Specific Gravity of Latex and of Rubber

1940 ◽  
Vol 13 (3) ◽  
pp. 485-504
Author(s):  
H. Fairfield Smith
Keyword(s):  
Specific Gravity ◽  
Rubber Content ◽  
Rubber Phase ◽  
Almost All ◽  
Good Agreement

Abstract From observations on specific gravity and dry rubber content of latex, of centrifugal concentrates, and of latex-water mixtures, a number of attempts have been made to deduce the specific gravity of the rubber phase. Such estimates, after allowing for criticisms and adjustments which have been put forward, range from 0.901 to 0.914. But writers have made no attempt to consider how their calculations would be affected by treatments of the latex such as ammoniating and centrifuging, by different ways of evaluating the results, and by variations in temperature. When consideration is given to such matters almost all observations published during the last 20 years are found to be in good agreement one with another. Specific gravity, the ratio of the mass of a certain volume of a substance, at temperature t2, to that of the same volume of water, at temperature t1 is commonly designated dt2t2. To avoid excess affixes, when the temperature of the substance does not require to be stated, let:

The Specific Gravity of Preserved Latex

1935 ◽  
Vol 8 (3) ◽  
pp. 448-455
Author(s):  
Edgar Rhodes
Keyword(s):  
Specific Gravity ◽  
Trade Association ◽  
Rubber Content ◽  
A Value ◽  
Straight Line ◽  
De Vries ◽  
The Subject ◽  
Rubber Phase ◽  
Content Range ◽  
Good Agreement

Abstract The Journal of the Rubber Research Institute of Malaya, 5, 234 (1934), contained a paper on the specific gravity of preserved latex written by the writer of this note. The paper has recently been made the subject of constructive comment by de Vries. As a result of the examination of 852 samples of preserved latex, a specific gravity/dry rubber content table was derived for preserved natural latices, and the dry rubber content range covered was wide enough to include natural unconcentrated latex in all the phases in which it is likely to be required by or become available to the commercial user. By the unavoidable expedient of extrapolation from the experimental results, a value of 0.902 was also derived for the specific gravity of the rubber phase in preserved latex. This value was in good agreement with the figure of 0.901 obtained by Scholtz and Klotz for “rubber” in fresh latex. On the other hand, de Vries, working with fresh latex had previously derived a value of 0.914 for the specific gravity of the rubber phase, and the specific gravity table used by the Rubber Trade Association of London for preserved latex gives on straight line extrapolation a value of 0.912. It seemed that the value indicated by the work of De Vries and that deduced from the table of the Rubber Trade Association were probably rather high, and certain experiments with centrifugal concentrated and centrifugal concentrate-skim mixtures were cited which provided some confirmatory evidence of this conclusion.

The Specific Gravity of Preserved Latex

1935 ◽  
Vol 8 (2) ◽  
pp. 284-296
Author(s):  
Edgar Rhodes
Keyword(s):  
Specific Gravity ◽  
Disperse Phase ◽  
Additional Data ◽  
Trade Association ◽  
Significant Feature ◽  
Rubber Content ◽  
De Vries ◽  
Rubber Phase

Abstract The literature on latex contains a number of references to the specific gravity of fresh latex, but published information on the specific gravity of preserved latex in the condition In which it reaches the consumer appears to be practically non-existent. de Vries and Scholtz and Klotz investigated the specific gravity of undiluted fresh latices of various dry rubber contents, and from their results each deduced the specific gravity of the disperse or rubber phase. The average specific gravity of the rubber globule as deduced by de Vries is 0.914. Scholtz and Klotz's value for the disperse phase is 0.901, which is appreciably lower than that of de Vries. Although. the published literature contains no references to the specific gravity of commercial preserved latex, the Rubber Trade Association of London gives a table of values in its latex contract forms, but details are lacking as to the total number of experimental observations which the table represents. A significant feature is that, by extrapolation of the dry rubber content values to 100 per cent, after the manner of Scholtz and Klotz, the figures obtained for the specific gravity of the rubber disperse phase is 0.912, which agrees fairly well with that of de Vries for fresh latex, and which is considerably higher than that of Scholtz and Klotz. In view of the paucity of information available on the specific gravity of preserved latex, it seemed desirable to obtain additional data and incidentally to make a further check on the published values for the specific gravity of the rubber disperse phase.

The State of Polydispersion of Hevea Latex. I

1946 ◽  
Vol 19 (1) ◽  
pp. 176-186
Author(s):  
J. H. E. Hessels
Keyword(s):  
Protein Content ◽  
Hevea Brasiliensis ◽  
The State ◽  
Rubber Content ◽  
Rubber Latex ◽  
Latex Particles ◽  
Rubber Particles ◽  
The Subject ◽  
Points Of View ◽  
Good Agreement

Abstract The rubber particles in the latex of Hevea brasiliensis are present in the form of a polydispersion, and their diameters lie within the range of 0.1 to 3 microns. The rubber hydrocarbon itself is composed of a mixture of macromolecules of different degrees of polymerization. Rubber latex is, therefore, a system which is at the same time both polydispersed and polymolecular. It is well known that the degree of dispersion of a substance governs to a great extent certain properties of the substance. Moreover, astonishing as it may seem, in the great number of investigations which have been made of the composition and properties of latex and crude rubber, almost no attention has been paid to the part which may be played by the dimensions of the latex particles. However, in an investigation concerned with the centrifugation of latex, Loomis and Stump have called attention to this possibility, and in a study of latex obtained by fractionation, and in which the majority of the latex particles were of large dimensions, McGavack came to the conclusion that the protein content is proportional to the surface area of the globules. This limited knowledge of the subject seemed to warrant a more thorough study of the problem, which is of fundamental importance both from the theoretical and practical points of view. The investigation as a whole divided itself into three essential parts: (1) separation of latex into fractions containing particles of different sizes, and measurement of the state of dispersion in these fractions, (2) a study of the relation of these fractions to the composition of the rubber, i.e., the relation between the content of nonrubber components and the size of the latex particles, and (3) a study of the changes in the properties of the rubber hydrocarbon with change in the size of the latex particles. The latex used in this investigation was ordinary latex, containing 38–40 per cent dry-rubber content and preserved with ammonia. For the most important points, a concentrated latex (creamed latex containing 60 per cent dry-rubber content) was also tested. These two latices were about two years old when the investigation was started, and they gave results which were in good agreement with each other. In the present paper, only the data obtained with the first of the two latices are presented.

scholarly journals STATISTICAL STUDIES ON PROTEIN POLYMORPHISM IN NATURAL POPULATIONS II. GENE DIFFERENTIATION BETWEEN POPULATIONS

Genetics ◽  
1978 ◽  
Vol 88 (2) ◽  
pp. 367-390
Author(s):  
Ranajit Chakraborty ◽  
Paul A Fuerst ◽  
Masatoshi Nei
Keyword(s):  
Genetic Differentiation ◽  
Natural Populations ◽  
Drift Theory ◽  
Alternative Hypotheses ◽  
Mean And Variance ◽  
Statistical Studies ◽  
Different Populations ◽  
Using Data ◽  
Almost All ◽  
Good Agreement

ABSTRACT With the aim of testing the validity of the mutation-drift hypothesis, we examined the pattern of genetic differentiation between populations by using data from Drosophila, fishes, reptiles, and mammals. The observed relationship between genetic identity and correlation of heterozygosities of different populations or species was generally in good agreement with the theoretical expectations from the mutation-drift theory, when the variation in mutation rate among loci was taken into account. In some species of Drosophila, however, the correlation was unduly high. The relationship between the mean and variance of genetic distance was also in good agreement with the theoretical prediction in almost all organisms. We noted that both the distribution of heterozygosity within species and the pattern of genetic differentiation between species can be explained by the same set of genetic parameters in each group of organisms. Alternative hypotheses for explaining these observations are discussed.

scholarly journals Relative validity of a food-frequency questionnaire developed to assess food intake of schoolchildren living in the Brazilian Western Amazon

2011 ◽  
Vol 27 (11) ◽  
pp. 2197-2206 ◽  
Author(s):  
Fernanda Baeza Scagliusi ◽  
Mariana Tarricone Garcia ◽  
Ana Luiza Coutinho Indiani ◽  
Marly Augusto Cardoso
Keyword(s):  
Food Intake ◽  
Food Frequency Questionnaire ◽  
Correlation Coefficients ◽  
Dietary Intakes ◽  
Food Frequency ◽  
Relative Validity ◽  
Vitamins A And C ◽  
The Mean ◽  
Almost All ◽  
Good Agreement

This study aimed to assess the relative validity of a food frequency questionnaire (FFQ) developed to assess food intake of schoolchildren from the Brazilian Western Amazon. The dietary intakes of 61 schoolchildren, aged between six and nine 9 years, were measured using two 24-hour dietary recalls and one FFQ, conducted with the children's, mother or guardians. Validity of the FFQ compared to the mean of the two dietary recalls was assessed using Pearson's correlation coefficient adjusted for attenuation and energy intake, Bland & Altman plots and evaluation of agreement levels between the two assessment methods. Energy-adjusted and deattenuated correlation coefficients ranged from -0.03 for vitamin C, to 0.93 for calcium. The mean coefficient was 0.46. The mean proportion of subjects classified within one quintile by the two methods was 66%. The Bland & Altman plots indicated good agreement for almost all nutrients, with a mean limit of agreement of 108%. These results indicate that, although there was a lack of accuracy for certain nutrients, such as vitamins A and C, the FFQ ensures reliable estimates of intake of most nutrients.

scholarly journals The Physical Properties and Geochemical of Clay from the Bestari Jaya, Kuala Selangor, Selangor, Malaysia for Potential Usage

2020 ◽  
Vol 5 (10) ◽  
pp. 1231-1236
Author(s):  
M. R. Umor ◽  
A. Hussin ◽  
N. Muda
Keyword(s):  
Specific Gravity ◽  
Physical Properties ◽  
Paper Industry ◽  
Xrd Analysis ◽  
Commercial Application ◽  
Average Value ◽  
Plasticity Limit ◽  
Pedestrian Traffic ◽  
L Value ◽  
Almost All

The study emphasis on physical properties and geochemical of the clays from Bestari Jaya area to determine its suitability for any commercial application. Nine samples collected from six boreholes as representative of white and dark clay in the study area. All samples examined through the optical properties test and physical properties such as moisture, specific gravity, Atterberg limit and particle size distributions. The geochemical and mineralogical conducted using XRF and XRD analysis. The clays from Bestari Jaya considered of having variation in the brightness from medium to high brightness as shown by Delta L value (51.32-73.49%). The moisture content ranges between 34.50-81.03%. The plasticity index (PI) and plasticity limit (PL) values found in ranges of 18-32% with an average of 22.22%, and 32-46% with an average of 37.11% respectively. The plasticity limit and index reveals that the Bestari Jaya clays can be classify as kaolinite clays that are suitable for pottery and brick making. The specific gravity ranges between 2.49 – 2.70 with an average of 2.61. The average value is similar to the value of pure china clay (2.6). The SiO2 content in Bestari Jaya clays is between 37.49 – 69.96 wt% and Al2O3 is between 18.92 – 33.02 wt%. While the L.O.I values are between 8.71-16.04%. Kaolinite as the dominant mineral phases in all clay samples with composition ranges from 65-97.7% and an average of 73.12%. Apart of that, quartz in ranges of 5.3 – 20.6%, identified in almost all samples. Muscovite, hematite and magnetite occur as accessory minerals. Referring to standard and result obtained on representative sample, the Bestari Jaya clays potentially used in the production of smaller tiles for unexclusive pedestrian traffic. The presence of significance amount of heavy metals makes it unsuitable to use in the pharmaceutical or paper industry.

A study of the physical properties of SB2s with both the visual and spectroscopic orbits

2020 ◽  
Vol 492 (2) ◽  
pp. 2709-2721
Author(s):  
Luca Piccotti ◽  
José Ángel Docobo ◽  
Roberta Carini ◽  
Vakhtang S Tamazian ◽  
Enzo Brocato ◽  
...  
Keyword(s):  
Stellar Model ◽  
Spectroscopic Binaries ◽  
Adopted Model ◽  
Magnitude Diagram ◽  
Trigonometric Parallaxes ◽  
The One ◽  
The Masses ◽  
Almost All ◽  
Unique Mass ◽  
Good Agreement

ABSTRACT The study of a selected set of 69 double-lined spectroscopic binaries (SB2) with well-defined visual and spectroscopic orbits was carried out. The orbital parallax, the mass, the colour, and the luminosity of each component were derived from observational data for almost all of these systems. We have also obtained an independent estimation of the component masses by comparing the colour–magnitude diagram (CMD) to the stellar evolution tracks reported by Pietrinferni. Nearly all of the observational points on the CMD are located between two tracks of slightly different mass or which fall very close to the one corresponding to a unique mass value. The masses obtained from the stellar model are in good agreement with their empirical values determined by parallax techniques (orbital, Gaia, and dynamical). This means that our adopted model is rather reliable and can therefore be used to infer further information, such as the age of each component in the studied systems. Our results indicate a fair correspondence between the age of primaries and secondary stars within 3σ. Nevertheless, we caution that these age indications suffer of uncertainties due to both inhomogeneities/low precision of the adopted photometric data and possible systematics. Finally, it is statistically shown that along with the orbital and trigonometric parallaxes, the dynamical parallax can serve as a reliable tool for distance estimates.

scholarly journals Counts of Optically Selected Quasars in the Magnitude Range 19

1987 ◽  
Vol 124 ◽  
pp. 657-659
Author(s):  
V. Zitelli ◽  
B. Marano ◽  
G. Zamorani
Keyword(s):  
Current Status ◽  
Variability Analysis ◽  
Magnitude Range ◽  
Adjacent Field ◽  
Almost All ◽  
Good Agreement

We present the current status of a survey of faint, optically selected quasars covering 0.7 square degrees. Candidates have been selected through multicolour search, grism spectroscopy, and, to some extent, variability analysis. Slit spectroscopy for almost all the high priority candidates brighter than J=20.84 yielded 22 confirmed quasars. In the magnitude range J=21–22 our results are in very good agreement with other existing surveys. The extension of the survey on an adjacent field is in progress.

Determination of Proof of Distilled Alcoholic Beverages, Using an Oscillating U-Tube Density Meter

1979 ◽  
Vol 62 (3) ◽  
pp. 653-658 ◽  
Author(s):  
Duane H Strunk ◽  
Jack W Hamman ◽  
Bertha M Timmel
Keyword(s):  
Specific Gravity ◽  
Accurate Method ◽  
Alcoholic Beverages ◽  
Water Solutions ◽  
Tube Density ◽  
Good Agreement

Abstract A simple, rapid, and accurate method is described for determining the concentration of alcohol in ethanol solutions using a density meter. With this instrument, the U-tube is suctionfilled with 0.7 mL sample, and the results are displayed on a digital read-out in specific gravity units. These values are converted by tables to per cent ethanol or proof. For samples under 40° proof, the instrument is standardized on air and water. When testing samples between 40 and 193° proof, the instrument is standardized on air and an ethanol standard having a proof within ±30° of the sample tested. Thus, large corrections for the nonlinearity of the plot of the specific gravity of ethanol vs. proof are avoided. An equation is presented that corrects for this non-linearity, and the result is obtained in per cent ethanol rather than specific gravity. Proof results obtained with this instrument are in good agreement with the values obtained by a pycnometer and/or refractometer for 1–190° proof ethanol-water solutions, vodkas, whiskeys, brandies, and liqueurs.

Loads From Currents and Waves on Net Structures

2012 ◽  
Author(s):  
Are Johan Berstad ◽  
Jørgen Walaunet ◽  
Line Fludal Heimstad
Keyword(s):  
Test Cases ◽  
Fish Farms ◽  
Flow Angle ◽  
Reynolds Number Flow ◽  
Load Calculation ◽  
Aquaculture Industry ◽  
Number Flow ◽  
Net Cages ◽  
Almost All ◽  
Good Agreement

The aquaculture industry has increased rapidly the last 20 years. In almost all fish farms, the fish is held captured in net cages. Net structures are built up with twines as shown in Figure 1. Various parameters of importance for the loads to nets such as solidity, Reynolds number, flow angle relative to mesh and increased flow around twines compared to single twines. This paper outlines such effects. This paper consider loads to net panels considering the net a sum of twines and then sum the forces twine by twine. Based on this approach the paper presents a calculation method for net meshes. The presented load formulation is valid for rectangular and diamond shaped meshes and is valid for any 3D orientation of flow relative to mesh. The presented method for load calculation includes methodology for deriving the forces to a net structure based on knowledge of drag resistance for an individual twine. This methodology is compared with other published formulae and empirical data. A formula is presented based on a twine in wake consideration. The presented formula is compared to measurements for test cases both in terms of a net panel and for a full cage model. Results show good agreement.

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