Feb. 19, 1880] 



NA TURE 



387 



second part of the examination tkere will be two questions at 

 least in each branch of science included in the examination in 

 each paper. 



There are now about ten courses of professional and inter- 

 collegiate lectures announced at Cambridge for the benefit of the 

 selected Indian Civil Service Candidates ; so that Oxford, 

 Cambridge, and London are fairly in the field of competition in 

 educating men for this great field of labour. 



We notice with pleasure that the Cambridge Senate have 

 conferred the honorary degree of Master of Arts on Mr. 

 Patlison Muir, prelector in chemistry at Caius College. 



Mr. J.G. Fitch's lectures at Cambridge this term, on the 

 practice of education, are attended by between sixty and seventy 

 students, of whom about one-half are men. The new literary 

 schools are soon in use. There will be an examination for teachers 

 in June, under the Teachers' Training Syndicate, and certificates 

 will be granted for theoretical knowledge in teaching. Mr. Oscar 

 Browning will keep a register of all the university men who pass 

 the examination, and will act as a means of communication 

 between them and head-masters who require assistants. With 

 Ml the more confidence we may look forward to great 

 advantages from Mr. James Ward's lectures on the Theory of 

 Education next term, he having given high proof of ability as a 

 physiologist. 



The Cambridge Natural Science Board announces that Prof. 

 Hughes's lectures this term are on the Pre-Cambrian and Carbon- 

 iferous rocks, while in palaeontology, Mr. Tawney will lecture 

 on Trilobites. Mr. Walter Keeping, B.A., continues his 

 (open) lectures at Christ's College, on Rocks and Rock Masses, 

 their Formation and Metamorphosis. 



Mr. Hillhouse is lecturing on botany in the lectures for 

 women, and Mr. Walter Keeping on geology supplementing 

 Prof. Hughes's lectures. 



A new Cambridge medical association has been formed, and 

 has obtained permission to meet in the old anatomical schools. 

 livery effort will be made to render this association a most 

 valuable means of advancing the interests of medical science in 

 the University. 



Prof. Stuart and Mr. Garnett are the examiners in 

 mechanism and applied science for the year. 



The law on the constitution of the high council of education 

 in France is progressing favourably before the Senate. No 

 other members « ill be admitted than professional teachers, except 

 delegates of the five National Academies : Sciences, Beaux Arts, 

 Francaise, Sciences Morales et Politiques, Inscriptions et Belles 

 Lettres. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, January 29. — "A Note on Protagon." By 

 Arthur Gamgee, M.D., F.R.S., Brackenbury Professor of 

 Physiology in Owens College, Manchester. 



In this paper the author notices the allegations of Thudichum 

 that protagon is an impure body containing more than 1 per 

 cent, of inorganic matters, including no less than 076 per cent, 

 of potassium. 



He communicates a report from Prof. Roscoe, F.R.S., whom 

 he requested specially to determine the mineral impurities and 

 the amount of potassium in one of the samples of protagon, of 

 which the analyses had formerly been communicated to the 

 Royal Society. 



By means of the spectroscope Dr. Roscoe determined the 

 existence of a trace of potassium, which he estimated as equal 

 to one-twentieth of a milligramme in one gramme of protagon 

 (0*005 per cent. ). Further, he found that on ignition protagon 

 left a small quantity of fused metaphosphoric acid corresponding 

 to I 08 per cent, of phosphorus ; the mean quantity of phos- 

 phorus deduced from the observations of Gamgee and Blanken- 

 horn being I '068. 



"On the Physical Constants of Liquid Hydrochloric Acid." 

 By Gerrard Ansdell, F C.S., Chemical Assistant at the Royal 

 Institution. Communicated by Prof. Dewar, F.R.S. 



In continuation of my former experiments on the properties of 

 liquid acetylene gas, I have recently examined the physical 

 constants of liquid hydrochloric acid. The gas was made by 

 the action of strong sulphuric acid on dry chloride of ammonium, 

 being afterwards freed from sulphuric acid and dried before 

 entering the tubes. 



The Cailletet pump was used in the fame way as described in 

 my former paper, two iron reservoirs being used, one containing 

 the air manometer, and the other the tube with the gas to be 

 liquefied. 



Apart from the mere determination of the vapour tensions, 

 densities, &c, the ratios of the volume of saturated vapour to 

 that of the liquid was considered of the highest importance, as 

 from these numbers the latent heat of transformation and other 

 important data can be easily calculated. For these reasons the 

 gas was examined in rather a different way to the acetylene, the 

 volume to which it had been compressed at the point of lique- 

 fac ion (or the volume of the saturated vapour) at any given 

 temperature being first accurately determined, and then the 

 pressure increased until the condensed liquid entirely filled the 

 upper part ..f the tube. The volume of this liquid column was 

 then measured, so that a comparison between the volume of the 

 satura'ed vapour and the volume of the total condensed liquid 

 was obtained at each temperature. 



The re ults of the whole series of experiments are recorded in 

 a c indensed form in the following table : — 



' 37 ' 31 - ;4 ■■" 7'55 - iS-iS ... 29-8 

 3»i>9 



lyS ... 103-50 ... — L- ... S-35 

 5o l 9 



'2-39 ... 3775 



220 ... Sri9 ... _ qo6 ... 9-10 ... 8-92 ... 45-75 

 33-4 .- 5575 -. -^ .- .0-.2 ... 5-50 ... 58S S 

 44-S ... 36-34 ... -±- ... 11-96 ... 3-03 ... 75-20 



48-0 ... 3f33 ... — .. I2\X> ... 2'6l ... So'So 



I9760 



5056 ... 25-70 ... — ... 14-30 ... 1-79 ... 85-33 

 51-00 ... 2396 



In this table 



A = temperature of gas. 



B = volume of the saturated vapour at point of liquefaction. 



C = fractional volume of the gas at point of liquefaction in 

 relation to the initial volume under one atmosphere of pressure. 



D = volume of the condensed liquid. 



E — ratio of volume of liquid to that of the gas. 



F = 1 ressure in atmosphere. 

 The critical point was found to be 51 "-25 C. 



It will he seen from this table that the volumes of the saturated 

 vapours and liquid gradually approach each other as the tempe- 

 rature nears the critical point, and would undoubtedly become 

 identical, if the experiments could be carried on up to the critical 

 point. 



The rati'> between the volume of the saturated vapour and the 

 volume of the liquid at different temperatures decreases very 

 regularly until within about three degrees of the critical point, 

 where a singular point in the curve occurs, and the ratio 

 approaches unity with great rapidity. The v >lutne of the liquid 

 increases very regularly up to a temperature of about 48 C, and 

 at 51° C. , or within 0*25 of a degree of the critical point, the 

 distinction between the saturated vapour and the liquid vanishes, 

 as although liquid is plainly seen to condense on the surface of 

 the mercury, on increasing the pressure the line of demarcation 

 immediately disappears, and it is impossible to say wheth r the 

 tuhe is filled with the saturated vapour or the liquid itself ; here- 

 fore no r -suits could be obtained nearer the critical point than 

 about a f..urth of a degree. 



Avenarius, in a paper entitled " The Causes which dete mine 

 the Critical Point" ("Aca-l. Sci. St. Petersburg," 187-77), 

 made a number of experiment on ether, and cane to the con- 

 clusion that the volumes of the saturated vapour and of the 

 condensed liquid at the critical point were not identical. 



My own experiments appear to confirm his results, in so far as 

 it is evidently impossible to measure the relative volume of fluid 

 and ga- within le-s than a fourth of a degree of the critical 

 point, and at this place the volumes are certainly unequal. 

 This, however, does not disprove their identity as the critical 

 point. 



The density of the li ,uid at different temperatures was deter- 

 mined in the same way as described in my former paper, and 

 gave the follow ing numbers : — 



