A preliminary investigation of the toxic principle of Moraea polystachya Ker
- Dry, L J
- Authors: Dry, L J
- Date: 1954
- Subjects: Iridaceae Moraea polystachya ker
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4461 , http://hdl.handle.net/10962/d1011494
- Description: A member of the Iridaceae family, the plant (also known as the Blue Tulp) ... is a monocotyledon. The blue tulp grows profusely in rainy parts of the Union, for example along much of the Cape coastal belt as far east as Grahamstown, in both the Karroos, and in parts of the Transvaal. It is a perennial plant but only appears above the ground once a year for about two months. This is at the start of the rainy season and in Grahamstown the plant appears in April and May, after which it disappears again. Chapter 1, p.1.
- Full Text:
- Date Issued: 1954
- Authors: Dry, L J
- Date: 1954
- Subjects: Iridaceae Moraea polystachya ker
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4461 , http://hdl.handle.net/10962/d1011494
- Description: A member of the Iridaceae family, the plant (also known as the Blue Tulp) ... is a monocotyledon. The blue tulp grows profusely in rainy parts of the Union, for example along much of the Cape coastal belt as far east as Grahamstown, in both the Karroos, and in parts of the Transvaal. It is a perennial plant but only appears above the ground once a year for about two months. This is at the start of the rainy season and in Grahamstown the plant appears in April and May, after which it disappears again. Chapter 1, p.1.
- Full Text:
- Date Issued: 1954
An investigation of the equivalent circuit of a conductivity cell
- Authors: Allison, Francis Sutton
- Date: 1954
- Subjects: Electrolytic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4508 , http://hdl.handle.net/10962/d1013376
- Description: ( i) A linear circuit is shown not to explain the behaviour of a conductivity cell towards a long rectangular pulse of amplitude less than the decomposition potential of the solution in the cell. (ii) It is shown that the flow of current through the cell is governed by diffusion to the electrode. The diffusion current expression is the familiar one used in the case of diffusion up to a plane micro-electrode, except that in this case the concentration in the layer next to the electrode is not zero, but only somewhat less than the bulk concentration. (iii) Except during a short initial period (less than 10 seconds), the resistance of the electrolytic cell varies directly with the square root of the time for which an e.m.f. (less than the decomposition potential) is applied to the cell, and inversely with the concentration difference between the electrode surface and the bulk of the solution.
- Full Text:
- Date Issued: 1954
- Authors: Allison, Francis Sutton
- Date: 1954
- Subjects: Electrolytic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4508 , http://hdl.handle.net/10962/d1013376
- Description: ( i) A linear circuit is shown not to explain the behaviour of a conductivity cell towards a long rectangular pulse of amplitude less than the decomposition potential of the solution in the cell. (ii) It is shown that the flow of current through the cell is governed by diffusion to the electrode. The diffusion current expression is the familiar one used in the case of diffusion up to a plane micro-electrode, except that in this case the concentration in the layer next to the electrode is not zero, but only somewhat less than the bulk concentration. (iii) Except during a short initial period (less than 10 seconds), the resistance of the electrolytic cell varies directly with the square root of the time for which an e.m.f. (less than the decomposition potential) is applied to the cell, and inversely with the concentration difference between the electrode surface and the bulk of the solution.
- Full Text:
- Date Issued: 1954
Aspects of the resorcinol-formaldehyde condensation
- Waldron, Ronald Augustus Frank
- Authors: Waldron, Ronald Augustus Frank
- Date: 1954
- Subjects: Resorcinol , Formaldehyde
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4514 , http://hdl.handle.net/10962/d1013460
- Description: An attempt was made to producea -β or Ϫ - resorcinyl alcohol from disubstituted resorcinyls. To accomplish this 3,5-dibromo-β-resorcylic acid was reacted with lithium aluminium hybride, a mild reducing agent, in an attempt to reduce the acid group to the alcohol group. This disubstituted resorcinol was recovered unchanged. 3,5-dibromo-β-resorcyl-aldehyde was reduced by lithium aluminium hydride, but, instead of the alcohol forming, resinification took place. 2-methyl- 4-ethylresorcinol and 4,6-diethyrecorinol were reacted with formaldehyde under alkaline and acidic conditions. In each case a resin formed. The above experlments indicated that condensation took place in the meta position of the resorcinol molecule. Trimethylresorcinol was therefore reacted with formaldehyde under alkaline conditions, resulting in a small quantity ot the alcohol derivative. A better yield of the alcohol derivative was obtained by the hydrolysis or the chloromathyl derivative. In pursuing this line, a seres of new compounds and their derivatives were prepared. The condensation of the alcohol derivative with trimethylresorcinol and also with resorcinol was investigated.
- Full Text:
- Date Issued: 1954
- Authors: Waldron, Ronald Augustus Frank
- Date: 1954
- Subjects: Resorcinol , Formaldehyde
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4514 , http://hdl.handle.net/10962/d1013460
- Description: An attempt was made to producea -β or Ϫ - resorcinyl alcohol from disubstituted resorcinyls. To accomplish this 3,5-dibromo-β-resorcylic acid was reacted with lithium aluminium hybride, a mild reducing agent, in an attempt to reduce the acid group to the alcohol group. This disubstituted resorcinol was recovered unchanged. 3,5-dibromo-β-resorcyl-aldehyde was reduced by lithium aluminium hydride, but, instead of the alcohol forming, resinification took place. 2-methyl- 4-ethylresorcinol and 4,6-diethyrecorinol were reacted with formaldehyde under alkaline and acidic conditions. In each case a resin formed. The above experlments indicated that condensation took place in the meta position of the resorcinol molecule. Trimethylresorcinol was therefore reacted with formaldehyde under alkaline conditions, resulting in a small quantity ot the alcohol derivative. A better yield of the alcohol derivative was obtained by the hydrolysis or the chloromathyl derivative. In pursuing this line, a seres of new compounds and their derivatives were prepared. The condensation of the alcohol derivative with trimethylresorcinol and also with resorcinol was investigated.
- Full Text:
- Date Issued: 1954
Some aspects of the insect ecology of citrus orchards
- Authors: Smithers, Courtenay Neville
- Date: 1954
- Subjects: Citrus -- Diseases and pests , Insect pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5883 , http://hdl.handle.net/10962/d1013231
- Description: After a brief introduction, the species of Citrus on which the investigations were carried out are mentioned. This is followed by an account of the methods of collection used, and a discussion of their relative merits. The main method used was that in which the trees were fumigated with hydrocyanic acid gas, and the insects falling from the trees were taken up on sheets. The location of the areas where collections were made are then given. An annotated list of the species taken by the fumigation method follows, and the numerical data obtained at the same time regarding the species present is given in an abbreviated form and discussed. A more detailed discussion of the relative abundance of the species is then undertaken. The discussion of the ecology of the insects commences with the insects listed according to their activities, so far as known, and an account of five trees of striking faunal differences is given. A broader discussion of citrus ecology is then given, based on the data previously presented; this ends with a short reminder of the inherent 'oneness' of the insect with its environment.
- Full Text:
- Date Issued: 1954
- Authors: Smithers, Courtenay Neville
- Date: 1954
- Subjects: Citrus -- Diseases and pests , Insect pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5883 , http://hdl.handle.net/10962/d1013231
- Description: After a brief introduction, the species of Citrus on which the investigations were carried out are mentioned. This is followed by an account of the methods of collection used, and a discussion of their relative merits. The main method used was that in which the trees were fumigated with hydrocyanic acid gas, and the insects falling from the trees were taken up on sheets. The location of the areas where collections were made are then given. An annotated list of the species taken by the fumigation method follows, and the numerical data obtained at the same time regarding the species present is given in an abbreviated form and discussed. A more detailed discussion of the relative abundance of the species is then undertaken. The discussion of the ecology of the insects commences with the insects listed according to their activities, so far as known, and an account of five trees of striking faunal differences is given. A broader discussion of citrus ecology is then given, based on the data previously presented; this ends with a short reminder of the inherent 'oneness' of the insect with its environment.
- Full Text:
- Date Issued: 1954
Studies on the behaviour of Anomala opacicollis (Pér)
- Authors: Miles, Peter Wallace
- Date: 1954
- Subjects: Anomala -- Behavior -- Zimbabwe , Anomala -- Control -- Zimbabwe , Anomala -- Larvae -- Zimbabwe , Scarabaeidae -- Zimbabwe , Beetles -- Control -- Zimbabwe , Tobacco -- Diseases and pests -- Zimbabwe , Tobacco industry -- Zimbabwe , Insecticides -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5901 , http://hdl.handle.net/10962/d1013514
- Description: [Summary]: The larvae of Anomala opacicollis (Pér), of Melolonthid and of other Rutelid species, attack tobacco in Southern Rhodesia, and are more commonly called "whitegrubs". Whitegrubs are widespread in the sandveld areas where tobacco is grown and, at the Trelawney Station of the Tobacco Research Board of Southern Rhodesia, where this work was done, A. opacicollis was the predominant species. An account o£ the one year life cycle is given. The adults eat the leaves of various indigenous trees and an account of an experiment on the food preferences of A. opacicollis adults is given, and the main food sources in the Trelawney area are listed. An experiment is described which shows that the beetles prefer to lay their eggs in the veld or in manured broken land rather than in normal ploughed lands. The larvae are erratically distributed in lands and experiments on larval movement suggest that this is mainly due to concentration of the larvae at discrete concentrations of organic matter in the soil. The temperature and moisture condition of the top 3" of soil are found to be those which attact the larvae. It is suggested that tho larvae prefer and move to soil which contains the lowest amount of moisture which keeps the soil air spaces saturated. lt appears that the preferred temperature decreases with increasing soil moisture content and it is suggested that this is due to the respiratory requirements of the larvae. Soil pH, compaction and fertiliser content and the presence of plants do not appear to influence larval movements. A theory is developed concerning the mechanism of movements in the soil and it is suggested that, in the absence of a continuous gradient, the speed but not the direction of movement is influenced by conditions to which the larvae are sensitive. Evidence in support of thie theory is given. Studies on the survival of larvae at different soil moisture contents and temperatures show that conditions in the top 3" of soil are not likely to be lethal in spite of the high temperatures and low moisture contents found there. The relation of whitegrub behaviour to agricultural problems is discussed. Other workers published evidence indicating that early ploughed lands were attractive to whitegrubs; this is shown not to be the case and the previous evidence is re-interpreted. Such lands tend to contain concentrations of whitegrubs round the borders. The reason for this is discussed and it is suggested that lands should be ploughed early to confine whitegrub infestations in this manner. Soils low in fertility through repeated cultivation are commonly believed to contain more whitegrubs than virgin soil. However, behaviour studies suggest that it is the activity and not the size of the population which is affected by soil fertility. The time at which tobacco is planted is known to determine the extent of subsequent whitegrub damage. The reason for this is to be found in the life cycle of whitegrubs and the results of an experiment on time of planting in relation to whitegrub damage are given. Some insecticides are shown to be more repellant than others to A. opacicollis larvae and the influence of this fact on the assessment of soil insecticide effectiveness in the field is discussed. Reference is made to a method developed by the writer for the determination of insecticide effectiveness under the conditions of erratic whitegrub distribution which normally occur.
- Full Text:
- Date Issued: 1954
- Authors: Miles, Peter Wallace
- Date: 1954
- Subjects: Anomala -- Behavior -- Zimbabwe , Anomala -- Control -- Zimbabwe , Anomala -- Larvae -- Zimbabwe , Scarabaeidae -- Zimbabwe , Beetles -- Control -- Zimbabwe , Tobacco -- Diseases and pests -- Zimbabwe , Tobacco industry -- Zimbabwe , Insecticides -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5901 , http://hdl.handle.net/10962/d1013514
- Description: [Summary]: The larvae of Anomala opacicollis (Pér), of Melolonthid and of other Rutelid species, attack tobacco in Southern Rhodesia, and are more commonly called "whitegrubs". Whitegrubs are widespread in the sandveld areas where tobacco is grown and, at the Trelawney Station of the Tobacco Research Board of Southern Rhodesia, where this work was done, A. opacicollis was the predominant species. An account o£ the one year life cycle is given. The adults eat the leaves of various indigenous trees and an account of an experiment on the food preferences of A. opacicollis adults is given, and the main food sources in the Trelawney area are listed. An experiment is described which shows that the beetles prefer to lay their eggs in the veld or in manured broken land rather than in normal ploughed lands. The larvae are erratically distributed in lands and experiments on larval movement suggest that this is mainly due to concentration of the larvae at discrete concentrations of organic matter in the soil. The temperature and moisture condition of the top 3" of soil are found to be those which attact the larvae. It is suggested that tho larvae prefer and move to soil which contains the lowest amount of moisture which keeps the soil air spaces saturated. lt appears that the preferred temperature decreases with increasing soil moisture content and it is suggested that this is due to the respiratory requirements of the larvae. Soil pH, compaction and fertiliser content and the presence of plants do not appear to influence larval movements. A theory is developed concerning the mechanism of movements in the soil and it is suggested that, in the absence of a continuous gradient, the speed but not the direction of movement is influenced by conditions to which the larvae are sensitive. Evidence in support of thie theory is given. Studies on the survival of larvae at different soil moisture contents and temperatures show that conditions in the top 3" of soil are not likely to be lethal in spite of the high temperatures and low moisture contents found there. The relation of whitegrub behaviour to agricultural problems is discussed. Other workers published evidence indicating that early ploughed lands were attractive to whitegrubs; this is shown not to be the case and the previous evidence is re-interpreted. Such lands tend to contain concentrations of whitegrubs round the borders. The reason for this is discussed and it is suggested that lands should be ploughed early to confine whitegrub infestations in this manner. Soils low in fertility through repeated cultivation are commonly believed to contain more whitegrubs than virgin soil. However, behaviour studies suggest that it is the activity and not the size of the population which is affected by soil fertility. The time at which tobacco is planted is known to determine the extent of subsequent whitegrub damage. The reason for this is to be found in the life cycle of whitegrubs and the results of an experiment on time of planting in relation to whitegrub damage are given. Some insecticides are shown to be more repellant than others to A. opacicollis larvae and the influence of this fact on the assessment of soil insecticide effectiveness in the field is discussed. Reference is made to a method developed by the writer for the determination of insecticide effectiveness under the conditions of erratic whitegrub distribution which normally occur.
- Full Text:
- Date Issued: 1954
The determination of the solubility of mercurous chloride at 25°C
- Authors: Dry, Mark Eberhard
- Date: 1954
- Subjects: Mercuric chloride
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4463 , http://hdl.handle.net/10962/d1011576 , Mercuric chloride
- Description: After the publication of the paper by Gledhill and Malan in which precision conductance techniques were used for the first time in the determination of the solubility of silver chloride, Dr. N.H. Perton of Christchurch College, New Zealand, wrote to Gledhill and suggested that the same methods might be rewarding if applied to the determination of the solubility of mercurous chloride. A review of the Chemical literature showed that the values for the solubility of mercurous chloride were not at all consistent. Into., p. 1
- Full Text:
- Date Issued: 1954
- Authors: Dry, Mark Eberhard
- Date: 1954
- Subjects: Mercuric chloride
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4463 , http://hdl.handle.net/10962/d1011576 , Mercuric chloride
- Description: After the publication of the paper by Gledhill and Malan in which precision conductance techniques were used for the first time in the determination of the solubility of silver chloride, Dr. N.H. Perton of Christchurch College, New Zealand, wrote to Gledhill and suggested that the same methods might be rewarding if applied to the determination of the solubility of mercurous chloride. A review of the Chemical literature showed that the values for the solubility of mercurous chloride were not at all consistent. Into., p. 1
- Full Text:
- Date Issued: 1954
The polarographic determination of trace elements in blister and refined copper
- Authors: Eve, Adrian John
- Date: 1954
- Subjects: Copper , Polarographs , Polarography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4467 , http://hdl.handle.net/10962/d1011769 , Copper , Polarographs , Polarography
- Description: In the complete analysis of copper the following impurities are generally determined: silver, gold, lead, arsenic, antimony, selenium, tellurium, iron, zinc, cobalt, nickel, oxygen, sulphur, and, less commonly, tin and phosphorus. The actual copper content varies around 99.0% in blister copper; in the refined metal the content is somewhat higher, usually over 99.9%. The concentrations of the individual impurities vary from tenths to thousandths of one per cent.
- Full Text:
- Date Issued: 1954
- Authors: Eve, Adrian John
- Date: 1954
- Subjects: Copper , Polarographs , Polarography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4467 , http://hdl.handle.net/10962/d1011769 , Copper , Polarographs , Polarography
- Description: In the complete analysis of copper the following impurities are generally determined: silver, gold, lead, arsenic, antimony, selenium, tellurium, iron, zinc, cobalt, nickel, oxygen, sulphur, and, less commonly, tin and phosphorus. The actual copper content varies around 99.0% in blister copper; in the refined metal the content is somewhat higher, usually over 99.9%. The concentrations of the individual impurities vary from tenths to thousandths of one per cent.
- Full Text:
- Date Issued: 1954
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