February 8, 1906J 



NA TURE 



355 



and for power may not be reduced also, so that while the 

 flame-lighting power may be reduced without much detri- 

 ment, the consequent fall of heating-power may be a 

 serious loss to the public. In the London Gas Act, 1905, 

 such risk has been met by the obligation to test the calorific 

 value of the gas for information only, but no penalties are 

 incurred, even though the gas should prove to be of much 

 less heating value than it has been. 



The gas referees have therefore had the question of a 



suitable calori- 

 meter before 

 them, and in the 

 Notification " 

 issued 

 January 1 



P- .273) 

 calorimeter 

 signed by 

 Boys, who is 

 one of them, is 

 prescribed for 

 use in official 

 testings. 



The calori- 

 meter in ques- 

 tion is of the 

 Hartley type, i.e. 

 a stream of 

 water constantly 

 passes through 

 the instrument, 

 and in so doing 

 it is raised in 

 temperature by 

 the heat pro- 

 duced by the 

 combustion of a 

 stream of gas. 

 The observations 

 available enable 

 the observer to 

 ascertain the 

 calorific value of 

 the gas. 

 of this class is the 

 relation to this that 



Fig. 



The best known instrument 

 Junker calorimeter, and it is 

 the new features introduced by Mr. Boys are best de 

 scribed. From the accompanying figure it will be seen 

 that the gas is burned at two small union jets instead of 

 in the usual long Bunsen flame. The hot gases rising into 

 the bell h descend outside the chimney E through the wires 

 of the inner coil M. This and the outer coil n are made 

 of the well known motor-car radiator tube invented by 

 Mr. Clarkson. The circulating water enters the outer coil 

 at the union o, and leaving the inner coil enters the space 

 above the bell it. where it circulates between two dished 

 plates and then leaves at the union p. The two lower 

 turns of the Clarkson tube are immersed in a condensed 

 water bath with an overflow f, which may be turned in 

 any direction. This water bath serves to keep the chimney 

 cool enough not to burn, but not cool enough to cause 

 condensation to occur on the inner surface. One result 

 of this construction is the slow passage of the products 

 of combustion through the instrument and the small re- 

 sistance they encounter. Hence the instrument need not 

 be more than a foot high. The circulation of the water 

 through the instrument strictly in series in every part 

 prevents the formation of pockets or streaks of warmer 

 water and consequent spasmodic changes of the outlet 

 thermometer reading, and such small changes as might 

 remain are almost entirely destroyed in the temperature 

 equalising chamber above the bell H. The result is that, 

 with a rise of temperature of 23 C, the variations do not 

 exceed two or three hundredths of a degree, and even this 

 appears to be largely due to friction in the meter in- 

 sufficiently corrected by the governor. 



Five minutes after lighting the gas the outlet thermo- 

 meter is within 6 per cent, of its ultimate rise; in ten 

 minutes it is within 2-2 per cent., and in fifteen minutes 

 it is less than J per cent. In this and other respects the 

 gas examiner who will have to use the instrument will 



find that not only accuracy, but his convenience lias been 

 studied. 



One feature is .mum. peculiar. While hitherto gas calori- 

 meters have I" -'ii Idered up so .1- to be of the nature 



ol mystery boxes, this can be seen in its essential features, 

 while it can be completely taken to pieces in a lew minutes 

 for examination ol every part. 



After use the mil system is lifted mil of the outer vessel 

 by the lid and is then immersed in a dilute solution of 

 bicarbonaP . as to neutralise the weak sulphuric 



acid condenser upon the metal and prevent it and its dis- 

 solved crxu^ln from prematurely destroying the metal-work 

 . The instrument 'is made by Messrs. Griffin 



ELECTRIC PRODUCTION OF NITRATES 

 FROM THE ATMOSPHERES 

 S the demand of the white races for wheat as a food- 

 stuff increases, the acreage devoted to wheat growing 

 increases, but at a less rapid rate; and being limited by 

 climatic conditions will in a few years, perhaps less than 

 thirty, be entirely taken up. Then, as Sir William Crookes 

 pointed out in his presidential address in 1898, there will 

 be a wheat famine, unless the world's yield per acre (at 

 present about 127 bushels per acre on the average) can 

 be raised by use of fertilisers. Of such fertilisers the chief 

 is nitrate of soda, exported from the nitre beds in Chili. 

 The demand for this has risen from 1,000,000 tons in 1892 

 to I ,543. I2 o tons in 1905, and the supply will at the present 

 rate be exhausted in less than fifty years. Then the only 

 chance of averting starvation lies, as Crookes pointed out, 

 through the laboratory. 



In 1781, Cavendish had observed that nitrogen, which 

 exists in illimitable quantities in the air, can be caused to 

 enter into combination with oxygen, and later he showed 

 that nitrous fumes could be produced by passing electric 

 sparks through air. Although this laboratory experiment 

 had undoubtedly pointed the way, though the chemistry of 

 the arc flame had been investigated in 1880 by Dewar, and 

 though Crookes and Lord Rayleigh had both employed 

 electric discharges to cause nitrogen and oxygen to enter 

 into combination, no commercial process had been found 

 practical for the synthesis of nitrates from the air until 

 recently. 



After referring, in passing, to the tentative processes of 

 Bradley and Lovejoy, of Kowalski, of Naville, and to the 

 cyanamide and cyanide processes, attention was directed 

 to the process of Birkeland and Eyde, of Christiania, for 

 the fixation of atmospheric nitrogen, and their synthetic 

 production of nitrates, by use of a special electric furnace. 

 In this furnace an alternating electric arc was produced at 

 between 3000 and 4000 volts, but under special conditions 

 which resulted from the researches of Prof. Birkeland, the 

 arc being formed between the poles of a large electro- 

 magnet, which forced it to take the form of a roaring disc 

 of flame. Such a disc of flame was shown in the lecture 

 theatre by a model apparatus sent from Christiania. In 

 the furnaces, as used in Norway, the disc of flame was 

 4 feet or 5 feet in diameter, and was enclosed in a metal 

 envelope lined with firebrick. Through this furnace air was 

 blown, and emerged charged with nitric oxide fumes. 

 These fumes were collected, allowed time further to oxidise, 

 then absorbed in water-towers or in quicklime, nitric acid 

 and nitrate of lime being the products. The research 

 station near Arendal was described, also the factory at 

 Notodden, in the Hitterdal, where electric power to the 

 extent of 1500 kilowatts was already taken from the Tinn- 

 foss waterfall for the production of nitrate of lime. This 

 product in several forms, including a basic nitrate, was 

 known as Norwegian saltpetre. Experiment had shown 

 thai it was equally good as a fertiliser with Chili salt- 

 petre, and the lime in it was of special advantage for 

 certain soils. The yield of product in these furnaces was 

 most satisfactory, and the factory at Notodden — which had 

 been in commercial operation since tie- spring of 1905 — was 

 about to be enlarged ; the neighbouring waterfall of 



1 Abstract of a discourse delivered at ihe Royal Institution on Friday, 

 February 2, by Prof. Silvanus P. Thompson, F.R.S. 



N-O. Ii 



VOL. 



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