically ended in about 5 minutes. When the acid is allowed to accumulate in the reacting zone, the reaction practically stops after it is only partly complete. By keeping the mixture nearly neutral to methyl orange, the reaction proceeds almost to the end, but the quantity obtained, regardless of time and temperature (20° to 35’ C.)l is only about 94.4 per cent of the theoretical yield. h trace of acid very slowly liberated after this yield is obtained is due to slow dissociation of hydroxylamine hydrochloride. Messinger’s method for acetone is well known and widely used. The end point in this titration is more readily seen than when methyl orange indicator is used. The working conditions are much more strict, however, and the procedure4 is more complicated than are those based on the acetoxime reaction. The iodoform reaction is easily disturbed by varying the acetone-iodine ratio, by the acidity of the solutions, by temperature, by time, by insufficient agitation, and by quite a few impurities. Aside from this, the simplicity and the rapidity of the hydroxylamine method make it convenient for routine work in factory operation where extreme accuracy is not essential. Common samples for acetone analysis are those containing methyl or higher alcohols, mixed with various amounts of inorganic salts, gelatin, glycerol, camphor, etc. The sample is pipetted into 0.2 per cent neutral hydroxylamine hydrochloride and the hydrochloric acid titrated with standard alkali. An analysis can be made in a few minutes. Large amounts of alcohols or solvents other than water must not be added with the sample for this would alter the medium in which the reaction takes place, but about 2.5 per cent alcohol in the hydroxylamine solution has no appreciable effect on the results. 8 4
Analyst, 47, 146 (1922). J . A m . Chem. S O L 4,2 , 39 (1920).
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I N D U S T R I A L A N D ENGINEERING CHEiWISTRY
Since camphor is a ketone and forms an oxime, it would seem to prohibit the use of this method of determining acetone in samples containing camphor. This is not the case. I n aqueous or weak alcoholic solutions hydroxylamine hydrochloride (0.2 per cent solution) shows no appreciable reaction with camphor. As the quantity of alcohol in the mixture increases the reaction between hydroxylamine and camphor increases, but even then strong heating is required to get much action. Method for Analysis of Liquids REAGENT-Hydroxylamine hydrochloride (0.2 per cent solution). Dissolve about 12 grams of crystals in about 800 cc. of water. Add methyl orange indicator and titrate carefully with 0 . 1 N alkali to a neutral point. Dilute to 6000 cc. and add sufficient methyl orange to give the solution a golden yellow color. The solution keeps well for 2 or 3 days, but gradually becomes slightly acid and must be neutralized again before use or better, a fresh quantity prepared. It is probably obvious that if one continues to neutralize a slowly dissociating hydroxylamine hydrochloride solution, a point must be reached where only hydroxylamine and sodium chloride remain and the correction factor must increase. But the rate of dissociation is so slow that no appreciable change in the factor is made, even over long periods of time and by many returns of the reagent to the neutral point.
Pour about 400 cc. of the neutralized reagent into each of two 600-cc. beakers. Into one portion pipet a sample containing not more than 0.200 gram acetone. Use the portion in the second beaker as a blank in locating the end point. Introduce the sample below the surface of the reagent, using the pipet as a stirring rod. After the samde is added. titrat; with standard alkali until the solution is nearly neutral. Stir the mixture and w a i t a b o u t 20 seconds. More acid will be liberated. Titrate again. Each time less acid is l i b e r a t e d . After about the third or f o u r t h trial approach the end point very closely, comparing the color with the blank by the aid of light reflected from a white b a c k g r o u n d Stir the mixture occasionally for about a minute. When the solution liberates no appreciable amount of acid in 1 minute the reaction is finished. The larger the sample of acetone the longer it will take to reach this end point. Each cubic centimeter of 0.1 N alkali used in neutralizing acid liberated from hydroxylamine hydrochloride by acetone is equivalent to approximately 0.00614 gram acetone. (The analyst should determine this equivalent by standardizing each fresh purchase of hydroxylamine hydrochloride crystals against known amounts of acetone.) Allowance must be made for any appreciable amount of acid or alkali in the sample.
.
Method for Analysis of Acetone Vapors
Pour 400 cc. of cool, neutralized hydroxylamine reagent into a 500-cc. Erlenmeyer flask connected to another flask as shown in Figure 1. Apply suction to B until about 300 cc. of reagent are drawn from A and replaced by practically a n equal volume of the sample. Close the lines leading from A with clamps and shake d vigorously for about 20 seconds.
Vol. 18. No. 7
Measure the volume of reagent drawn into B and then pour it back into A . Repeat this operation until sufficient acetone to give a reliable titration is obtained. The gases may be aspirated slowly through a column not less than 40 cm. high of cold (15' C.) hydroxylamine hydrochloride solution, as shown in Figure 2. The volume of sample taken is obtained by measuring the volume of water siphoned out of C. The 100-cc. cylinders a and b must be tilted as much as possible after closing the siphon in order to reduce the vacuum in C; otherwise quite a large error may be made in measuring the volume of sample. Experimental
Redistilled bisulfite and commercial acetones were used in the following experiments. I n each case, a 2- to 3-gram sample was weighed in a sealed glass bulb, which was then broken in a stoppered milk bottle containing about 800 cc. of cold water. After thoroughly shaking the bottle and its contents, the broken parts of the glass bulb were ground to bits with a stirring rod and the solution diluted to 1000 cc. Portions of the diluted acetone sample were then carefully analyzed by Messinger's method, following the precautions noted by G ~ o d w i nand , ~ the results assumed to be correct. of Acetone b y B o t h Methods PERCENT ACETONE HydroxylSp. gr. Messinger aminea ACETONE a t 2 0 C. method method Bisulfite .... 99.80 100.0 Commercial 98.90 99.0 99.80 99.6 Recovered commercial 0.7935 99.55 99.5 a Analyzed according to the outlined method, using the acetone equivalent 0.00614.or the theoretical equivalent and the factor 1.057. Table I-Determination
(!:%P
Table 11-Reproducibility of Results b y Hydroxylamine Method YIELDOF 0 . 1 N HCl Acetone Theo- Found by Correcretical titration tion taken REMARKS factor Cc. Cc. Mg.
i:S%
1.055
Av. 103.5 207.2 100.6 100.6
17.85 35.72 17.25 17.25
1,
Factors obtained with 0.2per
1.057) Factors obtained with 0.5 1 052 1: 054 per cent hydroxylamine 1.056 Temperature ofreaction, 25' C. 1.056 Temperature of reaction, 30' C.
1
16.96 33.90 16.32 16.32
Table 111-Effect of Methanol a n d Camphor Meth- Cam- CorrecAcetone anol phor tion taken added added factor REMARKS Mg. Cc. Grams
.. .,
73.9 98.6 98.6 123.2 100.7 100.7
10 10
74.8 74.8
10
98, 74.8
25
123,0
25 25 25
~~
74.8 74.8
.. ..
.. .. .. ..... .
1.055 1.056 1.055 1.055) Saturated 1 060 Saturated 11058
.... .. . .. 0.5 1.0
~ :
1
,096
::%I
:
Small amounts of alcohol have no effect Camphor in absence of alcohol has no effect Incamphor presence of 10 cc. of methanol probably reacts slightl; and causes a decrease in factor Adding 25 cc. of methanol increases correction factor Increasing methanol concentration increases ' camphor reaction
~
~
~
]
Analysis of Aldehydes
Hydroxylamine hydrochloride is also suitable for determining the strength of some aldehyde solutions. Formaldehyde acts like acetone by liberating only about 94.4 per cent of its acid equivalent. Each cubic centimeter of 0.1 N acid liberated i s therefore equivalent to 0.00317 gram formaldehyde. Every precaution for acetone analysis, of course, applies to the method when testing the strength of aldehyde solutions.
