150
THE JOURNAL OF I-VDUSTRIAL A-VD ENGINEERING CHEMISTRY
voi.14, N ~ a.
are of serrice in indicating the rate ol gas production in the pheric pressure of about 730 mm. in- the dough a t a temperdough, which is one of the significant factors in determining ature of about 30” C., it follows that each milligram of carbon baking strength. dioxide will expand the dough 0.59 cc. Thus each cubic The curves also indicate a decided difference in the rate of centimeter of increased volume will represent a t least 1.7 expansion of thc doughs immediately after mixing (no mg. of carbon dioxide. The normally fermented strong previous fermentation) and similar doughs after normally flour dough in expanding 120 cc. thus orcludrd at least 204 fermenting for several hours. The former expanded ~ l o ~ v l ymg. of carbon dioxide and lost about 40 mg, The ratio of gas lost to total gas produced was thus about 40.244, or approximately 1 :6. The corresponding veak flour dough, in occluding 204 mg. of carbon dioxide and expanding 120 cc., lost about 100 mg. of carbon dioxide, a ratio of 100 : 304 or about 2 : 6 . While these ratios are not precise because they are based on certain awmptions, they appear to be of service in establishing significant differences in the properties of such flours. SVbfhfARY
FIG.&-RELATION
OF EXPANSION OF STRONG AND W E A K TO LOSS OF CARBON DIOXIDE
FLOURDOUGHS
during the first hour, more rapidly during the second hour, and continued to expand soniewhat during part or all of the third hour. Doughs normally fermented, on the other hand, expanded more rapidly during the initial period, and exhibited a diminishing rate during each successive period. They always reached their maximum volume sooner than the doughs not previously fermented which were made with the same flour, and tended to collapse or fall more sudden1.i. The relatively slow expansion of the doughs not previously fermented cannot be attributed to excessive loss of carbon dioxide during this time, for reference to Fig. 3 establishes the fact that they aclually lost less carbon dioxide per unit Qf time than the normally fermented doughs. It is not likely that the fermentation rate, and consequently the quantity of carbon dioxide produced in the dough, is reduced in any such proportion as is observed in the expansion of these doughs. This suggests that a part of the carbon dioxide produced at the outset becomes “dissolved” in the dough without effecting an appreciable expallsion of the mass. I n fact, it may be that “ripening” of the dough and its readiness for molding into loares is in part related to the progressive solution of carbon dioxide in the dough during fermentation, Such dissolved carbon dioxide would constitute a reservoir of ga.; largely available for effecting the expansion or spring of dough when placed in the oven for baking, since it would tend to distil into the vesicles already present in the interior of the mass and to extend or enlarge their volume. So far as we are aware, there are no published data relating to the proportion of free or gaseous carbon dioxide in the vesicles and of dissolved carbon dioxide in the dough, and it appears desirable to study the fernientation of bread doughs from that angle to ascertain (a) whether such a progressive solution of carbon dioxide in the dough occurs and (b) whether significant variations exist in the quantity of carbon dioxide dissolved in different doughs. After the dough has fermented several hours and is ready to be molded into loaves, it is probably saturated with carbon dioxide. All the carbon dioxide subsequently proddced will be occluded and serve to expand the mass, or will diffuse or be discharged into the atmosphere. Assuming that the expansion of fermented doughs is accomplished by the occlusion of carbon dioxide resulting from fermentation and assuming further that such carbon dioxide is under atmos-
Strength of flour is apparently determined by the factors which control the rate of carbon dioxide production in, and loss of carbon dioxide from, fermenting dough. The loss of carbon dioxide per unit increase in volume under controlled condition., affords a useful measure of the gas-holding caparity of dough. A procedure is described by means of which such data may be obtained for comparing different flours. It is further suggested that “ripening” of dough during fermentation may be in part the result of solution in the dough of carbon dioxide, which may later become available for expanding the loaf wheii the latter is placed in the oven to bake.
Report of American Commit tee o n Electrolysis The American Committee on Electrolysis, which is made up of representatives of the large national associations of public utility corporations and of the Bureau of Standards, has recently issued its second report. The report includes discussions of design, construction, operation and maintenance of underground structures affected by electrolysis, as well as discussions of electrolysis surveys and apparatus for electrolysis testing. It concludes with an analysis of present European practice relating to electrolysis mitigation, and an outline of researches which the committee consider necessary in this connection. This report is for sale by the American Institute of Electrical Engineers, 33 West 39th St., New York City, at one dollar per COPY. The United States Civil Service Commission has announced examinations for chemical technologist a t $3600 to $5000 a year, associate chemical technologist at $2500 to $3600 a year, and assistant chemical technologist a t $1800 to $2800 a year t o fill vacancies in the Chemical Warfare Service, Edgewood Arsenal, Md. Applicants must qualify in a t least one of the following branches of chemistry : advanced inorganic, analytical, biological, explosives, metallurgical, organic, pharmaceutical, physical, and engineering. Applications must be filed before February 14. Examinations have also been announced for assistant examiner, Patent Office, at $1500 a year, to take place February 8, 9, and 10 and March 22, 23, and 24. Competitors will be rated on the following subjects : mathematics, physics, mechanical drawings, language, technics, and optional subject chosen from one of the following. mechanical engineering, civil engineering, electrical engineering, general chemistry, electrochemistry, and chemical engineering.
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A short course in pulp and paper manufacture is to be given next year a t the New York State College of Forestry a t Syracuse University. The course will include elementary chemistry, elementary forestry, principles of pulp and paper manufacture, pulp and paper mill machinery, manufacture and testing of pulp and paper mill chemicals, manufacture of pulp and paper, practical paper testing, identification of woods and fibers, lectures, talks, and round-table discussion by prominent men in the industry, and inspection trips to a number of the larger mills and mill equipment manufacturers of New York State,
