Liquid junction potentials at mixed electrolyte salt bridges
- Authors: Finkelstein, Noel Phillip
- Date: 1957
- Subjects: Hydrogen-ion concentration -- Measurement , Hydrogen-ion concentration , Electrochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4473 , http://hdl.handle.net/10962/d1011835 , Hydrogen-ion concentration -- Measurement , Hydrogen-ion concentration , Electrochemistry
- Description: The potentiometric method is one of the most exact techniques of electrochemistry. Its use is widespread in both routine measurements, such as pH determination, and in applications which demand the highest accuracy. Perhaps its severest limitation is the error due to liquid junction potentials. Although this has been the subject of much study, and although various means of combating it have been proposed, it has defied all attempts at a satisfactory solution. Indeed, so serious is the position that it has become the accepted practice in the more accurate fields to abandon altogether the use of potentiometric techniques in favour of others, usually less convenient and otherwise less accurate, when the presence of liquid junctions cannot be avoided. Intro. p. 1.
- Full Text:
- Date Issued: 1957
- Authors: Finkelstein, Noel Phillip
- Date: 1957
- Subjects: Hydrogen-ion concentration -- Measurement , Hydrogen-ion concentration , Electrochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4473 , http://hdl.handle.net/10962/d1011835 , Hydrogen-ion concentration -- Measurement , Hydrogen-ion concentration , Electrochemistry
- Description: The potentiometric method is one of the most exact techniques of electrochemistry. Its use is widespread in both routine measurements, such as pH determination, and in applications which demand the highest accuracy. Perhaps its severest limitation is the error due to liquid junction potentials. Although this has been the subject of much study, and although various means of combating it have been proposed, it has defied all attempts at a satisfactory solution. Indeed, so serious is the position that it has become the accepted practice in the more accurate fields to abandon altogether the use of potentiometric techniques in favour of others, usually less convenient and otherwise less accurate, when the presence of liquid junctions cannot be avoided. Intro. p. 1.
- Full Text:
- Date Issued: 1957
Photofluorescence decay times of organic phosphors
- Authors: Hamilton, T D S
- Date: 1957
- Subjects: Fluorescence , Phosphorescence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5525 , http://hdl.handle.net/10962/d1012136 , Fluorescence , Phosphorescence
- Description: The absorption and emission of energy is a fundamental property of any atomic system.When the emission occurs in the visible or near visible region the phenomenon is usually referred to as luminescence or fluorescence. This must be distinguished from thermal radiation as it does not follow Kirchoff's law.
- Full Text:
- Date Issued: 1957
- Authors: Hamilton, T D S
- Date: 1957
- Subjects: Fluorescence , Phosphorescence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5525 , http://hdl.handle.net/10962/d1012136 , Fluorescence , Phosphorescence
- Description: The absorption and emission of energy is a fundamental property of any atomic system.When the emission occurs in the visible or near visible region the phenomenon is usually referred to as luminescence or fluorescence. This must be distinguished from thermal radiation as it does not follow Kirchoff's law.
- Full Text:
- Date Issued: 1957
Some aspects of the animal ecology of Rhenosterbos: Elytropappus rhinocerotis (L.f.) Less
- Authors: Shiff, Clive Julian
- Date: 1957
- Subjects: Animal ecology -- South Africa , Rhenosterbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5880 , http://hdl.handle.net/10962/d1013200
- Description: Rhenosterbos, Elytropappus rhinocerotis (L.f.) Less belongs to a purely South African section ot the Compositae. It is restricted to an area of low rainfall which is evenly distributed over the year. The plant is a specialised xerophyte with minute leaves and white pubescent twiglets. Older stems become woody and dry and bear no leaves. The shrubs have a life span of about eight years; the plants are most succulent and luxurious during the third and fourth year, after which they tend to become woody and scraggly. For this investigation insect material was obtained by sweep-net collection and field observation. In the Grahamatown district 78 collections were made during the period March - November 1953, with data thus obtained being embodied in this work. In addition to this, collections were made in the Cradock-Hofmeyer, Uitenhage, Riversdale, Bot River, Swellendam and Stellenbosch districts. Twenty species of insects have been shown definitely to feed on the plant and there are another 13 which probably feed on it. Of the 20 species attached to the plant, 12 are sucking forms belonging to the Orders Homoptera and Hemipters. They include six Coccids, two Jassids a Cercopid, two Mirids and a Pentstomid. The Coleoptera are represented by one or perhaps two species which feed on the plant. The Lepidoptera are represented by two important species of moth, a Geometrid and a Pyralid. Four species of gall forming Diptera are associated with the plant. There are two species of Trypetidae which are responsible for piriform swellings of growth points and are distributed evenly throughout the bush. There are also two Cecidomyidae one of which develops in the growth points of the shoots and is responsible tor a minute tubular gall. The other develops in a fusiform stem gall. This latter gall has been shown to be more common on smaller bushes than on larger ones, implying that the adult female may show certain selective powers during oviposition. The size of the insect population is held in check by spiders mantids and other general predators. There are several Coccinellids which prey on the scale insects. Rhenosterbos supports a small, well regulated community of insects. The balance between plant and animal is very dellcate because of the high degree of specialisation of the plant. On occasions this balance has been known to break down, and the insects present in abundance have swamped and killed large patches of the plant.
- Full Text:
- Date Issued: 1957
- Authors: Shiff, Clive Julian
- Date: 1957
- Subjects: Animal ecology -- South Africa , Rhenosterbos
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5880 , http://hdl.handle.net/10962/d1013200
- Description: Rhenosterbos, Elytropappus rhinocerotis (L.f.) Less belongs to a purely South African section ot the Compositae. It is restricted to an area of low rainfall which is evenly distributed over the year. The plant is a specialised xerophyte with minute leaves and white pubescent twiglets. Older stems become woody and dry and bear no leaves. The shrubs have a life span of about eight years; the plants are most succulent and luxurious during the third and fourth year, after which they tend to become woody and scraggly. For this investigation insect material was obtained by sweep-net collection and field observation. In the Grahamatown district 78 collections were made during the period March - November 1953, with data thus obtained being embodied in this work. In addition to this, collections were made in the Cradock-Hofmeyer, Uitenhage, Riversdale, Bot River, Swellendam and Stellenbosch districts. Twenty species of insects have been shown definitely to feed on the plant and there are another 13 which probably feed on it. Of the 20 species attached to the plant, 12 are sucking forms belonging to the Orders Homoptera and Hemipters. They include six Coccids, two Jassids a Cercopid, two Mirids and a Pentstomid. The Coleoptera are represented by one or perhaps two species which feed on the plant. The Lepidoptera are represented by two important species of moth, a Geometrid and a Pyralid. Four species of gall forming Diptera are associated with the plant. There are two species of Trypetidae which are responsible for piriform swellings of growth points and are distributed evenly throughout the bush. There are also two Cecidomyidae one of which develops in the growth points of the shoots and is responsible tor a minute tubular gall. The other develops in a fusiform stem gall. This latter gall has been shown to be more common on smaller bushes than on larger ones, implying that the adult female may show certain selective powers during oviposition. The size of the insect population is held in check by spiders mantids and other general predators. There are several Coccinellids which prey on the scale insects. Rhenosterbos supports a small, well regulated community of insects. The balance between plant and animal is very dellcate because of the high degree of specialisation of the plant. On occasions this balance has been known to break down, and the insects present in abundance have swamped and killed large patches of the plant.
- Full Text:
- Date Issued: 1957
Studies on the biology of ants associated with citrus trees
- Authors: Myers, N J
- Date: 1957
- Subjects: Citrus -- Diseases and pests -- Biological control -- South Africa , Ants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5869 , http://hdl.handle.net/10962/d1012923
- Description: Several ant species may be associated with the same honeydew producing insect in citrus orchards. Recently antagonism and competition between two such ants were reported from Letaba. This report stimulated the present study, the purpose of which is to ascertain which ant species are most numerous in citrus orchards ln the Eastern Cape Province; the reasons for these ants being able to occupy orchards; and, finally, their relationships. A survey of the Sundays River Valley and the Fish River Valley revealed that three species - Anoplolepis custodiens Smith, Anoplolepis steingroeveri Forel, and Pheidole megacephala Fabricius - were commonly found in citrus orchards in association with Soft Brown Scale insects. The territorial relationships of these ants were determined by plotting their distribution at intervals for over a year. It was found that this distribution could be correlated with seasonal climatic conditions, the effects of farming practices, brood rearing requirements and behavioural differences between the three species. The ant, A.steingroeveri, had not been previously studied, and since foraging is an integral part of territorial behaviour, some aspects of its biology, and more especially its foraging activity, were investigated to compare it with the known biology of the other two species. Observations on the foraging activity of A. steingroeveri were made at monthly lntervals for almost a year, and correlated with climatic conditions prevailing at the time. Some seasonal and dally variations in foraging behaviour could not be readily explained in terms of the effects of temperature and humidity on the ants. Other factors, includ1ng trophallactic stimulation and overcast skies, were found to influence ant activity. Owing to the apparent lack of information in the literature and possibility of periodic honeydew production by Soft Brown Scale insects controlling ant activity was investigated in the laboratory. The results of this study showed that it was not likely that honeydew excretion restricted the activity of the ants. Several investigators have also found that many interrelated climatic factors correlated with ant foraging behaviour, but have expressed dissatisfaction at not being able to reach the crux of the matter. To clarify the issue a constant temperature chamber was constructed in which a colony of Crematogaster ants was housed and the ants were subjected to a series of temperatures at different humidities, all other factors were eliminated or kept constant. The effects of these two factors on the thermokinetics and foraging activity of the ants were registered. This thesis contains several sections and at the end of each the results are discussed in the light of the available literature and comparisons are drawn between the species under investigation. The main results are given in the summary. After the summary two appendices are included. One is an attempt to compare the effect on ant size of the honeydew diet of orchard colonies with the proteinaceoue diet of veld ants. The other appendix is an experiment to control citrus ants with an insecticide.
- Full Text:
- Date Issued: 1957
- Authors: Myers, N J
- Date: 1957
- Subjects: Citrus -- Diseases and pests -- Biological control -- South Africa , Ants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5869 , http://hdl.handle.net/10962/d1012923
- Description: Several ant species may be associated with the same honeydew producing insect in citrus orchards. Recently antagonism and competition between two such ants were reported from Letaba. This report stimulated the present study, the purpose of which is to ascertain which ant species are most numerous in citrus orchards ln the Eastern Cape Province; the reasons for these ants being able to occupy orchards; and, finally, their relationships. A survey of the Sundays River Valley and the Fish River Valley revealed that three species - Anoplolepis custodiens Smith, Anoplolepis steingroeveri Forel, and Pheidole megacephala Fabricius - were commonly found in citrus orchards in association with Soft Brown Scale insects. The territorial relationships of these ants were determined by plotting their distribution at intervals for over a year. It was found that this distribution could be correlated with seasonal climatic conditions, the effects of farming practices, brood rearing requirements and behavioural differences between the three species. The ant, A.steingroeveri, had not been previously studied, and since foraging is an integral part of territorial behaviour, some aspects of its biology, and more especially its foraging activity, were investigated to compare it with the known biology of the other two species. Observations on the foraging activity of A. steingroeveri were made at monthly lntervals for almost a year, and correlated with climatic conditions prevailing at the time. Some seasonal and dally variations in foraging behaviour could not be readily explained in terms of the effects of temperature and humidity on the ants. Other factors, includ1ng trophallactic stimulation and overcast skies, were found to influence ant activity. Owing to the apparent lack of information in the literature and possibility of periodic honeydew production by Soft Brown Scale insects controlling ant activity was investigated in the laboratory. The results of this study showed that it was not likely that honeydew excretion restricted the activity of the ants. Several investigators have also found that many interrelated climatic factors correlated with ant foraging behaviour, but have expressed dissatisfaction at not being able to reach the crux of the matter. To clarify the issue a constant temperature chamber was constructed in which a colony of Crematogaster ants was housed and the ants were subjected to a series of temperatures at different humidities, all other factors were eliminated or kept constant. The effects of these two factors on the thermokinetics and foraging activity of the ants were registered. This thesis contains several sections and at the end of each the results are discussed in the light of the available literature and comparisons are drawn between the species under investigation. The main results are given in the summary. After the summary two appendices are included. One is an attempt to compare the effect on ant size of the honeydew diet of orchard colonies with the proteinaceoue diet of veld ants. The other appendix is an experiment to control citrus ants with an insecticide.
- Full Text:
- Date Issued: 1957
The morphology of the Weberian apparatus of Labeo umbratus Smith
- Authors: Dennis, Clive Roy
- Date: 1957
- Subjects: Fishes -- Anatomy -- South Africa , Weberian apparatus -- Morphology , Fishes -- South Africa -- Tyumie River , Eastern Cape (South Africa) -- Fishes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5907 , http://hdl.handle.net/10962/d1014766
- Description: In Labeo umbratus only the first three anterior vertebrae undergo any modification. These vertebrae are not completely anchylosed with each other and are closely associated with the four Weberian ossicles. Movement is however restricted between these vertebrae since this is essential for the efficient functioning of the Weberian ossicles. The first vertebra is well developed the absence of a spinous process and neural arch in the first vertebra may perhaps be explained by the findings of some workers who derive the claustrum from the former and the scaphium from the latter. A small muscle has its origin on the claustrum and its insertion in the angle formed by the dorsal and medial processes of the scaphium. A second muscle originates in the pit-like excavation of the first vertebra and is inserted on the ventral process of the scaphium. The intercalarium possesses horizontal, articular and ascending processes; a portion of the horizontal process being imbedded in the interossicular ligament. In Labeo umbratus it is unlikely that the intercalarium represents (if it does so at all) the entire neural arch of the second vertebra. From a morphological point of view it seems likely that the intercalarium may function as a lever. A transversely situated ductus endolymphaticus joins the two sacculi to each other. The sagitta, in the region of the ductus endolymphaticus has a long, lateral "wing-like" process which projects into the cavity of the sacculus. The sacculus anilagena are innervated by the n. saccularis and the n. lagenaris respectively. The ductus endolymphaticus is prolonged posteriorly into a median unpaired sinus endolymphaticus. Although the only serious objection to Weber's theory is the fact that there could be no differential action of the two ears, the basic idea seems valid. Sagemehl's theory cannot be accepted. It seems likely that the Weberian ossicles are necessary structures for audition and to the hydrostatia function of the air-bladder.
- Full Text:
- Date Issued: 1957
- Authors: Dennis, Clive Roy
- Date: 1957
- Subjects: Fishes -- Anatomy -- South Africa , Weberian apparatus -- Morphology , Fishes -- South Africa -- Tyumie River , Eastern Cape (South Africa) -- Fishes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5907 , http://hdl.handle.net/10962/d1014766
- Description: In Labeo umbratus only the first three anterior vertebrae undergo any modification. These vertebrae are not completely anchylosed with each other and are closely associated with the four Weberian ossicles. Movement is however restricted between these vertebrae since this is essential for the efficient functioning of the Weberian ossicles. The first vertebra is well developed the absence of a spinous process and neural arch in the first vertebra may perhaps be explained by the findings of some workers who derive the claustrum from the former and the scaphium from the latter. A small muscle has its origin on the claustrum and its insertion in the angle formed by the dorsal and medial processes of the scaphium. A second muscle originates in the pit-like excavation of the first vertebra and is inserted on the ventral process of the scaphium. The intercalarium possesses horizontal, articular and ascending processes; a portion of the horizontal process being imbedded in the interossicular ligament. In Labeo umbratus it is unlikely that the intercalarium represents (if it does so at all) the entire neural arch of the second vertebra. From a morphological point of view it seems likely that the intercalarium may function as a lever. A transversely situated ductus endolymphaticus joins the two sacculi to each other. The sagitta, in the region of the ductus endolymphaticus has a long, lateral "wing-like" process which projects into the cavity of the sacculus. The sacculus anilagena are innervated by the n. saccularis and the n. lagenaris respectively. The ductus endolymphaticus is prolonged posteriorly into a median unpaired sinus endolymphaticus. Although the only serious objection to Weber's theory is the fact that there could be no differential action of the two ears, the basic idea seems valid. Sagemehl's theory cannot be accepted. It seems likely that the Weberian ossicles are necessary structures for audition and to the hydrostatia function of the air-bladder.
- Full Text:
- Date Issued: 1957
The solubility of barium sulphate in water at 25°
- Authors: Rosseinsky, D R
- Date: 1957
- Subjects: Chemistry, Physical and theoretical , Solubility , Barium sulfate
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4491 , http://hdl.handle.net/10962/d1013097
- Description: Barium sulphate is a widely used analytical precipitate and for this reason its properties have been extensively studied. The variety of results encountered with barium sulphate samples prepared by different methods is an indication of the complex nature of this interesting substance. Intro., p. 8.
- Full Text:
- Date Issued: 1957
- Authors: Rosseinsky, D R
- Date: 1957
- Subjects: Chemistry, Physical and theoretical , Solubility , Barium sulfate
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4491 , http://hdl.handle.net/10962/d1013097
- Description: Barium sulphate is a widely used analytical precipitate and for this reason its properties have been extensively studied. The variety of results encountered with barium sulphate samples prepared by different methods is an indication of the complex nature of this interesting substance. Intro., p. 8.
- Full Text:
- Date Issued: 1957
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