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 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.

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 Rubber in Latex

1935 ◽  
Vol 8 (3) ◽  
pp. 443-447
Author(s):  
Ode Vries
Keyword(s):  
Specific Gravity ◽  
Practical Interest ◽  
Trade Association ◽  
Complicated Problem ◽  
Experimental Errors ◽  
The Difference

Abstract In a study on the specific gravity of preserved latex, Rhodes comes to the conclusion that the specific gravity of rubber in latex may be estimated at 0.902, and that the figure of 0.914, found by us several years ago, and the figure of 0.912 used as a basis for the tables in the contracts of the Rubber Trade Association of London, are high. Rhodes's figure is based on a large experimental material (852 samples of preserved latex from nine different estates), and agrees well with the estimated figure of 0.901, to which Scholtz and Klotz came from 85 observations on fresh later in Malaya. Our figure was based on a large number of observations on normal estate latex, as well as on latex from specially tapped groups of trees; the difference between 0.902 and 0.914 is too large to be ascribed to experimental errors, though these of necessity are rather high, as the specific gravity of rubber can only be calculated by extrapolation over a zone much greater than the experimental zone itself. It seems of sufficient interest to subject these deviating results to a closer study, as this may, perhaps, throw some further light on a rather complicated problem which is not without practical interest.

The Specific Gravity of Rubber in Hevea Latex

1940 ◽  
Vol 13 (1) ◽  
pp. 130-132
Author(s):  
O. de Vries
Keyword(s):  
Specific Gravity ◽  
Reasonable Agreement ◽  
Serum Proteins ◽  
Interesting Problem ◽  
Prolonged Action ◽  
Rubber Content ◽  
Rubber Particles ◽  
Average Figure ◽  
Acid Coagulation ◽  
Corrected Figure

Abstract Since my former communication on this subject several papers have appeared which form valuable contributions to the interesting problem of the actual specific gravity of the rubber particles in (original or preserved) Hevea latex. Rhodes recalculated his data, and came to an average figure of 0.9064 for the specific gravity of rubber in ammoniated latex, preserved during several weeks in the East; the rubber content being determined after coagulation by acetic acid in the usual way. Using the term proposed in my former paper, this may be called the specific gravity of “crepe rubber in preserved latex”, which may differ from that of “crepe rubber in original latex” by the effect of possible changes by the prolonged action of ammonia, by the settling out of the sludge (ammonium magnesium phosphate, mixed with protein-like substances), and other changes that occur in preserved latex. Leaving these unknown factors out of consideration, we have to take into account the fact that the rubber content was determined by acid coagulation, which means that a certain amount of serum substances, principally proteins, was precipitated with the rubber, and may have influenced its specific gravity. In my former communication I have shown that the specific gravity of “crepe rubber in latex” is found lower, the higher the rubber content of the original latex, i.e., the smaller the ratio of serum to rubber, and the smaller, therefore, the amount of acid-precipitated serum proteins in per cent of the rubber. Plotting, in this line of thought, Rhodes' figure in the graph (Figure 1), it will be seen that it corresponds to 45 grams rubber per 100 cc, or about 46.6 in percentage of weight, not abnormal for a preserved latex. Protein, precipitated with the rubber, has a still smaller effect in another figure given by Rhodes, namely, the specific gravity of rubber from a centrifuged cream of 56.7 per cent rubber content (acid coagulation). The corrected figure for the specific gravity of this rubber is given by Rhodes as 0.9011, which in Figure 1 corresponds to 55.5 grams of rubber per 100 cc, or about 58.5 per cent by weight; this is in reasonable agreement with the real figure of 56.7, taking into account the unavoidable errors of an extrapolation, such as in Figure 1.

Valence electron spectroscopy of inhomogeneous media

1992 ◽  
Vol 50 (2) ◽  
pp. 1150-1151
Author(s):  
A. Howie ◽  
D.W. McComb
Keyword(s):  
Specific Gravity ◽  
Loss Function ◽  
Electron Spectroscopy ◽  
Valence Electron ◽  
Peak Height ◽  
Loss Functions ◽  
Loss Peak ◽  
High Energies ◽  
Valence Electron Density ◽  
Electron Microscopist

The bulk loss function Im(-l/ε (ω)), a well established tool for the interpretation of valence loss spectra, is being progressively adapted to the wide variety of inhomogeneous samples of interest to the electron microscopist. Proportionality between n, the local valence electron density, and ε-1 (Sellmeyer's equation) has sometimes been assumed but may not be valid even in homogeneous samples. Figs. 1 and 2 show the experimentally measured bulk loss functions for three pure silicates of different specific gravity ρ - quartz (ρ = 2.66), coesite (ρ = 2.93) and a zeolite (ρ = 1.79). Clearly, despite the substantial differences in density, the shift of the prominent loss peak is very small and far less than that predicted by scaling e for quartz with Sellmeyer's equation or even the somewhat smaller shift given by the Clausius-Mossotti (CM) relation which assumes proportionality between n (or ρ in this case) and (ε - 1)/(ε + 2). Both theories overestimate the rise in the peak height for coesite and underestimate the increase at high energies.

Float for Specific Gravity Determinations

1895 ◽  
Vol 39 (1011supp) ◽  
pp. 16162-16162
Author(s):  
T. Lohnstein
Keyword(s):  
Specific Gravity
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