IOWA STATE COLLEGE JOURNAL OF S CIENCE Published on the first day of October, January, April ~nd July. EDITORIAL BOARD EDITOR-IN-CHIEF, Jay W. Woodrow. AssISTANT EDITOR, Florence Willey Nichols CONSULTING EDITORS: R. E. Buchanan, C. J . Drake, A. H. Fuller, I. E. Mel­ hus, E. A. Benbrook, P. Mabel Nelson, V. E. Nelson, C. H. Brown. From Sigma Xi: E. W. Lindstrom, J. W. Woodrow, 0 . R. Sweeney. All manuscripts submitted should be addressed to Jay W. Woodrow, Physics Building, Iowa State College, Ames, Iowa. All remittances should be addressed to Collegiate Press, Inc., Iowa State College, Ames, Iowa. Single Copies: One Dollar; Annual Subscription: Three Dollars; in Can­ ada, Three Dollars and Twenty-five Cents; Foreign, Three Dollars and Fifty Cents. Entered as second-class matte:- }.anuary 16, 1935, at the postoffice at Ames, Iowa, undrr•thb. a'ct' df..Marcho 3: 187.9 . .·~·.·.·.:. ... .. : . ·. .. .·.· ........... : ... : : :. .. .. .. .. : :.·.::.. .· :·:::::.·. .. .. .. .. .·: .: . .. .. .. : .. ... ·: .··:..· . ·:······.. :-: !.: : . ··: ....... ~·.. ·..· ..·.:·· . .. : :.: :... · .·. .: ·:.: ....... OXIDATIVE DEGRADATION OF SILK. II1 MINNIE LICHTE AND RACHEL El>cAR From the Sections of Home Eccnwmic.s (Textiles and Clothing) and Chemistry, low Agricultural Experiment Station Accepted for publication July 27, 1937 In order to compare the action on silks of permanganate in acidic solution with that in aqueous solution (2) similar plain-woven wild-silk fibroin and silk fibroin (table 1) and the same lead-weighted silk were analyzed for weight, ash, nitrogen, and wet strength, and the same iron­ weighted, tin-weighted, tin-lead-weighted, and zinc-weighted silks for wet strength, after ten hours at 40°C. in fifty volumes of a range of concen­ trations of potassium permanganate, 0.06 M as to sulfuric acid. Before analysis the residual silks were freed of manganese dioxide in thirty min­ utes by fifty volumes of 0.05 M sodium hydrogen sulfite and washed in water until the rinse no longer reduced permanganate. TABLE 1. Analysis of fabrics Wild-Silk pongee Silk crepe 1. Weight, ounces per square 11ard 1.28 2.03 2. Thickness, inch 0.0042 0.0074 3. Yarns (a) Distribution Number per inch, warp 79 287 filling 67 103 Percentage by weight of fabrics, warp 49.l 58.9 filling 49.4 41.2 (b) Count, thousand yards per po'Und, warp 84.6 135.8 filling 70.7 81.4 (c) Twist, number per inch, warp 0 0 filling 0 54*(2) .. 4. Breaking strength of fabric (a) Conditioned, pounds per inch, warp 24(0.9) •• 53(2.3)** filling 21(0.5) •• 32(0.5) •• (b) Wet, percentage of dry, warp 79 72 filling 86 78 5. Elongation at breaking load, percentage (a) Conditioned, warp 27 34 filling 25 28 (b) Wet, warp 33 35 filling 31 35 •Two left-twisted yarns alternated with two right-twisted. ••Average deviation. --- 1 Journal Paper No. J-467 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project 262. [1] 2 MINNIE LICHTE AND RACHEL EDGAR The fabrics were prepared for analysis as before except that the silk fibroins were extracted ·with petroleum ether instead of diethyl ether. The experimental procedures and methods of analysis were the same. TABLE 2. Weight, nitrogen, and wet strength of fabrics afrer ten hours in fifry vol­ umes of 0.06 M sulfuric acid at 40°C. Breaking strength Fabric Weight Nitrogen of wet warp percentage of original pounds fabric per inch A. Iron-Weighted silk crepe 26 B. Lead-Weighted silk crepe 91.2 8.64 19 c. Tin-Weighted silk crepe 19 D. Tin-Lead-Weighted silk crepe 19 E. Zinc-Weighted silk crepe 18 F . Silk crepe 99.9 18.47 33 G. Wild-Silk pongee 99.9 18.30 18 TABLE 3. Weight of fabrics afrer ten hours in fifry volumes of oxidant at 40°C. Potassium Suliuric Wild-Silk Silk Lead- permanganate acid fibroin fibroin Weighted silk molarity molarity percentage of acid-treated 0.0028 0.06 99.5 99.6 96.8 0.0054 99.3 99.3 96.4 0.0154 98.1 98.2 96.4 0.0214 97.3 96.8 0.0337 96.1 96.1 0.0404 94.8 92.3 TABLE 4. Ash of fabrics after ten hours in fifry v olumes of oxidant at 40° C. Potassium Sulfuric Wild-Silk Silk Lead- permanganate acid fibroin fibroin Weighted silk molarity molarity percentage of acid-treated 0.0000 0.06 0.08 0.03 35.81 0.0028 0.16 0.06 36.71 0.0054 0.26 0.11 37.08 0.0154 0.49 0.19 37.36 0.0214 0.68 0.23 0.0337 0.86 0.72 0.0404 0.94 0.85 OXIDATIVE DEGRADATION OF SILK 3 TABLE 5. Nitrogen of fabrics after ten hours in fifty volumes of oxidant at 40°C. Potassium Sulfuric Wild-Silk Silk Lead- permanganate acid fibroin fibroin Weighted silk molarity molarity percentage of acid-treated 0.0028 0.06 99.2 100.1 99.1 0.0054 99.1 98.7 98.3 0.0154 98.6 98.5 94.9 0.0214 97.5 98.0 0.0337 95.5 96.3 0.0404 94.0 93.6 TABLE 6. Wet strength of fabrics after ten hours in fifty volumes of oxidant at 4-0 ° C. Potassium Sulfuric permanganate acid A B c D E F' G' molarity molarity percentage of acid-treated 0.0028 0.06 85 84 79 74 83 91 94 0.0054 77 68 63 47 61 64 83 0.0154 77 26 45 67 0.0214 33 56 0.0337 3 44 DISCUSSION OF RESULTS The similar percentile losses of weight and nitrogen by the wild-silk fibroin and silk fibroin in acidic permanganate (tables 2, 3 and 5) and wild-silk fibroin in aqueous permanganate suggest that superficial solu­ tion of these proteins has occurred rather than elimination of derivatives of different nitrogenous content. The greater loss in weight of silk fibroin than wild-silk fibroin in 0.0214 M permanganate may be explained by the lower ash (table 4). Aqueous (3, 1) and acidic permanganate (4), displaced industrially by hydrogen peroxide as a bleach, are still commonly used in approxi­ mately tenth molar solution for the removal of stains from silk (6). Acidic solutions are shown more desirable for this because all the silks but the lead-weighted retained measurable wet strengths at concen­ trations double those at which their lowest strengths occurred in aqueous permanganate (table 6). This greater loss of strength by the silks and the greater loss of nitrogen by silk fibroin and lead-weighted silk in aque­ ous permanganate may be due in part to the resultant alkali (5, 7). SUMMARY 1. Plain-woven fabrics of wild-silk fibroin, silk fibroin, and lead­ weighted silk were analyzed for weight, ash, nitrogen, and wet strength, and plain-woven iron-weighted, tin-weighted, tin-lead- 4 MINNIE LICHTE AND RACHEL EDGAR weighted, and zinc-weighted silks for wet strength, after ten hours at 40°C. in fifty volumes of 0.0028 to 0.0404 M potassium permanganate, 0.06 Mas to sulfuric acid. 2. The ash of the wild-silk fibroin, silk fibroin, and lead-weighted silk in­ creased slightly with increasing concentration of oxidant. 3. Loss of strength exceeded that of protein. The strength of wild silk fibroin decreased less than that of silk fibroin; the iron-weighted lost less and the tin-lead-weighted more than the lead-weighted, tin­ weighted and zinc-weighted silks which approximated that of silk fibroin at 0.0054 M potassium permanganate. 4. Percentile losses of weight by both wild-silk fibroin and silk fibroin, in aqueous and in acidic permanganate of the same molar concentra­ tion, agreed within experimental error. 5. Percentile losses of nitrogen by wild-silk fibroin and silk fibroin in acidic permanganate, and wild-silk fibroin in aqueous permanganate were the same as the percentile losses in weight, and were less than those of the lead-weighted silk. A greater loss of nitrogen by silk fibroin and lead-weighted silk and a far greater loss of strength by all the silks occurred in aqueous than in acidic permanganate. LITERATURE CITED 1. HUGHES, T. F. 1929. The bleaching of silk. Textile Colorist, 51: 248-252. 2. JOHNSON, R. L., E. c. WALDE AND R. EDGAR 1937. Oxidative degradation of silk. Iowa State Coll. J. Sci., 11: 5-14. 3. MOTAY, T. DU 1874. Procede de blanchment des soies du chene, de l'ailanthe et du ricin et, en general, de toutes les soies dites soies sauvages. French Patent 104, 651, August 17; Bull. soc. chim. (2), 25:95-96 (1875). 4. RISTENPART, E. 1918. Die Permanganatbleiche der Bastseide. Farber-Ztg., 29:37-38. 5. Ross, J . E., R. L. JOHNSON AND R. EDGAR 1936. Degradation of weighted silk fibroin by acid and alkali. Textile Re­ search, 6: 207-216. 6. 1935. Stain removal. Cowles Technical Tips, 3: No. 3, 3. 7. WALDE, E. C., AND R. EDGAR 1935. Degradation of silk fibroin by acid and alkali. Textile Research, 5:460-466. SEED IMPERMEABILITY AND VIABILITY OF NATIVE AND INTRODUCED SPECIES OF LEGUMINOSAE1 MARY ERNE-JEAN HUTTON AND R.H. PoRTER2 From the Botany and Plant Pathology Section, Iowa Agricultural Experiment Station Accepted for publication July 30, 1937 The production of impermeable seeds by plant species in a number of plant families, both cultivated and wild, has long challenged the atten­ tion of botanists throughout the world. The legume family is one of the most important in which seed impermeability is a characteristic condition. Within recent years soil erosion has come to be recognized as a prob­ lem of national importance, the solution of which has an important bearing on the future well-being and prosperity of the people of the United States.