The Properties of Rubber Prepared from Dialyzed Latex

1939 ◽  
Vol 12 (4) ◽  
pp. 695-705
Author(s):  
H. P. Stevens ◽  
J. W. Rowe

Abstract Rubber articles are prepared from ammonia-preserved latex by two principal processes, viz., evaporation or coagulation, or by a combination of both. The object of this work was to determine what advantages are to be obtained by the use of a latex purified by dialysis. An 8-gallon batch of normal ammoniapreserved latex (from Hevea brasiliensis) was available and all the rubbers were prepared from this batch unless otherwise stated. The latex was kept for several days and decanted from the sludge which settles out. After straining, it was stored in one-gallon cans until required for use. Some of the latex was dialyzed through membranes of regenerated cellulose in the apparatus previously described by the authors. Some aqueous ammonia was added to the latex daily to preserve stability, and three charges of distilled water were used to complete the purification. A pressure was applied to the latex and adjusted to allow slight dilution so that there was no formation of paste on the membranes. The latex was analyzed, before and after dialysis, for total solids and dry rubber content. The former were determined by evaporating a weighed portion of the latex to constant weight at 70°. The dry rubber content was determined by coagulating the latex with about an equal volume of 1% acetic acid, crepeing the coagulum on a washing machine, and drying the crepe at, 70°

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1176
Author(s):  
Hanna Dorna ◽  
Agnieszka Rosińska ◽  
Dorota Szopińska

Alternaria dauci (J.G. Kühn) J.W. Groves et Skolko and A. radicina Meier, Drechsler et E.D. Eddy are important seed-transmitted pathogens of carrot. The aim of this study was to evaluate the effects of acetic acid treatments on the quality of stored carrot seeds. Seeds of two samples were soaked for 30 min in 0.5, 1 and 2% acetic acid. Controls included untreated seeds, seeds soaked in distilled water and seeds treated with fungicide Zaprawa Nasienna T 75 WS/DS (a.i. thiram 75%). Germination, vigour and health of untreated and treated seeds were evaluated before and after 5 and 12 months of storage at 4 and 20 °C. Seeds of both samples treated with 0.5 and 1% acetic acid were characterized by higher germination capacity after storage than untreated seeds. However, treatments with 1 and 2% acetic acid negatively affected seed vigour. Generally, seeds of both samples treated with acetic acid were characterized by lower infestation with A. alternata and A. radicina after storage than untreated seeds and seeds soaked in distilled water. Moreover, acetic acid often controlled these fungi more effectively than the fungicide. Regardless of the storage duration, infestation with fungi was higher if seeds of both samples were stored at a lower temperature.


Author(s):  
M. M. Jibrin ◽  
A. D. Mohammed

The study was design to evaluate the smoke repellency effect of prepared neem leaves, against mosquito. The dried neem powder was used for making the insecticide, 10 g of powdered leaves sample was weight into a 200 ml beaker, and 5.0 g of starch was weight and added to the leave sample in the beaker. The mixture was stirred and 5.0 ml of distilled water was added gradually to the mixture in little quantity while stirring. The beaker with wet insecticide mixture was dried in an oven until a constant weight was obtained. The prepared neem insecticide was distributed among the households to use at night, to substitute synthetic insecticides. The users were randomly selected within the study area. The data was collected based on the time of application, number of bites receive before and after the application this was done based on 0-5 rating scale. The result revealed that the prepared insecticide is 100% effective though the effectiveness is dependent to time taken after application. The questionnaire was also used to assess the view of the users on the adverse effect they experienced upon the exposure to neem tree leaves prepared sample. The study has been concluded that neem leaves smoke is effective in repelling mosquito, and it can be an alternative to the synthetic insecticides hence it is safe for the users and the environment.


1946 ◽  
Vol 19 (1) ◽  
pp. 176-186
Author(s):  
J. H. E. Hessels

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.


2013 ◽  
Vol 35 (1) ◽  
pp. 87-99 ◽  
Author(s):  
Grzegorz Nowak ◽  
Henryk Panak

The forms of occurence of potassium and sodium were studied in the grasses <i>Dactylis glomerata</i> L., <i>Poa annua</i> L., <i>Festuca rubra</i> L. and dendelion (<i>Taraxacum officinale</i> Web.) treated with increasing mineral fertilizer doses, magnesium and microelements, under conditions of pot culture. The plants took up potassium in amounts greatly exceeding their requirement, and sodium in very small amounts. Mineral NPK doses increased in the tested plants both the content of potassium and sodium forms soluble in trichloroacetic and acetic acids and water. Magnesium and microelements had no major influence on the content of these potassium forms, but they increased the concentration of analogous forms of sodium in <i>Taraxacum officinale</i> and did not influence their accumulation in the grasses. Potassium and sodium compounds were completely extracted from the plants with trichloroacetic, whereas acetic acid extracted 88-95 percent of potassium and 66-74 percent of sodium. Distilled water extracted 70-77 and 28-33 percent of potassium and sodium, respectively.


Author(s):  
O. Shkromada ◽  
Yu. Dudchenko ◽  
T. Necherya ◽  
I. Abubakari Kavla

In this field, complex disinfectants were contrasted using effective concentrations against bacteria and spore-forming microorganisms. A significant problem for the owners is the emergence of resistance of strains of microorganisms in the existing production and the same disinfectants. Investigation of trusted working concentrations of disinfectants that do not have a corrosive effect on metal structures. According to the results of research and production, contrast is an effective disinfectant for reducing E. coli and S aureus at 0,3 – 0,5% concentration at exposure for 30 min. and consumption of 100 - 400 cm3 / m2. Laboratory researches were carried out in laboratories of microbiological faculties of veterinary medicine of Sumy National Agrarian University. Disappearance gaps and disinfection on the market in Kyiv. Samples were drawn in the refrigerators from the walls, ceilings and floors. Refrigerated chambers made of stainless steel are made up of rubber and plastic elements. Metals are very vulnerable to corrosion with more concentrated acids and alkali. This was taken into account when choosing a disinfectant and its effective organizations. As a disinfectant used the drug contrast (manufacturer PE "Kronos Agro", Ukraine). The disinfectant was taken at a dose of 100 ml per 1 m2. To produce the culture was prepared basic products containing 1000 mg of the drug in 1 ml of distilled water. The experimental solutions were prepared for study with the main formulations developed. Representatives had extraordinary effects. The  disks were leaked through the disinfectant to obtain a zone of retention of high bacteria and fungi. The reliability of disinfectant destroying the micro-organisms of E. coli and S. aureus test cultures was also known. For the trusted production preparations, the contrast at the trusted enterprises was carried out by the rehabilitation of the premises of the educational laboratory of the Sumy National Agrarian University (premises for animals, dairies, refrigeration chambers). Renovation and test activities were performed at 0,1, 0,25 and 0,5 % of exposed contrast with exposure for 60, 30 and 10 min. the disinfectant was consumed 250 cm3 / m2. Upon completion of the studies, the investigated tests were investigated with distilled water (flow rate - 1000 cm3 / m2). Water that has been washed away test products, presented in specially prepared capabilities. Test results for this after disinfection were also investigated with distilled water, which was found on the disinfectant. To study the corrosion activity of the disinfectant used metal plates 1h1sm2. The metal samples were welded to the fifth mark after the commission before and after the study. 0,5; 1,0; 1,5; 2,5 % contrast solutions were used in the study. For comparison, in the experiments used 2% of productive. M. bovis mycobacterial cultures were grown on Pavlovsky's glycerol medium. The bacterial culture was transferred into sterile vials and sterile isotonic material containing 0,05 cm3 / mg was added. A large amount of delay zone in Petri dishes containing 0,5 % of S. aureus disinfectant, 3,5 times S. cholerase 1,8 S. Enteritidis 2 more than 0,5% formal form . Higher indicators of bacterial properties of the disinfectant contrast at a concentration of 0,5%.


2018 ◽  
Vol 97 (12) ◽  
pp. 1339-1345 ◽  
Author(s):  
T. Jiang ◽  
Y.R. Guo ◽  
X.W. Feng ◽  
Y. Sa ◽  
X. Yang ◽  
...  

Recent studies suggested that bleaching agents may whiten teeth by oxidizing the fluorescent materials, which are the proteins located in the organic-inorganic interface. Therefore, we postulated that fluorescence of dentin came from dentin phosphoprotein (DPP) and that bleaching agents might bleach dentin by oxidizing DPP. Fifty-six specimens were randomly divided into 4 groups and exposed to distilled water, hydrogen peroxide (HP), ethylenediamine tetraacetic acid disodium salt (EDTA), and acetic acid for 24 h. After measuring the organic and inorganic components, fluorescence, and color characteristics of dentin before and after exposure, we found that when DPP was removed from dentin by EDTA, fluorescent intensity declined proportionally with the reduction in Raman relative intensity, and dentin was whitened considerably, with an Δ E value 6 times higher than that of the distilled water group. On the contrary, due to the incapability of acetic acid to dissolve DPP during decalcification, fluorescent intensity values and tooth color remained nearly unchanged after exposure to acetic acid. Dentin exposed to neutral HP showed no obvious morphologic and organic/inorganic component changes except for the destruction of DPP. Similarly, dramatically decreased fluorescent intensity and lightened color were found in the HP group. Moreover, DPP solution of the HP group exhibited decreased ultraviolet absorbance, especially between 250 and 300 nm, which arose from aromatic amino acids. The results indicated that DPP was responsible for the fluorescent properties of dentin and that HP might bleach dentin by the oxidization of aromatic amino acids in DPP. These findings are of great significance in promoting our further understanding of the mechanism of tooth bleaching and the fluorescent property of normal dentin.


1990 ◽  
Vol 78 (1) ◽  
pp. 101-104 ◽  
Author(s):  
Joe Collier ◽  
Patrick Vallance

1. The dose-response to acetylcholine has been examined in dorsal hand veins of healthy volunteers before and after removal of the endothelium. 2. Measurements were made in single dorsal hand veins during local infusions of acetylcholine. The vein was irrigated with distilled water to remove the endothelium. Dilator studies were performed in vessels preconstricted by a continuous infusion of noradrenaline. 3. In the endothelium-intact vessel the dose-response to acetylcholine was biphasic; low doses produced venodilatation with higher doses causing venoconstriction. 4. Dilatation to low doses of acetylcholine was abolished by prior irrigation with distilled water, consistent with denudation of the endothelium by this process. Irrigation augmented the constriction seen in response to higher doses of acetylcholine. 5. This is the first demonstration of an endothelium-dependent biphasic dose-response to acetylcholine in man. The results raise questions as to the possible physiological actions of endogenous acetylcholine and as to the use of the acetylcholine dose-response curve as a marker of endothelial function.


2011 ◽  
Vol 71 (3) ◽  
pp. 693-699 ◽  
Author(s):  
JM. Galo ◽  
DP. Streit-Junior ◽  
RN. Sirol ◽  
RP. Ribeiro ◽  
M. Digmayer ◽  
...  

The objective of this research was to verify the presence of spermatic abnormalities on semen of Brycon orbignyanus after cryopreservation. Semen was collected from ten four-year-old males who presented secondary reproductive characteristics for migrating fish. Sperm was evaluated for motility, vigor and spermatic morphology before and after cryopreservation. A cryoprotectant solution was made of 20 mL of yolk egg, 5.0 g of glucose and dimethyl sulfoxide diluted in distilled water (10 mL: 90 mL). The diluted semen (1:3, semen:solution) was submitted to nitrogen steam for 24 hours and then to liquid nitrogen (-196 ºC) for 60 days. Cryopreservation decreased the percentage of normal spermatozoa from 62.20% to 54.60%. Consequently, the percentage of spermatozoa with secondary abnormalities increased from 8.50% to 15.00%. However, there was no difference in primary abnormalities. Both spermatic motility and vigor were decreased in cryopreserved semen compared with fresh semen. In conclusion, cryopreservation of semen of B. orbignyanus increased the percentage of secondary abnormalities and decreased the spermatic motility and vigor.


2017 ◽  
Vol 888 ◽  
pp. 184-187
Author(s):  
Salwa Ismail ◽  
Mohammad Faizal Mohd Razali ◽  
Izwan Johari ◽  
Zainal Arifin Ahmad ◽  
Shah Rizal Kasim

In this study, the geopolymer mortars were synthesized with fly ash (FA) and silica powder as aluminosilicate sources and a combination of sodium hydroxide (NaOH) solution, sodium silicate (Na2SiO3) solution and distilled water as alkaline activator. Commercial sago was used as a pore former in the mortars. The percentage of sago used were 10, 20 and 30 wt% of FA. The amount of added water used in each mixture was 5% by weight of FA, NaOH solution and Na2SiO3 solution. The formed geopolymer mortars were cured for 1, 3 and 7 days and sintered at 1000 °C. X-ray fluoresence (XRF) shown that FA contains higher amount of silica (SiO2) and alumina (Al2O3) which is important as aluminosilicate sources. The properties of the geopolymer mortars before and after sintered at 1000 °C have been investigated. The results show that geopolymer mortars with 10% of sago content with curing time of 7 days and sintered at 1000 °C give the highest compressive strength of 13.5 MPa.


2012 ◽  
Vol 454 ◽  
pp. 26-29
Author(s):  
Hui Dong Su ◽  
Zhong Hua Shi

Titanium oxide coatings (Ti/TiO2)were formed on the titanium net surface by micro-arc oxidation(MAO) in Na3PO4 solution using an AC power supply. Then the titanium oxide coatings were treated by acetic acid or La(NO3)3 aqueous solution to improve its activity. The structures and photocatalytic ability of titanium oxide coatings before and after surface treatment were characterized and evaluated by XRD, SEM, EDX. It was found that the titanium oxide film is mainly made of titanium and anatase .When acetic acid aqueous concentration is 0.1mol•L-1 and soak time is 6 hour ,the Ti/TiO2 films photocatalytic degradation rate increased from 15% to 33.6%. When La(NO3)3 aqueous concentration is 0.1mol•L-1 and soak time is 12 hour, the Ti/TiO2 films photocatalytic degradation rate increased from 15% to 34.8%.


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