July, 1923
I N D USTRIAL A N D Eh’GINEERING CHEMISTRY
to test t h e quality of the Rochelle salt in a blank test, as it has been found t h a t this salt a t times causes a precipitate of copper, presumably due t o the presence of varying amounts of oxalate. The blank test is made by adding a hot mixture of 50 cc. of the Rochelle salt-aIkali solution and 50 cc. of t h e copper sulfate solution t o 400 cc. of boiling distilled water, and boiling for 15 min. in the flask under constant stirring. The solution should not assume a greenish shade, nor should any precipitate appear. Make all determinations with air-dry material, determining the moisture content in a special sample. DETERMINATION O F COPPER NUMBER-Piace about 3 g. air-dry cotton (accurately weighed) in the 1500-cc., round-bottom flask with 250 cc. distilled water, and heat under continuous stirring to the boiling point. Simultaneously, heat separately to boiling 50 cc. of t h e Rochelle salt solution and 50 cc. of the copper sulfate solution in Erlenmeyer flasks of 200-cc. capacity. As soon as t h e water in the large flask boils add hot copper sulfate solution t o t h e hot Rochelle salt solution and pour t h e mixture through the attached funnel into the round-bottom flask. Rinse the two flasks and the funnel with 50 cc. of hot distilled water, bringing the total solution in t h e flask to 400 cc. From the moment when the solution starts boiling, continue the boiling under constant stirring for exactly 15 min., when the stirring should be interrupted and the flask removed. Rinse the condenser, as well as stirrer, with hot water into the flask. Pour the contents of t h e flask onto a Biichner funnel (7 cm.) with double filter paper (S & S 595 has proved very satisfactory) and filter rapidly under suction without allowing the material on the filter t o become dry. Then wash with hot distilled water until the filtrate contains no more copper (potassium ferrocyanide test). Empty the contents of the funnel, including filter paper, into a porcelain dish, rinse t h e funnel carefully with 6.5 per cent nitric acid, and heat the dish on a water bath until t h e precipitate is dissolved. Filter the solution off in the Biichner funnel through filter paper and treat t h e fibrous mass, either on the filter or after removing to the porcelain dish, with a concentrated ammonia solution, which should then be added to t h e first filtrate. By washing with 6.5 per cent nitric acid solution and afterwards with hot distilled water, all copper precipitate is removed. (Test with potassium ferrocyanide.)
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Evaporate the acid filtrate in a porcelain dish and determine the copper by electrolysis. Knowing the exact weight of copper and of bone-dry cotton fiber, t h e copper number can be expressed as the quantity of copper per 100 g. of bone-dry fiber. DETERMINATION OF CELLULOSE: NUNBER-Place about 3 g. air-dry cotton (accurately weighed) and 250 cc. cold distilled water in the round-bottom flask. To this add 100 cc. of cold Fehling solution and 50 cc. of cold distilled water and let the solution stand for 45 rnin. under frequent stirring. Collect the fibrous mass on a Biichner funnel with double filter and wash, first with about 1000 cc. of cold distilled water, and afterwards with hot water. Determine the copper precipitate as outlined above and express the cellulose number in copper per 100 g. bone-dry fiber. The cellulose number subtracted from the copper number as determined above gives the “corrected copper number.” DETERMINATION O F HYDROLYSIS NUMBER4-PlaCe about 3 g. air-dry cotton with 250 cc. sulfuric acid solution of 5 per cent strength in the round-bottom flask, and heat the contents under continuous stirring to the point of boiling. Continue the boiling for exactly 15 min., a t which time neutralize the contents with sodium hydroxide solution (10 g. in 25 cc. water), add 100 cc. hot F’ehling solution and 50 cc. hot water as described under “Copper Number,” and boil for 15 min., after which determine the copper as above. The hydrolysis number is t h e amount of copper obtained with 100 g. bone-dry fiber. Corrected hydrolysis number is found by subtracting the cellulose number from this value. The hydrolysis difference is determined by subtracting the copper number from the hydrolysis number. The determination of a-cellulose is being undertaken by Bjarne Johnsen of the Hammermill Paper Co., Erie, Pa.
HAROLD HIBBERT,Chairman W. F. HENDERSON . BJARNEJOHNSEN W. 0. ~VITSCHERLING I,. E. WISE 4 Schwalbe and Sieber “Betriebskontrolle in der Zellstoff- und Papierindustrie,” 1922, p. 243.
Questions and Answers We have been called upon to obtain certain information regarding apparatus and supplies and give a few examples below for the information of chemists:
One dealer writes us: “A still better stopper than ours can be made either in the United States or abroad, and we shall be glad t o reestablish such a stopper if there is evidence of a reasonable demand. We have had no such evidence in our own recent experience.”
Q.-Are American manufacturers producing graduated glassware of a grade acceptable for certification by the Bureau of Standards?
Q.-What about glass tubing? A,-Pyrex of heavy wall seems to be customarily used for organic combustions. There is satisfactory tubing available for glass blowing, and while a year or two ago there was some unsatisfactory material on the market, this has largely disappeared and the makers generally are anxious to satisfy the demand as to quality, size, etc. Q.-What is the present status of American-made reagent chemicals? Sometimes chemicals are received which bear inordinate amounts of substances which i t would seem ordinary care should eliminate in the process of manufacture. We appreciate what a few manufacturers are endeavoring to do, but it does seem t h a t reagent chemicals, which lie a t the basis of all our work, remain the weakest point in the American line of scientific products. What is the answer? A,-Among some dealers there is the belief t h a t the principal difficulty lies in the desire of the buyer to regard price only. However, the A. C. S. Committee on Guaranteed Reagents and Standard Apparatus will endeavor to obtain the answer to this question in a symposium planned for the Milwaukee meeting. The experience and recommendations of manufacturers, dealers, and users are wanted. Those willing t o contribute t o the discussion are invited to send detailed information t o W. D. Collins, U. S. Geological Survey, Washington, D. C., as early as convenient.
A,--Approximately 90 per cent of the graduated ware received for certification is American-made, and dealers who stock certified ware report t h a t even a larger percentage of their stock has been made in this country. Q.-Can
1000-cc bottles of American manufacture be obtained?
A.-Such bottles are obtainable, though not ordinarily listed according to the metric system, for the reason t h a t they are made from commercial molds. The best of these purchased from reliable dealers are excellent in quality, though not the cheapest, and hold the capacities indicated in the lists. At least one dealer has developed a batch glass formula of a resistant glass from which he has these bottles made. Q.-Can rubber stoppers, satisfactory for combustion and other work, be obtained? Are they as good as those which we formerly imported? A.-Rubber stoppers of all grades are stocked by the trade, b u t unfortunately most of them are purchased by t h e consumer on a cost basis. Not only rubber stoppers, but other rubber goods of a quality equal to the best obtainable anywhere may be had in this country, b d t they must be purchased on a quality basis, preferably after t h e examination of samples. As a rule such goods cost from 30 to 50 per cent more than those ordinarily offered by the trade, although the appearance and the specific gravity may be the same.
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