H.—34.

The experiments undertaken by the Department in co-operation with the Laboratory with a view to determining the effect of storage on swelling properties of various coals were completed. It had been suggested that the swelling might be reduced after exposure to the air, thus rendering the coal more suitable for use in continuous vertical gas retorts. From this point of view the results were disappointing, as very little if any alteration in the swelling properties of the coals tested was detected after eight months' exposure to the weather. During the year consideration has been given to the possible exploitation of cinnabar and asbestos, but so far no actual experiments have been made. Progress in coal research and utilization abroad is being closely followed, and during his recent visit to Great Britain Mr. W. A. Joiner, the Fuel Chemist of the Laboratory, had the opportunity of spending a month at H.M. Fuel Research Station, and of visiting the new coal-hydrogenation plant erected by Imperial Chemical Industries, Ltd., at Billingham, this company's coal-testing laboratories at Winnington, the Safety in Mines Research Stations at Buxton and Sheffield, and other places of interest in connection with the utilization of coal. In this way it has been possible to make direct contact with those engaged in fuel investigational work in Great Britain, and to gain some first-hand knowledge of the advances being made. It has recently been proposed that a physical and chemical survey of the, coal resources of the Dominion should be commenced, and the matter is under discussion at the present time. Government Stokes. As in previous years, numerous samples were analysed in connection with the purchase of stores by the Stores Control, Post Office, and other Government Departments. These included concrete, cleaning-compounds, cancelling-inks, calico, fencing-wire, fuel oil, formalin, galvanized iron, motorspirit, red lead, rope, soldering-mixtures, shellac, sulphuric acid, transformer oils, type-metal, and switchboard materials. Several interesting cases of corrosion were dealt with during the year. In an investigation, lasting some months, into a particularly severe type of corrosion of lead cable-sheathing, the corrosive nature of the impregnated jute wrapping was strikingly demonstrated. A comparative examination was made of a series of tent-canvasses to ascertain the nature of the various waterproofing and anti-mildew treatments which they had received. The suitability of each for the collection of rain-water for drinking purposes was also examined. One sample (ironchromium process), being free from any water - extractable constituent of a toxic nature, was recommended as the best for this purpose. The facilities available at the Laboratory for the testing of paints and painters' materials are being made use of to an increasing extent by the various Government Departments. Owing to the many new products that have become available, the possibility arises not only of gross adulteration of paints, but also of inferior results being obtained through the mixing of incompatible materials. In this, as in other fields, the excellent technical and reference library that has been built up over a period of years is proving invaluable. Gas-inspection. The gas-supplies of the four main centres and of the other principal towns were examined regularly for calorific value, purity, and pressure. With one exception, they were all of satisfactory quality throughout the year. Research. Pozzolanic Material. —During the year a further series of samples of volcanic material collected by the Geological Survey was examined for pozzolanic activity. The work is being continued. Mineral Waters, Rotorua-Taupo District. —The analytical examination of these waters was completed during the year, and tne results will be incorporated in a bulletin to be issued by the Director, Geological Survey. Spray Research. —Work for the Plant Research Station, Palmerston North, included many analyses of apples and apple-leaves for arsenic residue from trees which were sprayed under varying conditions of pressure and of fineness of the spray-mist. Several samples of lead arsenate were examined during the year. In one case a sample which had been supplied as lead arsenate and had caused severe damage to fruit-trees proved on analysis to be arsenious oxide (white arsenic). Further samples of tobacco grown for the purpose of studying the effect of cultural practices on the nicotine content were examined. The results will be published at an early date in the Journal of Science and Technology. The highest percentage of nicotine found in the leaf was 15-9, calculated on the dry weight. With a view to checking the ravages of white butterfly, cabbages were sprayed with lead arsenate. It then became necessary to investigate the amount of spray residue. With whole cabbages the amounts of arsenic found were as high as 0-2 gr. arsenious oxide per pound, but when the outside leaves were removed the amounts became almost negligible, being of the order of 0-0003 gr. per pound. Coal. —Large-scale storage experiments extending over a period of eight months were carried out with bituminous coal from various collieries in order to ascertain the effect of storage on the coking properties of the coals. It was hoped that the excessive swelling which characterizes some of the coals would be reduced by oxidation consequent on open storage, and that the range of usefulness of the coals would be increased, particularly for gas-making in vertical retorts. The results, however, disclosed very little difference in the coking-qualities of the coals after storage for eight months.

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