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
rinsings t o t h e solution already in the flask. Make t h e volume u p t o IOO cc., mix thoroughly and transfer a n aliquot of 2 5 cc. t o a z j o cc. glass stoppered Erlenmeyer flask. Proceed as in t h e assay of mercuric chloride tablets, using 15 cc. z N sodium hydroxide solution after first rendering t h e strongly acid solution alkaline. I cc. N/IO iodine solution = 0 . 0 1 2 5 7 g. ammoniated mercury. ( B ) ASSAY O F M E R C U R I A L OINTMENTl-Heat under a reflux condenser about z grams of t h e ointment (accurately weighed into a small flask) with 20 cc. nitric acid until all t h e mercury has dissolved. Pour t h e acid solution through a plugget of cotton into a IOO cc. graduated flask, and rinse t h e fat in t h e flask on t h e water bath two or three times more, first with a small quantity of diluted nitric acid a n d then with 2 0 cc. portions of water. T o this solution, a d d a 3 per cent potassium permanganate solution until t h e former is permanently pink or until brown flakes separate. Decolorize with a 3 per cent solution of ferrous sulfate and finally make t h e volume up t o IOO cc. T o a n aliquot of this solution, add a few drops of ferric alum solution, a n d add a n excess of N/IO KSCN solution. Titrate t h e excess with N/IO HgNOPsolution, a n d finally complete t h e titration with N/IO KSCN. I cc. KSCN solution = 0.01 g. mercury. (c) O I K T M E N T O F R E D M E R C U R I C oxIDE2-This iS assayed by t h e above method using five grams of t h e oint ment. I cc. N/IO KSCN = 0.0108 g. mercuric oxide. ( D ) OINTMENT OF MERCURIC NITRATE is assayed as above described, using IO grams. I n conclusion, t h e author wishes t o t h a n k Dr. Frederick W. Hey1 at whose suggestion t h e work of reviewing t h e standardization of these preparations was taken up. THBUPJOHNCOMPANY KALAMAZOO, MICHIGAN
ELECTROLYTIC DETERMINATION OF MERCURY IN MERCURY OLEATES
2.57
in its present form about two or three years a n d in our hands proves accurate. One would hardly believe quantitative results could be obtained if the mixture is observed just before the electrolysis. The apparatus, a cathode beaker, contains metallic mercury, toluene, hydrochloric acid I O per cent, a n d t h e oleate of mercury. Upon turning on t h e electric current, however, a n d almost as if by magic, this heterogeneous mixture readjusts itself into orderly arrangement, and in a short time the mercury t h a t was combined in t h e greasy oleate lies shining and bright on t h e bottom of t h e cathode beaker ready to be weighed. METHOD-About 0 . 7 t o 1 . 0 gram of t h e oleate is weighed directly into a mercury cathode cup (such as a small beaker, capacity 50 t o 7 5 cc.). T o this sample there are added 15 t o 20 cc. of IO per cent hydrochloric acid a n d 15 cc. of toluene. The cathode cup with its contents is placed within a somewhat larger crystallizing dish or beaker which later can be filled with cold water t o keep t h e temperature of t h e reaction down as desired. After attaching the anode a n d making t h e connections in t h e customary way, electrolysis of this non-uniform mixture is begun, gradually and slowly increasing t h e current u p t o 3 amperes, using about IO minutes t o do it. The current (3 t o 3 . j amperes a t about 8 volts) is then maintained for about 30 minutes, t h e anode rotating at about 800 revolutions per minute. As the electrolysis continues, t h e contents of the cup become heated nearly t o the boiling point of some of t h e constituents, thus melting t h e mercury oleate. It is essential t h a t t h e mercury oleate should melt. If t h e liquid in t h e cathode cup becomes too hot a n d appears a p t t o boil over, i t should be cooled down by pouring water into the crystallizing dish or other surrounding vessel, b u t it should not be cooled down below 60' C. When t h e mercury is all deposited t h e cathode cup is washed out by siphonation in t h e customary way with water, after which t h e metallic mercury is washed with alcohol, dried with ether and finally weighed. LABORATORY O F MERCK &
COMPANY
RAHWAY. N. J.
By B. L. MURRAY Received September 13, 1915
ELECTROLYTIC DETERMINATION OF BISMUTH IN BISMUTH 6-NAPHTHOL
Owing t o t h e greasy nature of t h e numerous oleates of mercury t h e determination of mercury in t h e m by t h e older methods of analysis presents some difficulties. The necessary separation a n d removal of the oleic acid together with t h e tedious determination of mercury by t h e usual precipitation methods may perhaps have deterred some from assaying t h e oleates heretofore. The tendency has been t o take t h e oleates mostly on faith. I n our experience, however, a n effort has been made t o get away from routine a n d endeavor t o make a new application of t h e electrol y t i c determination of mercury, already found so useful a n d satisfactory on other pharmaceutical products. The method t h a t is given below has been in use
By B. I,. MURRAY Received September 13, 1915
This method is not as practical as the one given in the U. S. P In assaying an ointment of yellow oxide of mercury which contains only 0.8 per cent of the mercurial, it was found necessary first to remove the base with ether. I t was then possible t o obtain results approximately correct. i . e. 0.75 per cent. 1
2
Another useful application of t h e electric current in analytic work has been found in t h e determination of bismuth in bismuth @-naphthol. Aside from t h e electrolytic portion i t is only necessary t o ignite t h e compound in order t o remove organic matter and dissolve t h e bismuth oxide and metal thus formed in nitric acid. The resulting bismuth nitrate is then electrolyzed. METHOD-A sample of 0 . 3 gram is weighed into a porcelain crucible a n d heated very gently t o decomposition of t h e @-naphthol. The crucible is finally heated t o t h e full red heat of a Meker burner for 3 minutes t o burn off t h e last traces of carbon. The residue resulting is yellow in color a n d is composed chiefly of bismuth oxide together with a small quant i t y of metallic bismuth. The crucible is placed in a
