Venice fares better during the crisis than other states The voyages of the galere d a mercato The principal trade routes to and from Antwerp French merchants registered as living in Antwerp1 5 8 5 1 56 Surplus capital in Genoa between 1 5 10 and The Netherlands under Burgundian rule in 1 1 79 The urban population increase - 3 The United Provinces and Spain Calculating the accounts of the V. Venice in the seventeenth century 23 The defeat of the Spanish Armada 33 Roundships in Venice 37 A 'raw barbarian' 41 A western merchant watches the production of eastern 43 spIces Allegory of the trade of Danzig 49 The official pomp of the Venetian state 52 The surrender of Breda, 59 Domestic slavery in Brazil 64 69 Nymphenburg in 1 Wealth in the sixteenth century:
F, Air or oxygen expansion valve. G, Vacuum vessel with liquid air or oxygen. H, Carbon dioxide and air outlet. O, Carbon dioxide coil. To gain that end, the idea naturally occurred of using adiabatic expansion, not intermittently, as when gas is allowed to expand suddenly from a high compression, but in a continuous process, and an obvious way of attempting to carry out this condition was to enclose the orifice at which expansion takes place in a tube, so as to obtain a constant stream of cooled gas passing over it.
But further consideration of this plan showed that although the gas jet would be cooled near the point of expansion owing to the conversion of a portion of its sensible heat into dynamical energy of the moving gas, yet the heat it thus lost would be restored to it almost immediately by the destruction of this mechanical energy through friction and its consequent reconversion into heat.
Thus the net result would be nil so far as change of temperature through the performance of external work was concerned.
But the conditions in such an arrangement resemble that in the experiments of Thomson and Joule on the thermal changes which occur in a gas when it is forced under pressure through a porous plug or narrow orifice, and those experimenters found, as the former of them had predicted, that a change of temperature does take place, owing to internal work being done by the attraction of the gas molecules.
To Linde belongs the credit of having first seen the essential importance of this effect in connexion with the liquefaction of gases by adiabatic expansion, and he was, further, the first to construct an industrial plant for the production of liquid air based on the application of this principle.
The change of temperature due to the Thomson-Joule effect varies in amount with different gases, or rather with the temperature at which the operation is conducted. At ordinary temperatures oxygen and carbonic acid are cooled, while hydrogen is slightly heated.
But hydrogen also is cooled if before being passed through the nozzle or plug it is brought into a thermal condition comparable to that of other gases at ordinary temperatures—that is to say, when it is initially cooled to a temperature having the same ratio to its critical point as their temperatures have to their critical points—and similarly the more condensible gases would be heated, and not cooled, by passing through a nozzle or plug if they were employed at a temperature sufficiently above their critical points.
Each gas has therefore a point of inversion of the Thomson-Joule effect, and this temperature is, according to the theory of van der Waals, about 6. Olszewski has determined the inversion-point in the case of hydrogen, and finds it to be But the decrement of temperature is proportional to the difference of pressure and inversely as the absolute temperature, so that the Thomson-Joule effect increases rapidly by the combined use of a lower temperature and greater difference of gas pressure.
Siemens indeveloped and extended by Ernest Solvay inand subsequently utilized by numerous experimenters in the construction of low temperature apparatus, a practicable liquid air plant was constructed by Linde. The gas which has passed the orifice and is therefore cooled is made to flow backwards round the tube that leads to the nozzle; hence that portion of the gas that is just about to pass through the nozzle has some of its heat abstracted, and in consequence on expansion is cooled to a lower temperature than the first portion.
In its turn it cools a third portion in the same way, and so the reduction of temperature goes on progressively until ultimately a portion of the gas is liquefied.
Apparatus based on this principle has been employed not only by Linde in Germany, but also by Tripler in America and by Hampson and Dewar in England.
The last-named experimenter exhibited in December a laboratory machine of this kind fig. The initial cooling is not necessary, but it has the advantage of reducing the time required for the operation.
The efficiency of the Linde process is small, but it is easily conducted and only requires plenty of cheap power. When we can work turbines or other engines at low temperatures, so as to effect cooling through the performance of external work, then the economy in the production of liquid air and hydrogen will be greatly increased.
A, Cylinder containing compressed hydrogen. B and C, Vacuum vessels containing carbonic acid under exhaustion and liquid air respectively. D, Regenerating coil in vacuum vessel. This treatment was next extended to hydrogen. Dewar showed in that hydrogen cooled in this way and expanded in a regenerative coil from a pressure of atmospheres was rapidly reduced in temperature to such an extent that after the apparatus had been working a few minutes the issuing jet was seen to contain liquid, which was sufficiently proved to be liquid hydrogen by the fact that it was so cold as to freeze liquid air and oxygen into hard white solids.
Though with this apparatus, a diagrammatic representation of which is shown in fig. The one important novelty, without which it is practically impossible to succeed, is the provision of a device to surmount the difficulty of withdrawing the liquefied hydrogen after it has been made. The desideratum is really a means of forming an aperture in the bottom of a vacuum vessel by which the contained liquid may be run out.
For this purpose the lower part of the vacuum vessel D in fig. With the liquefying plant above referred to liquid hydrogen was for the first time collected in an open vessel on the 10th of May In this way some 20 cc.
In subsequent experiments the liquid was obtained in larger quantities—on the 13th of June five litres of it were successfully conveyed through the streets of London from the laboratory of the Royal Institution to the rooms of the Royal Society—and it may be said that it is now possible to produce it in any desired amount, subject only to the limitations entailed by expense.
Finally, the reduction of hydrogen to a solid state was successfully undertaken in A portion of the liquid carefully isolated in vacuum-jacketed vessels was suddenly transformed into a white mass resembling frozen foam, when evaporated under an air-pump at a pressure of 30 or 40 mm.
But a year or so before hydrogen was obtained in the liquid form, a substance known to exist in the sun from spectroscopic researches carried out by Sir Edward Frankland and Sir J.
Norman Lockyer was shown by Sir William Ramsay to exist on the earth in small quantities. Dewar in expanded it from a pressure of atmospheres at the temperature of solid hydrogen without perceiving the least indication of liquefaction. Other investigators, however, took a different and more hopeful view of the matter.
Dewar, for instance Pres.Legislative Assembly of Ontario: Official Report of Debates (Hansard) Workplace Safety and Insurance Board and Workers' Compensation Appeals Tribunal Annual Reports Ontario Department of Lands and Forests: Resource Management Report Report of the Wartime Prices and Trade Board Ontario Fish and Wildlife Review Ontario Sessional Papers my_virtual_library.
META-INF/timberdesignmag.com-able-acea-aceae-aceous-ad-ade-aemia-age-agogue-al-ales-algia-ally-amine-an-ana-ance-ancy-androus-andry-ane-ant. The Project Gutenberg EBook of Encyclopaedia Britannica, 11th Edition, Volume 16, Slice 7, by Various This eBook is for the use of anyone anywhere at no cost and with almost no re.
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