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(1952). Use of Thoriated Tungsten Electrodes in Inert Gas Shielded Arc Welding—Investigation of Potential Hazard. American Industrial Hygiene Association Quarterly: Vol. 13, No. 4, pp. 191-195.

Investigations of the effect of high pressures of Na (100 to 130 atmospheres) and of Ar (60 to 80 atmospheres) showed that these gases are effective in reversing the phases of an oil in water emulsion. Nitrous oxide did not cause reversal at pressures as high as 53 atmospheres nor did helium as high as 107 atmospheres. We found CO2 most effective in reversing the emulsions and attributed this to its chemical properties. It is suggested that these observations may help to explain the narcotic effects of inert gases.

Measurements have been made of the separation produced by thermal diffusion in all the binary mixtures of the inert gases (except Kr-X and Rn mixtures) at temperatures ranging from -180 to 400° C. The temperature dependence of the thermal diffusion ratio, k T , and of R T ( R T = k T /[ k T (∞)] 1 , where [ k T (∞)] 1 is the theoretical value for molecules behaving like rigid elastic spheres) has been deduced. The results indicate that, in general, R T increases with the temperature in the lower range and becomes constant at high temperatures. The constant value is first attained at a temperature which varies from mixture to mixture, but its magnitude is nearly the same for all mixtures. It corresponds with a repulsive force index of 11, if the molecules are treated as centres of repulsive force only. The results have been compared with those calculated by R. Clark Jones (1940, 1941) for a gas mixture in which the two molecular species have identical force fields of the Lennard-Jones type, with repulsive force index v = 9 and attractive force index v' = 5. The theoretical results give R T as a function of T / T c , where T c is the critical temperature of the gas. This relation with the critical temperature is supported by the experimental results, though there are difficulties in the comparison due to the non-identical nature of the force fields in the experimental mixtures. It appears, however, that the observed behaviour could be explained by a Lennard-Jones model if the force indices were suitably chosen, and that a study of the temperature dependence of R T in isotopic mixtures would enable the indices to be determined with some precision.

A resistance-capacity analogue machine for the study of the saturation and desaturation of tissues with oxygen and inert gases is described. Two types of deviation from saturation time courses of exponential form are found, and the occurrence of these depends upon the blood flow rate in relation to the geometrical arrangement of capillaries in the tissue. The difference between the effects of parallel and antiparallel blood flow in adjacent capillaries upon the saturation time course is shown. The relevance of the results to the estimation of regional blood flow in tissues from saturation time courses is discussed.

Inert-gas Arc Welding of Aluminium Aluminium is used widely in metal fabrication processes, chiefly on account of its lightness, the ease with which it may be cast, and its extreme ductility. It is also highly resistant to corrosion, owing to the formation of a protective film of oxide on the surface of the metal. This latter property, however, becomes a disadvantage when it is desired to weld the metal, as the oxide film hinders consoli dation of the metal on fusion, and even when broken down it re-forms almost instantaneously in air. Aluminium may be welded by either gas or arc processes, but arc welding is more satisfactory as the area over which the heat is generated is smaller and the speed of welding can thus be increased. The thermal conductivity of aluminium is high, being five times greater than that of steel, and hence with arc welding distortion and any tendency to crack are shield, usually of argon or helium. This gas shield allows the arc to disperse the oxide film, and by the exclusion of oxygen prevents it from being reformed. Th use of these welding methods gives greater freed m in design, and the welding torch may even be used to form a weld inside a partly sealed con tainer. As these welding methods are capable of automatic operation higher welding speeds may be achieved, and this feature, together with the use of highe w lding currents than are employed in manual welding, enables welding to be carried out on thicke metal than would otherwise be the case. Two main types of inert-gas shielded welding are used, and are shown diagrammatically in Figs, la and lb. The inert-gas tungsten-arc method (Fig. la) uses a non-consumable tungsten electrode for producing the arc, and the welding is normally carried out by the use of a filler rod of aluminium. reduced. With both gas and arc welding the oxide may be dispersed by means of fluxes, but the disadvantage of this procedure is that the flux residues are corrosive, and after completion of the weld thorough cleaning of the metal is essential. Joints have thus to be so designed as to avoid trapping flux. These problems have led to the development of forms of arc welding which utilize an inert-gas arc

SUMMARY A method is described which permits continuous determination of oxygen consumption during anaesthesia in the presence of inert gases. Owing to the diffusion characteristics of an inert gas as nitrous oxide, there are two conditions which must be fulfilled in order to measure the oxygen uptake:— 1 A constant volume in the ventilatory system, which includes the patient's lungs, the anaesthesia machine and the measuring device. 2 Constant partial pressures of gases in the system. These conditions are fulfilled when the Engstrom respirator in a closed system is connected to a volume-controlling device which automatically adjusts the flow of metabolic oxygen into the system in such a way that the volume is kept constant. The oxygen is delivered from a hydrostatic spirometer of new design which permits a direct linear relationship between the change in hydrostatic pressure of the spirometer and the volume of delivered oxygen at atmospheric pressure. The oxygen is fed into the respirator system through a special slide valve, controlled by the changes in volume, and with a reciprocal action which keeps the volume constant. Constancy of partial pressures is maintained by adding the inert gas (nitrous oxide) through a precision rotameter into the system. Due to the reciprocal action of the oxygen slide valve a constant volume is ensured. A Beckman oxygen analyser is used as a zero instrument for the control of partial pressures. Model experiments with an artificial lung and a constant artificial oxygen consumption and gas mixtures of different composition have shown that the method has an error of 1.1 per cent. (S.D. ± 11.4 ml at a mean oxygen output from the spirometer of 1008 ml). Experiments on dogs with determination of the oxygen consumption by the method of Krogh utilising oxygen alone, and the method described in this paper when nitrous oxide was present, showed close agreement between the values for determined oxygen, which were all within the margins of error. Determinations during anaesthesia and surgical procedures have shown that the method is simple and permits accurate continuous monitoring of the oxygen uptake during various conditions. ZUSAMMENFASSUNG Es wird eine Methode beschrieben, die eine kontinuierliche Bestimmung des Sauerstoffverbrauches in Gegenwart inaktiver Gase wahrend der Narkose gestattet. Infolge der Diffusionsbesonderheiten eines inaktiven Gases wie Stickoxydul, mussen zwei Bedingungen bei der Messung des Sauerstoffverbrauches erfullt werden: 1 Ein konstantes Volumen im Ventilationssystem, das die Lunge des Patienten, den Narkoseapparat und das Messgerat umfasst. 2 Ein konstanter Partialdruck der Gase im System. Diese Bedingungen werden erfullt, wenn der als geschlossenes System verwendete Engstromrespirator mit einer Volumenkontrollvorrichtung verbunden wird, die den Ersatz des im Stoffwechsel verbrauchten Sauerstoffes automatisch so regelt, dass das Volumen im System konstant gehalten wird. Der Sauerstoff wird von einem hydrostatischen Spirometer neuer Konstruktion geliefert, bei dem ein direktes lineares Verhaltnis zwischen der Anderung des hydrostatischen Druckes im Spirometer und dem Volumen des gelieferten Sauerstoffes bei atmospharischem Druck besteht. Der Sauerstoff wird dem Respiratorsystem uber ein besonderes Schieberventil zugefuhrt, das durch Volumsanderungen betatigt wird und so durch den gegensinnigen Ventilmechanismus das Volumen konstant halt. Der Partialdruck im System wird durch Zusetzen des inaktiven Gases (Stickoxydul) mit Hilfe eines Prazisionsrotameters konstant gehalten. Ein Beckman'scher Sauerstoffanalysator dient als Eichinstrument zur Kontrolle der Partialdrucke. Modellversuche mit einer kunstlichen Lunge bei Verwendung von Gasgemischen verschiedener Zusammensetzung und einem konstanten kunstlichen Sauerstoffverbrauch zeigten, dass die Methode eine Fehlerbreite von 1,1% hat. (Mittlere Abweichung: ± 11,4 ml. bei einem durchschnittlichen Sauerstoffzufluss aus dem Spirometer von 1008 ml.) Die Bestimmung des Sauerstoffverbrauches an Hunden mit der Krogh'schen Methode (mit Sauerstoff allein) und mit der in dieser Arbeit beschriebener Methode (Sauerstoff in Gegenwart von Stickoxydul) ergab weitgehend ubereinstimmende Werte, die alle innerhalb der Fehlerbreite lagen. Bestimmungen wahrend Narkose und Operationen zeigten, dass die Methode einfach ist und eine genaue kontinuierliche Messung des Sauerstoffverbrauches unter verschiedenartigen Bedingungen erlaubt.

When an inert gas of moderate or high solubility in blood is inhaled, the rate at which the alveolar concentration rises toward the inspired concentration increases as the inspired concentration is increased. The only previous systematic analysis of whole-body uptake of inert gases to allow for this effect was restricted to a single, artificial, respiratory pattern and the numerical calculations had to be made on a digital computer. This paper develops the theory for a range of respiratory patterns and shows how the computations may be made on a slightly modified form of a simple electric analogue. It is shown that the rate of saturation of the body increases less markedly with inspired concentration if the inspired alveolar ventilation, rather than the expired alveolar ventilation, is kept constant during the saturation process. Conversely, washout is more rapid with a constant inspired ventilation than with a constant expired ventilation. The theory is extended to show how the uptake of one inert gas may substantially affect the uptake of another, administered simultaneously. uptake, distribution and elimination; induction; recovery; drugs; inhaled anesthetics; nitrous oxide; diethyl ether; halothane; computers; ventilation; concentration effect; alveolar ventilation Submitted on February 13, 1964

The apparatus described is a small-scale sealed ecological system capable of confining the rare gases without significant loss. Biological test chambers suitable for a variety of biological specimens are illustrated. A “canned” pump provides gas circulation; a K2CO3 scrubber column removes CO2. Metabolized oxygen is replenished automatically from an O2 cylinder which is controlled by an ultrasensitive pressure switch. Provision is made for recording oxygen uptake. The equipment provides a constant temperature within 0.5 C over the range of 5–50 C and is capable of maintaining uninterrupted operation for periods of up to 14 days. small scale sealed ecological system; biological test chambers Submitted on February 4, 1963