42
THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
Thus, a certain pulp was found to have consumed 6.03 Ibs. ol chlorine per 100 lbs. of dry material, in the ordinary run of mill practice, excess of bleach being added and the amount of this excess determined. The same washed pulp showed a chlorine factor 2.026, so that the calculated weight of chlorine required to bleach 100 lbs. was 6.078 lbs. Agreement of theory and mill practice could not well be closer. It need hardly be said that bad methods such as negligent washing, excessive temperature, etc., WilI affect the apparent value of K. Whether its value will be the same in every wellconducted mill can be decided only by the extended observations of many competent observers. It would be of great interest to know also whether this method is applicable to pulps of entirely different types made from different woods and by different processes. It is too early to speculate as to whether the fact that K = 3 (at least for certain bleaching methods) has any theoretical significance, but if this value is found to be a general one, a theoretical reason might be suggested. DETAILED DESCRIPTIONOF ANALYTICAL METHOD PREPARATION O F BROMINE SOLUTIQN-Add 8 g. Of bromine to 100 cc. N NaOH solution, agitate till solution is complete, then boil. When cool, dilute to 1 liter. Standardize by adding potassium iodide to a known volume, acidifying with hydrochloric acid and titrating the liberated iodine against 0.1 N sodium thiosulfate solution. The above product remains for weeks without appreciable change in strength and when run into an acid solution is equivalent to a 0.1 N solution of bromine. PREPARATION OF “ACID soLvENT”-Into a flask containing 450 cc. of hydrochloric acid (sp. gr. 1.19) pour slowly 50 cc. of sulfuric acid (sp. gr. 1.84). Mix thoroughly and allow to cool This mixture will generally gelatinize and dissolve pulp in a few minutes. Sometimes, especially when the pulp has not been evenly compressed, it is better dissolved by adding the acids separately and successively in the reaction vessel, allowing the hydrochloric acid to disintegrate the pulp before the sulfuric acid is added. ANALYTICAL PROCEDURE-weigh the dry pulp (0.6 to 0.75 g.) into a dry flask or bottle (about 200 cc.) having a well-ground glass stopper. Add 30 cc. of the “acid so!vent” described above and agitate till solution is complete, or add 27 cc. of hydrochloric acid (sp. gr. 1.19),shake till the pulp is disintegrated, add 3 cc. of sulfuric acid (sp.gr. 1.84),and shake again. It is esvential ab this stage that the solution be quite free from hard, unchanged cores of pulp. When uniformity has been obtained, add a measured volume (20 or 25 cs.) of the alkaline 0.1 N bromine solution, shake well, and allow to stand for 30 min. with occasional gentle agitation. Check the reaction by adding 2 g. of potassium iodide dissolved in about 25 cq. of water and shaking well. Dilute as largely as the capacity of the reaction vessel renders convenient, and titrate with 0.1 N sodium thiosulfate. Toward the end of the titration starch paste may be added advantageously, but disappearance of the blue color is not a sign that the end-point has been reached. There remains a little iodine dissolved in the finely divided cellulose, to which it gives a reddish brown tint. The thiosulfate should be added very slowly toward the end, and each addition should be followed by prolonged and very vigorous shaking. Finally the red tint of the cellulose precipitate disappears, leaving a creamcolored or white suspension. This, the true end-point, can be read within 0.1 cc. after a little practice, and back-titration with 0.1 N iodine solution can be resorted to in case it is overrun. Persistenceof blue or purple spots after all other color has disappeared is due t o the pulp not having been thoroughly disintegrated by the acid solvent. The titration will be untrustworthy in proportion as these spots are large and
Vol. 14, No. 1
numerous; the iodine which they contain leaches out only slowly and somewhat imperfectly-too slo~vlyto make a good titration possible. . CALCULATION O F RESULTS-This is best shown by an actual example. Weight of dry pulp = 0.7722 g. Volume of alkaline bromine solutibn = 20.0 cc. Standardization showed 20 cc. bromine solution = 21.1 cc. 0.1 N NazSzOI Buret reading after titration of pulp= 18.8 cc. 0.1 N NazSaOa Bromine consumed by pulP=4.3 cc. 0.1 N solution
= 0.1798
“Bromine figure’’ = 4.3 and “Chlorine factor” = 4’3
0‘00356 0.7722
loo
-
1.977
SUMMARY 1-The extent to which bromine solutions, approximately decinornial, act on cellulose and on unbleached sulfite spruce pulp has been investigated. 2-It is found that accurate measurements are possible only when the material is brought into solution, e. g., by certain mineral acids, before treatment with bromine. 3-Under these circumstances there is no reaction between bromine and cellulose within 30 min. 4-Reaction between bromine and pulp (containing lignone) seems to proceed in definite steps, one of which is completed within 30 min. &From measurements of this action, a quantity is found which bears a definite and simple relation to the chlorine consumption in bleaching. 6--The method of manipulation is described in detail.
Civil Service Commission Announcements The United States Civil Service Commission has announced the following examinations to fill vacancieq in the Bureau of Standards: Junior aid a t $720 to $840, laboratory apprentice a t $540, laboratory assistant junior grade a t $1000, senior aid a t $900, engineer a t $2800 to $4000, associate engineer a t $2000 to $2800, assistant engineer a t $1 600 to $1800, technologist at $2800 to $4000, associate technologist a t $2000 to $2800, and assistant technologist a t $1500 to $2000. On account,of the needs of the Service, applications will be received until further notice. Papers will berated as received and certification made if the needs of the Service require. On January 11, March 8, and May 17, 1922, examinations will be given to fill the following vacancies in the Bureau of Standards: Junior engineer a t $1200 t o $1500, and junior technologist’at $1200 to $1500. On January 11, 1922, the following examinations will be given to fill vacancies in the Chemical Warfare Service, Edgewood Arsenal, Md.: Chemical laboratorian a t $1200 to $1500, chemistlat”$3600:to $5000, associate chemist a t $2500 to $3600, and assistant chemist a t $1800 to $2500. For further details in regard to these examinations, application should be made to the U. S. Civil Service Commission, Washington, D. C.
Short Course in Ceramic Engineering The regular biennial two weeks’ short course in Ceramic Engineering will be given next January a t the University of Illinois, between the dates of January 23 and February 4. The subjects covered will include elementary physics and chemistry; the origin, classification, winning and refining, and testing of clays; the shaping, drying, and burning of clay products; bodies and glazes; the technology of glass; refractories and refractory products; kiln construction; coal and gas fuels; engines and boilers, dynamos and motors, equipment control; pyrometry; drafting and reading of drawings; and business law. The complete program will be ready for distribution early in January and copies may be secured by addressing the Department of Ceramic Engineering, University of Illinois, Urbana, Ill. The course is open to all who are interested and can be taken to advantage by any one having a common school education. There are no tuition fees.
