A study of the host plants of the tobacco flea beetle was made in Pittsylvania County from April 1 to September 23, 1939. The work was divided into field observations, rearing experiments end population studies. From field observations made throughout the season it was found that this insect fed mostly on the solanaceous plants. especially tobacco. In the spring before the tobacco was transplanted and in the late summer after the harvesting of the crop, the flea beetle fed on a wide variety or plants. Rearing experiments were made using 29 plant species representing 11 families most of which were known as hosts of the adult beetle. These were planted in a small plot of land of a common tobacco soi1. Beetles were caged over these for 4 days and records were kept as to the number of adults that developed from the eggs laid. No beetles emerged from any of the non-solanaceous plants, whereas at least a few developed on all the Solanaceae tested. Many more beetles developed on tobacco, potato and jimson weed than on any of the others. For the population studies tobacco flea beetle and solanaoeous weed counts were made in 14 tobacco fields selected for this purpose. Beetle counts were made at weekly intervals from May 26 until the middle of August and were computed to show the average number of beetles per tobacco plant. Weed counts were made in June and September and were computed to show the average number of weeds per 100 square yards. The data indicated that only tobacco in the beds and potato in the field were of importance in building up the early flee beetle infestation of tobacco. / Master of Science

From observations of the field and laboratory operations, several ideas as to improvement of the construction and operation of the pasteurizer were conceived. / Master of Science

1. A two prism spectrograph has been designed and oonstruoted with which it is believed Raman spectra may be obtained. 2. Attempts have been made using the spectrograph to obtain Raman spectra. These attempts, are as yet unsuccessful. / M.S.

We may summarize the purposes of this investigation as follows: A report on this investigation was made to Dr. John H. Yoe of the University of Virginia in order to see what reactions he considered to be of analytical significance and should be further investigated. He considers only three to be of any practical importance. They are as follows: 1. 7A-Oleic Acid. Solubility of the alkaline earth salts of some higher fatty acids. 2. 69A- 2-Acetamino 6-Aminobenzo Thiazole. A colorimetric reagent for iridium. 3. 71A 2-Hydroxy 3-Nitro 5-Sulfobenzoic Acid. A colorimetric reagent for ferric iron. A further investigation of compound 71A, as a colorimetric reagent for ferric iron, reveals that the sensitivity of this reaction is not great enough for it to be of any practical importance, since we have reagents (2) for this ion that are several times more sensitive. Prospective reagent No. 69A for iridium is being further investigated by Mr. J. R. Noell (1). A report on 7A will be taken up in Part II of this thesis. 1. It has been shown that there is very little difference in the solubility of the same alkaline earth salt of stearic, oleic, linoleic, and linolenic acids in the solvents, water, benzene, absolute ethyl alcohol and ether. 2. It has been shown that there is very little difference in the solubility of the different alkaline earth salt of stearic, oleic, linoleic, and linolenic acids in the solvents, water, benzene, absolute ethyl alcohol and ether, and benzene. 3. The solubility of the alkaline earth salt of these acids increases slightly with unsaturation, but does not increase as the degree of unsaturation increases. / M.S.

It is quite common practice in automotive and aircraft engine maintenance, operation, and research to employ any one of several types of instruments now on the market for determining the air-fuel ratio by exhaust gas analysis. It was the purpose of this investigation to determine the most important operating characteristics, especially range and accuracy, of each of these types of instruments. The theory underlying the operation of this kind of apparatus was studied critically, and certain tests were performed on representative makes in order to observe the operation of each type under service conditions. These tests consisted essentially of connecting the analyzers to the exhaust pipe of a single-cylinder engine and comparing the analyazer readings with the true air-fuel ratio determined by accurately measuring the air and fuel supplied to the engine while the instruments were being observed. This procedure was repeated for a number of different carburetor settings, all other factors being kept as nearly constant as possible during a given series of runs. The effect of variations in engine spark advance and the pressure of the gas supplied to the instruments was also investigated. The test revealed several interesting facts. Study of the operating principles of the several instruments indicated that they were limited te air fue1 ratios below about 14 to 1, and this has been conclusively proved by these experiments. This limitation applies to thermal conductivity, hot-wire catalytic, and relative density types. W While the most expensive makes of instruments were not tested, it was found that, in general, the limit of accuracy is not greater than one-half of one air-fue1 ratio, regardless of the operating principle employed. Large variations in the pressure and rate of flow of the exhaust supplied to the analyzers were found to cause considerable deviations in those instruments which did not employ some kind of device to insure a steady and uniform supply. Certain features of design and construction which effect the reliability of the various types of exhaust gas analyzers are also reviewed in this thesis, and some of the more important chemical methods of analysis are treated briefly. / Master of Science

The appearance of synthetic fertilizers on the market has increased the interest in the so-called "minor elements". Much work with water and sand cultures has proven the necessity of these elements for successful plant growth. However, the need for these elements in crop production on field soils has not been studied intensively, nor have we sufficient knowledge as to the effect of our changing fertilizer practices on the necessity for minor elements. A number of field studies to determine the necessity of boron, manganese, zinc, copper and ether minor elements, when applied singly or in combinations of two or more, have given phenomenal increases in yields under certain plant and soil conditions. Under other conditions there has been no response from their use when applied to the soil either singly or in combinations of two or more elements. It is the purpose of this study to determine under what soil conditions the need of minor elements becomes a part of our soil management problem and what part natural Chilean nitrate of soda plays in preventing and correcting this condition. Also this investigation was developed to give a comparison of yield and growth of various crops grown intensively on a number of soil types where fertilized with purified carriers of nitrogen, phosphorus and potassium and where these elements were supplied from commonly used commercial carriers. Another purpose of this study was to determine how long these soils could be cropped before minor elements would become a limiting factor in crop production as shown by yields and deficiency symptoms. / Master of Science

This study is concerned with the resistance of tobacco seedlings to a second attack of downy mildew caused by Peronospora tabacina Adam. Observations were made on the development and duration of resistance following recovery of tobacco seedlings from downy mildew. The duration of the period of resistance is variable and the observations indicate that plants in the greenhouse recovering during the summer remain resistant longer than do plants recovering from an initial attack during the winter. Samples of leaf tissue from recovered (resistant), infected and previously uninfected (susceptible) plants grown in soil in the greenhouse were analyzed for ammonia-nitrogen, nitrate-nitrogen, reducing sugars and total sugars. Similar analyses were made of samples of leaf tissue from tobacco plants grown in crocks of quartz sand and irrigated with nutrient solutions and from plants grown in crocks of sand-peat mixture to which various mixed fertilizers were added. There was no correlation between the ammonia-nitrogen content of tobacco plants, as determined in these experiments, and the response of the tobacco plant and its susceptibility to attack by P. tabacina, but there was a strong indication that such a relationship exists. Recovered plants contained a higher ratio of total sugar to nitrate-nitrogen than did comparable plants which had never been infected. Furthermore the ratio of total sugar to nitrate-nitrogen was lower in plants infected for a second time than it was in plants from the same lot shortly after they had recovered from the initial attack. It seems probable however that the changes in the nitrate-nitrogen and sugar content in recovered tobacco leaves are an indication of recovery and are not responsible for the resistance possessed by such plants. A series of experiments were performed to test the immediate effect of several nutrient salts and of sugar upon the sporulation of the fungus on the leaves of diseased tobacco plants. There was a very definite response in sporulation to some of these treatments, especially to potassium nitrate, calcium nitrate, and sucrose, but it is not known whether the response of sporulation of the fungus to such treatment is related to the type of resistance possessed by recovered plants. Sodium chloride and calcium chloride were dissolved in water and applied to the soil in which young tobacco plants were growing in the greenhouse. Although increased chloride in one of the sand cultural experiments seemed to protect the plants somewhat against downy mildew, application of solutions of these salts to the soil at the rates used (100 lbs. And 138 lbs. Per acre respectively) produced no noticeable effect on the severity of the disease or subsequent recovery of the plants. The leaves of recovered (resistant) tobacco plants are usually reduced in number, the lower ones having been killed by the initial attack of the fungus. Removal of the leaves from healthy tobacco plants in imitation of this condition did not produce resistance to an attack by P. tabacina. The artificial production of necrotic areas on healthy tobacco leaves in simulation of those usually following sporulation of P. tabacina on diseased leaves had no effect either on the susceptibility of the plants to infection or upon sporulation of the fungus on leaves already infected at the time the necrotic areas were induced. Results of attempts to confer immunity from downy mildew upon an entire plant by infection of a single leaf of the plant were inconclusive, since under the conditions of the experiment it was impossible to be sure that the single leaf was infected. However, the indication is that infection of a single leaf will not render the entire plant immune from a second attack by the fungus. / Master of Science

Master of Science

Master of Science

Tall oil is a mixture of rosin acids, fatty acids, and non-acids resulting from acidification of the soaps separating out from the kraft pulp process evaporator liquor. The present uses of tall oil center chiefly around its fatty acid content, but are limited for some purposes because of the rosin content. Separation of these constituents makes each available as such. The rosin, as crystalline abietic acid, has specific possibilities as a raw material. Rosin and fatty acids are separated chiefly by distillation, although chemical means and extraction have been proposed to overcome such objections as corrosion and losses as pitch, incurred in distillation. Chlorination is used as a step in the purification of tall oil, or to produce a sticky chlorinated oil, but no separation based on the use of chlorine appears to have been proposed. It was proposed in this investigation to chlorinate the fatty acid double bonds in hopes that the properties of this product would be such as to permit of a separation. The effects of solvent, light, heat, and catalysts were studied to determine the optimum conditions for such a reaction, and the effect of chlorination upon the rosin and fatty acids, respectively, under specific conditions was determined, It was found that the use of CCl₄ solvent and ultraviolet light accelerate chlorine consumption and promote the addition of chlorine, but do not entirely stifle the substitution reaction. Rosin and fatty acid double bonds are attacked to about an equal extent under these conditions. The chlorinated oil is entirely soluble in most common solvents at room temperature. Petroleum ether insolubles increase slightly over the amount obtained from untreated oil. It is recommended that the range of chlorination conditions be extended to a more complete study of possible results, and that other chemical attacks be investigated. / Master of Science