Affiner votre recherche
Résultats 1-10 de 23
Birds collected during the Whitney South Sea Expedition | Birds of the Whitney South Sea Expedition | Northern shore birds in the Pacific Texte intégral
1943
Stickney, Eleanor H
Nota sôbre a dosagem iodométrica da vitamina C nos frutos cítricos Iodometric determination of vitamin C in citrus fruit juices Texte intégral
1943
Gilberto G. Villela | José Danilo Pecci
<abstract language="eng">Ascorbic acid was determined in pure aquous solutions and in citrus fruit juices by iodometric, dichlorophenolindophenol and iodate methods. More constant values were obtained with iodate and Tillmans methods. Iodate is preferable owing to the stability of solution and the simplicity of the method. In the analysis of citrus juices the iodate method proposed by Ballentine is very accurate and suitable for routine work (Table I and II). Recovery experiments recorded in Table III show that the results are reproducible. The averages obtained for some fruits are shown in Table IV. Lemon: 45,4 to 67,3; orange: 28,0 to 60,8; lima: 25,2 to 38,2 and mandarine: 32,0 to 59,3. Values expressed in mg per 100 cc. of juice.
Afficher plus [+] Moins [-]Proper Starching Technique Texte intégral
1943
Kaswell, Ernest R.
In view of the widespread application of starches for the sizing of yarns and fabrics, and, in particular, the pres ent scarcity of starch, it is imperative that a maximum economy be attained in the use of this important raw ma terial. The following study was made for the specific pur pose of improving the technique in laundry practice. However, it is believed that disclosure of the relationship between certain variables and fabric stiffness will be of assistance to textile men in general. It was found in this study that a linear relationship between the amount of starch and weight of material such as is frequently used in determining the proper amount of starch does not hold. By proper use of graphs the correct amount of starch for any given weight may be determined.
Afficher plus [+] Moins [-]Controlled Molecular Length Texte intégral
1943
Sookne, Arnold M. | Harris, Milton
The mechanical properties of films prepared from a series of fractions of cellulose acetate, varying widely in molecular chain length (DP)² were determined. A frac tion of DP 30 would not form a coherent film; fractions of higher DP showed a rapid improvement of mechanical properties with increase in DP, but above 150, further improvement was slight. A close correlation was found between the results of folding endurance and ultimate elongation measurements. These properties are more sensitive than tensile strength to changes in DP and to heterogeneity with respect to DP. Investigation of the properties as a function of both weight-average and number-average DP indicated that at any given weight- average DP, the fractions are superior to the blends and furthermore, those blends which contain fractions of low DP are inferior to those which do not. In contrast, at any given number-average DP within the range studied, the properties of the fractions and all of the blends are approximately equal.
Afficher plus [+] Moins [-]Lactacidemia: métodos de dosagem do ácido lático Texte intégral
1943
Maria Isabel Mello
<abstract language="eng">A critical study of three methods for the determination of lactic acid (EDWARDS, MENDEL & GOLDSCHEIDER, MILLER & MUNTZ) is presented and some modifications are proposed. It was shown t hat more accurate results could be obtained with Edward's technic when an Iena glass filter is connected with the absorption tube. Before the dropping of the permanganate solution it is necessary to pass a current of air through the reaction flask to avoid the oxidation of the non-lactic acid substances which interfere with the reaction. The absorption tube must be maintained at 18°C during the destillation and the titration of the bisulphite binding aldehyde at 4°C. When the sample contains more than 5 mg it is useful to work with greater quantities of the bisulphite. More permanganate is consumed when the lactic acid concentration is higher. The sensivity of the method permits the titration of 0.04 mg to 5 mg of lactic acid in the sample. The calculated error of the method gave 0.018 % and the normal values for blood determined in 20 human cases averaged 10.30 mg per 100 ml (Table VI). MENDEL and GOLDSCHEIDER'S method was modified in the following details: Somogyis deproteinization was performed instead metaphosphoric acid as in the original method; to avoid the evaporation of the acetic aldehyde during the heating time with sulfuric acid a special glass stopped tube is proposed (Fig. 2). The reaction with sulfuric acid and veratrol is performed in an ice bath. Blood proteins precipitants were tried and Somogyi's lattest tecnic showed better results (Table V). Colorimetric readings were done in the PULFRICH photometer using filter S 53 and a 10 mm cup. The method is accurate within an error of 0.23 % and samples of 5 to 70 microg. could be easily determined. Normal values for human blood averaged 10.78 mg per 100 ml. More accurate results were obtained with the technic of MILLER & MUNTZ. Slight modifications were introduced: deproteinization with copper sulfate and sodium tungstate; satured p-hydroxydiphenyl solution according to KOENEMANN which is stable for 5 months when stored in the ice-box. Using the PULFRICH step-photometer the error is 0.17% with samples varying from 0.1 to 10 microg. of lactic acid. The filter employed was S 57 with the 5 mm cup. The method was adapted to 0.1 ml of blood. Normal values for human blood gave an average of 10.58 mg per 100 ml.
Afficher plus [+] Moins [-]Plantae Colombianae. – III: Investigationes Specierum Saurauiae: Locus Primus Plantae Colombianae. – III: Investigationes Specierum Saurauiae: Locus Primus Texte intégral
1943
Schultes Richard Evans
<p class="MsoNormal" style="margin-bottom: .0001pt; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: ">As a result of preliminary studies towards a revision of the American species of Saurauia, I have found it advisable to present the following notes on new or otherwise interesting species from Colombia. Mosf of the classical collections of New World species. of Saurauia are preserved in European herbaria. These are at present unavailable for study. For this reason, I have thought it valuable to call attention to recent and ample collections which have either been compared with authentic material or which have been critically determined. It is with pleasure that I thank Miss Inés de Zulueta and Mr. Gordon W. Dillon for their beautifully executed drawings of several</span><span style="font-size: 12.0pt; font-family: "> of the new species herein described</span><span style="font-size: 10.0pt; font-family: " lang="EN-US">.</span></p><br> <p class="MsoNormal" style="margin-bottom: .0001pt; line-height: normal; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 12.0pt; font-family: ">As a result of preliminary studies towards a revision of the American species of Saurauia, I have found it advisable to present the following notes on new or otherwise interesting species from Colombia. Mosf of the classical collections of New World species. of Saurauia are preserved in European herbaria. These are at present unavailable for study. For this reason, I have thought it valuable to call attention to recent and ample collections which have either been compared with authentic material or which have been critically determined. It is with pleasure that I thank Miss Inés de Zulueta and Mr. Gordon W. Dillon for their beautifully executed drawings of several</span><span style="font-size: 12.0pt; font-family: "> of the new species herein described</span><span style="font-size: 10.0pt; font-family: " lang="EN-US">.</span></p>
Afficher plus [+] Moins [-]A comparison of carotene, protein, calcium, and phosphorus content of buffalo grass, Buchloe dactyloides, and blue grama, Bouteloua gracilis
1943
Langham, W. | McMillen, W.N. | Walker, L.
The moisture, carotene, crude protein, crude ash, calcium, and phosphorus content of buffalo grass (Buchloe dactyloides) and blue grama (Bouteloua gracilis) have been determined at intervals during the period from May, 1939, to November, 1941. Moisture, crude protein, carotene, and phosphorus were high in both grasses during the early stages but decreased rapidly as the plants approached maturity. Calcium was quite variable in both varieties throughout the growing season. The average of analyses of all samples taken after frost showed buffalo grass to be much higher in crude protein, crude ash, calcium, and phosphorus than was blue grama. This has been interpreted as indicating that buffalo grass makes better winter pasture and suffers less loss of nutrient material as a result of wintering or leaching than does blue grama. The chemical composition of buffalo grass seems to be affected less by previous clipping than that of blue grama. As a factor in pasture management for the Southern Great Plains area, the effect of frequency or intensity of grazing on chemical composition may be insignificant in comparison with the effect of the variability of weather conditions and grazing on total yield of grass.
Afficher plus [+] Moins [-]Minor element studies with soybeans. I. Varietal reaction to concentrations of zinc in excess of the nutritional requirement
1943
Earley, E.B.
The deleterious substance responsible for the death of the soybean plants attempted to be grown in the greenhouse during the fall of 1937 and spring of 1938 was zinc which had dissolved from the nutrient solution pump. There exists a distinct varietal variation among soybeans in reaction to approximately 0.3 p.p.m. (2.3 mgms per plant) of zinc in a slightly acid nutrient solution when plants are grown in crushed quartz. Hudson Manchu will successfully tolerate 8 andperhaps 12 times the external concentration of zinc as will Peking. The mechanism of varietal reactions of soybeans to zinc was not determined, although differential absorption and tolerance are discussed in this connection. The reaction of soybean varieties to zinc showed no correlation to percentage of oil or protein of the seed. Likewise, there appeared to be no consistant relationship between color of seed and plant reaction to zinc. Among the varieties studied, with the exception of Biloxi and Virginia, early maturity and resistance and late maturity and susceptibility appear to be associated. Also, with regard to size of seed and varietal reaction to zinc, it may be stated that the most resistant varieties were the largest seeded ones, while the most susceptible varieties were the smallest seeded ones.
Afficher plus [+] Moins [-]Chemical, Mitscherlich, and Neubauer methods for determining available potassium in relation to crop response to potash fertilization
1943
Olsen, S.R. | Shaw, B.T.
A study was made of the crop response to potash onsix Ohio soils from 1939 to 1941. Corn was grown each year. A definite crop response was shown each year on the Clermont and Miami soils, a slight crop response was found on the Wooster and Mahoning soils, and none on the Muskingum and Brookston soils. The available potassium in each soil was determined by chemical, Mitscherlich, and Neubauer methods. All methods agreed in placing the soils in the same order with respect to available potassium as indicated by field response. The Mitscherlich and Neubauer methods gave a somewhat better differentiation of available potassium than the chemical test in the two soils which showed the most crop response to potash additions. The Neubauer method was used to study the amount of nonexchangeable potassium released from the silt fractions. Only three soils, the Clermont, Wooster, and Brookston, were examined. Significant amounts of potassium were removed by the rye seedlings from each fraction. As the particle size decreased, the amount of potassium removed increased. The lower the exchangeable potassium in thie soil the greater was the proportion of potassium taken up from the silt fraction.
Afficher plus [+] Moins [-]Reducing the error in infiltration determinations by means of buffer areas
1943
Duley, F.L. | Domingo, C.E.
A method is described for determining the infiltration capacity of a soil by using large plots protected against loss of applied water through lateral seepage. Approximately square 0.016-acre plots were laid out on a 4.6% slope and surrounded by metal borders sunk into the ground to a depth of 6 inches. Surrounding the plot was a border space which had the same treatment as the plot itself. About 4.5 feet outside the plot lines a trench was dug and water run through this until a belt of soil 7 to 10 feet deep around the plot was saturated. This served as a buffer area through which water and air could not pass laterally from the plot area on which infiltration tests were to be made. The plot together with the border area was spaded and covered with straw and then sprinkled by means of a multiple set of stationary sprinklers. The runoff from the 0.016-acre plot was collected and measured and the total intake and infiltration rate determined. A small plot, 16 by 72 inches, was placed in the middle of the 0.016-acre plot area and given the same preparation and straw treatment. The application of water and runoff were determined by a special system entirely separate from that used on the large plot. The results show that the intake of water on the large plots and on the small plot within were similar. Other of these small plots were placed in the open field where they had no water applied to the surrounding soil and no wet buffer belt to prevent lateral movement of air or water. The intake on these isolated small plots having no prewetted border protection was 75% greater than for the large plots. These results indicated that lateral movement of water had allowed these small plots to take in more water than would be possible if it were raining over the entire surface. Since the large plots were protected against lateral movement of water beneath the surface, the results on these plots should represent about what would be the intake possibilities if rain were falling over an entire watershed having the same soil and surface conditions as did these plots. The method used on these large plots might provide a means for determining with a fair degree of accuracy the infiltration capacities of a wide range of soils and surface conditions under natural rainfall. The method might be made to supplement the use of small plots when total intake capacities rather than the effect of specific surface treatments on intake are desired.
Afficher plus [+] Moins [-]