March, 1929
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
systems. A typical save-all installation is shown in Figure 4. I n some mills the fibrous wastes have been reduced to a practically negligible quantity. Research work on both the characteristics and utilization of various chemical wastes was started during 1927 and is being conducted by the mills in cooperation with the state. This research includes: (1) Utilization of sulfite waste liquor (experiments with new process). (2) Recovery and re-use of lime in the sulfate pulping process. (3) Effect of ponding and aeration of sulfite wastes. (4) Recovery of fibrous material in sulfite mill blow pit waste water. ( 5 ) Long-time oxygen demands of sulfite waste liquor, and sulfate pulp mill waste.
At the present time experiments are being conducted with three methods of treatment for creamery waste a t De Forest, Wis. The experimental plant and the creamery are shown in Figure 5. The work is being conducted on a large scale following cooperative studies in the Sanitary Engineering Laboratory of the IJniversity of Wisconsin. Preliminary results indicate the possibility of efficient and economical treatment of the dairy products wastes, one of the major sources of stream pollution in Wisconsin. Municipal Sewage Treatment The problem of municipal sewage treatment is definitely a function of the State Board of Health. Since it is also a factor in pollution control, particularly the matter of continuous and effective sewage plant operation, a brief statement should be made as to the present status of the sewage treatment program in Wisconsin. Of the 206 public and 11 semi-public sewerage systems in the state; 86 have disposal facilities through 100 treatment plants. As a result of the adoption of a policy of routine inspection, a large portion of the plants have been investigated during the past year and recommendations for improve-
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ments or modification of operating methods have been made to secure maximum plant efficiency. A sewage-plant operators’ association has been organized for the purpose of providing a means of exchange of information relative to the successful operation of such plants. I n the disposal of municipal wastes i t is the policy in Wisconsin that cities and villages should assume responsibility for the maintenance of proper sanitary conditions within the areas of their jurisdiction. I n order to secure effective results, therefore, they are expected to provide the necessary sewage-treatment plants and furnish general @supervisionover the operation and maintenance of all installations for the disposal or treatment of sewage and industrial wastes. Summary The stream-pollution control program includes: (1) Activities under a cooperative program adopted with pulp and paper mills and canners’ associations in the development and installation of waste treatment devices to prevent objectionable stream pollution. ( 2 ) Extension of the cooperative policy to include milk products industries. Definite research is being conducted for the development of more satisfactory methods of creamery waste disposal. (3) Enlargement of the scope of sewage-treatment activities to include more adequate supervision over present sewage-treatment plants, and to foster construction of new plants where needed to prevent excessive stream pollution. (4) Systematic pollution surveys of streams as educational and control measures. Considerable progress has already been made under this cooperative program, but the work has just started. Much remains to be accomplished both from the waste utilization and treatment points of view before pollution in Wisconsin can be reduced to a minimum. It is believed, however, that through the mutual cooperation of municipalities, industries, and the public in general, the quickest and most effective results can and will be obtained.
A Contribution to the Preparation of Standard G elati n’O2 J. Harold Hudson a n d S. E. Sheppard EASTMAN
KODAKC O M P A N Y , ROCHESTER, N . Y.
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’SERS of gelatin are finding it important to study this
product more intimately, and this has led to attempts to intercorrelate its physical and chemical properties. I n order that the workers in different laboratories may be able to utilize one another’s results, their measurements must be made upon the same materials, and thus has arisen the necessity for determining specifications for a “standard gelatin.” The writers are of the opinion that the “standard gelatin” should be as nearly as possible of definite chemical composition with its physical properties similar to those of the highest grade of gelatin now obtainable. I n other words, it should be prepared for scientific purposes. The suitability of such a gelatin for photographic or other industrial uses should not enter into the question of its merits. Standards for special purpose materials can be prepared later. The following tentative specifications are suggested: 1 Presented before the Division of Leather and Gelatin Chemistry at the 76th Meeting of the American Chemical Society, Swampscott, Mass., September 10 to 14, 1928. 2 Communication No. 364 from the Kodak Research Laboratories.
1-The gelatin should be prepared from well-limed calfskin, and only the first extract taken at about 54’ C. (130” F.). It should be dried at not less than 5 per cent concentration. 2-The gelatin should be de-ashed to an ash content of not greater than 0.05 per cent. (a) The method of Smitha consists in leaching the gelatin with 10 per cent sodium chloride solution containing 5 cc. of concentrated hydrochloric acid per liter. After the necessary treatments of acid and salt, the gelatin is washed with distilled water until free from chloride. The ash is reduced by this method from 1 or 2 per cent to 0.02 or 0.04 per cent. An analysis of gelatin prepared by this method gave carbon 50.52, hydrogen 6.81, nitrogen 17.53, oxygen 25.15 per cent. ( b ) The recent method of Northrop and Kunitz’ provides for the removal of anions as well as cations. The details are as follows: The gelatin is soaked for 1 hour in M/128 acetic acid a t 5-10’ C . Three washings with cold distilled water are given and then the gelatin is treated with M/50 sodium hydroxide. This also is allowed to react 1 hour, after which the alkali is removed by washing and neutralizing with acetic acid. A last treatment is given with M/128 acetic acid and the gelatin is rapidly washed free of electrolytes. The gelatin is dried by 8
Smith, J . Am. Chem. Soc., 43, 1350 (1921). Northrop and Kunitz, J . Gen. Physiol., 11, 477 (1928).
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washing with alcohol and ether. The specific conductivity of a 2.3 per cent gelatin solution, which had been de-ashed by the above method, was found to be 1.5 X lob4 mho and the pH, 4.84.
3-The gelatin should have a constant isoelectric point, pH 4.7-
4.9, tolerance to be fixed.
4-The gelatin should have a viscosity in the region of 4 centipoises a t 5 per cent concentration or 6 centipoises at 7 per cent concentration, the measurements to be taken at 40 O C. &The jelly strength should be in the region of 300 Bloom grams for a 7 per cent concentration, chilled by melting ice for 16 to 24 hours. 6-The gelatin should be nearly colorless, having a minimum absorption of blue light a t a definite thickness of 5 per cent concentration. 6
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7-The gelatin should be free from grease, fats, or heatcoagulable protein. These specifications are quite tentative, and are intended to invite criticism. I n order to establish final specifications to which the standard material should conform, it is recommended that selected gelatins be completely tested by all laboratories concerned. Then, with definite figures, it will be possible to decide how precise will be the limits for the various properties, what methods are most accurate, etc. I n this way a scale of values may be established which will make the term “standard gelatin” one of definite significance for all laboratories.
Food Gelatin Values Relative to Concentrations’ M. Briefer and J. H. Cohen ATLANTIC GELATINE COMPANY, WOBURN, MASS.
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H E production of gelatin for all purposes has increased rapidly within recent years with corresponding improvement in methods of manufacture and the distribution of its use. By far the largest consumption is in the food industry, which includes such products as ice cream, confections, fancy cakes, biscuits, and so on. For these different uses food gelatin functions in various ways. One or another or several of its physical properties contribute to the quality of the product of which it is a part. This study is limited to the jelly phase of food gelatin with respect t o its behavior a t different concentrations in water, and is intended t o show the values of gelatins of different initial jelly strengths as related to their concentration, so that one mag find from the curves the approximate weight required of any one grade to equal the je& strength of any other grade. The term “grade” refers t o the initial jelly strength as determined by a standard method.2 Functions of Gelatin Properties in Different Foods I n order to appreciate the limiting value of any one or several of the physical properties of gelatin we should consider briefly the functions of those properties. Naturally, the jelly phase is useful only when in the jelly state. The value of a gelatin, as expressed by the jelly strength, applies only to such products as are used, in their final form, as a chilled jelly. Gelatin jelly desserts and ice cream are examples of products depending on the jelly phase of food gelatin. On the other hand, soft marshmallow confections, because they are not in the state of a chilled jelly, depend more on the viscosity of the gelatin. Here we require a condition capable of supporting a network of foam walls and a high degree of moisture retention. Still another type of product is the hard candy or gum candies, in which the ’ gelatin is in a dry or semi-dry state. Neither jelly strength nor viscosity I alone plays the important role. Very likely “jelly consistency,”3 which is a compound property of jelly strength and viscosity, as well as solubility and i t s c o - r e l a t i v e property, water abIO
1 Presented under the title “Relations of Gelatin Concentration t o Jelly Strength” before the Division of Leather and Gelatin Chemistry a t the 76th Meeting of the Arnericdn Chemical Society, Swampscott, Mass., September 10 t o 14, 1928. * IND. END.CHEM., 16, 310 (1924). 8 Briefer and Cohen, Zbid., 20, 408 (1928).
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sorption, all combine to contribute to the quality of these candies. As a protective colloid, gelatin functions in a special way. I n this case the question of total solids is to be considered. With respect to “jelly consistency” a high-grade food gelatin may require only 3 per cent solid gelatin t o be equivalent to as much as 8 per cent of a low-grade gelatin but the protective colloid value is decidedly better with the gelatin having the larger quantity of total solids because of the increased dispersity possible in the denser medium. From these considerations it follows that the choice of gelatin for any particular use is a proposition, not simply of high or low grade, but of its power to function in a special way suitable to the purpose in hand. Experimental Procedure The experimental work was done with a Bloom gelometer,2 using two different sized plungers. Solutions were made up of air-dry gelatin of grades from 60 to 250 Bloom grams2andiarying in-concentration from 1to 10 per cent, or in any case to the lowest concentration limit of the testing apparatus. The pH was noted and it was found that above a certain minimum concentration, varying somewhat with the grade, the pH had no appreciable effect on the jelly strength. The various samples were tested a t different times against known standards, and finally the entire group in each case was prepared a t one time and chilled all together, in the same water bath, a t 10” C., controlled to a differential of =F 0.1” C. The entire work is in good agreement and the curves (Figures 1 and 2) represent fairly the characteristics
