Determination of Water EMOD V. MIGRAY, 1, Sashegyi-fit 11, Budapest, Hungary
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wajhed with ether, dried in a vacuum, and weighed. The xylene distillate IS poured through the filter, and all the copper sulfate is brought onto the filter by rin.;ing the flask with benzene. Then after washing it with ether the filter tube is dried in an evacuated desiccator and weighed. As the liquid runs through the filter very rapidly, some care is required to keep the pad covered with liquid until filtration is complete. If a high vacuum is used, the weighing can be made after 10 to 15 minutes. The increase in weight gives the weight of water.
N THE determination of water one of the following meth-
ods is usually applied: (1) the sample is dried and the water content calculated from the loss in weight; (2) the sample is dried in a htream of dry gas, the gas stream is passed through a weighed mater absorbent-for example, anhydrous calcium chloride-and the increase in weight of the latter is calculated as water; (3) the sample in a distilling flask is mixed up with a liquid that boils above 100" C. and is immiqcible with n.ater-for example, xylene-then the mixture 1. distilled, the distillate being received in a graduated vessel from which the distilled-over water is read off directly (Marcusson procedure). All three methods have both advantage, and drawbacks. The following procedure is an extension of the distillation method, and it has the advantage in that small quantities of mater can be determined accurately, even when the material contains only a few tenths per cent of water.
Rapid drying of the filter can also be accomplished in the following manner: To a tall glass cylinder, such as is used for taking the gravity of liquids, provided with a two-hole stopper, sulfuric acid is added to a depth of about 5 cm. A capillary tube passes through one hole of the stopper and dips into the acid; the filter is inserted in the other hole and adjusted so that the lower end of the filter tube is preferably 15 to 20 cm. above the acid. The upper end of the filter tube is connected with a suction pump and evacuated. Only a very little air is permitted to enter through the capillary, so that the filter will stand under a vacuum. With this arrangement other precipitates can also be dried quickly a t lower temperature. In using this drying device the author finds that it is sufficient to wash the copper sulfate with benzene only, thus dispensing with the frequent use of ether. When a precipitate is dried in this manner, great care must be taken that evacuation does not occur too suddenly; otherwise a part of the precipitate may be carried out with the stream of air. In order to attain rapid and complete drying, it is necessary that only a little air be admitted through the capillary, so that the filter will be under a vacuum.
Procedure Briefly the method involves (1) distillation of the material with xylene or toluene, (2) dehydration of the distillate with a weighed quantity of anhydrous copper sulfate, filtration, and washing of the copper sulfate with benzene and ether with subsequent drying in vacuo, and (3) calculation of water from the increase in weight of the copper sulfate. The determination is carried out as follows:
A weighed sample of 0.5 to 500 grams, depending upon the expected water content, is mixed with 100 to 200 ml. of xylene in a distilling flask. The flask is connected with a straight (Liebig) condenser and the distillate is caught in an Erlenmeyer flask provided with a glass stopper and containing 0.5 to 5 grams of anhydrous copper sulfate. It is convenient to keep the anhydrous copper sulfate in a weighing glass in a desiccator and to determine the amount introduced into the flask by difference
It is convenient to collect the xylene (toluene), benzene, and ether separately, so that they may again be used as the occasion arises. The ether and benzene must not leave a weighable residue on evaporation to dryness. I n contrast with the Marcusson method in which the xylene has to be s a t u r a t e d with water, all liquids ' must be d e h y d r a t e d with anhydrous copper TABLEI. RESULTS FOR WATERIN VARIOUSORGANIC PRODUCTS sulfate. The method is applicable to the determination Method as Described Comparison Method CuSOa Water Water Method of water in any product which loses its water Material Sample Taken Found Sample Found Used a t 110' to 140' C. and yields no other volaGrams Grams % Qrams % ' tile compounds that act on copper sulfate or 500.0 0.0185 0.0'37 Marcusson method not applicable; Machine oil are insoluble in benzene and ether. The deoil is dried by heating. 3.2360 0.1262 3.9 100 3.8 Marcusson Crude oil termination can be carried out either as a macroCrude oil emulsion 0,6130 0.5596 91.3 10 90.0 Marcusson Vehicle grease 4.3685 0,2230 5.1 20 4a5 Marcusson or a micromethod. 3.1765 0.0670 1 . 8 10 Marcusson Machine grease Table I gives a few determinations of water, Leather-finishing oilb 2,7255 0,0764 2.8 50 2.6 Marcusson 5.3280 2.95 d and for purposes of comparison includes results Leather-finishing oil c 5,6926 0,0365 1.73 4.2620 1.85 d Lardonat X (fatty alobtained by other methods. It will be noted coho1 sulfonate) 2,3135 1,1465 49.55 l5,O 50 Marcusson that the results b y the two methods a r e i n 4.6180 53.4 Starch 0,5615 0.0910 16.2 50 16 Hoffman good agreement. The Marcusson method yields 5.0250 16.25 d somewhat lower figures than the one described a Not determinable. b Su!fonate,d Sulfonated neat's-foot train oil with oil with 40% 10% mineral neutral oil. oil. herein, especially when the sample i s s m a l l . d Mixed with sand and dried a t 105' C. The Hoffman method for the determination of water in starch is very similar to the Marcusson procedure; in place of xylene a mixture of 400 cc. in weight. The distillation should be carried out as rapidly of oil of turpentine and 10 cc. of xylene to 50 grams of starch as possible (boiling st'one or glass beads) and as much as possible is used, The contentof containing organic of the xylene should be distilled over. At least 50 cc. of xylene solvents-for example, some fatty alcohol sulfonates-cannot should be distilled off; in instances xylene is poured back into the distilling flask, taking care to avoid the loss of any be determined by drying, but correct results are obtained by the distillation method. The frothing of fatty alcohol sulcopper sulfate therebjr-it is more suitable to use fresh xyleneand the distillation then continued. The distillate is shaken fonatesand highly sulfonated oils during distillat,ion can be well with the copper sulfate in the receiver and filtered by means avoided by the addition of dry sodium chloride to the disof a small tube filter. The filter consists of a tube 10 to 15 mm. in diameter and about tillation flask. 10 cm. long, constricted at the bottom to provide support for RECEIVED .lugust 6, 1934. a small filter plate on which a filter pad is placed; the filter is 348
