COLD. 



735 



z 



cotiol. 



<Vd. A cold still more intense than can be procured by any 



s ~- "V"'' of the freezing mixtures mentioned in the preceding Ta- 

 Mr Hut ble has lately been obtained by Mr Hutton, a gentleman 

 ton' expe- in Edinburgh. He has not thought proper to commu- 

 riments on nicate to the public the processes of refrigeration which 

 * r *~ l he has employed ; but the result* of the cold he obtain- 

 ed, indicate a much greater reduction of temperature 

 than has hitherto been known. 



" Directing my attention to this subject," says Mr 

 Hutton, " in the summer of 1810, a method occurred to 

 me, by which I imagined a greater degree of cold might 

 be produced than had hitherto been obtained. Although 

 the power of this method appeared in theory almost in- 

 definite, yet it was easy to foresee, that in practice many 

 circumstances might at first concur to set limits to its 

 application; from the nature of these circumstances, how- 

 ever, it was to be expected that some of them might be 

 considerably modified, and many of them might in time 

 be altogether removed, and thus the practice made in 

 ..ome degree to Approximate to the theory. 



At the time this method occurred to me, the pressure 

 of my professional avocations did not allow me to prose- 

 cute it ; but, as I anticipated some leisure in the follow- 

 ing autumn, I immediately began to provide at any lei- 

 sure moments I had, such apparatus as I considered ab- 

 solutely necessary, or was most likely to be useful. The 

 little dependance, however, whicli is to be placed on ge- 

 neral reasoning on such subjects, and the apprehension 

 that the method might have been previously tried, and 

 found insufficient by others, prevented me from providing 

 any very extensive apparatus. 



My first experiment was tried in the following autumn. 

 The thermometer was filled and sealed by myself. The 

 tube was previously tried by the common method, and 

 found, as nearly as such tubes are commonly to be met 

 with, of equal calibre throughout. The spirit with which 

 it was fiiled, was prepared by Richter's process, and af- 

 terwards re- distilled by itself. Its specific gravity at 62 

 was 798. The points 60 and 100 were determined by 

 a mercurial thermometer, which had been made with the 

 usual precautions; the interval was divided into four spa- 

 ces, each of which, of course, corresponded to 10 ; the 

 part of the stem below 60 measured nearly 18 of these 

 upacci. A mark wai> made at every space, till, on arri- 

 ving at the end of the 17th, the giaduation could not be 

 carried farther. This point, of course, corresponded to 

 + 6O 170 = 1 10 of Fahrenheit's scale. 



This thermometer was exposed to the cold produced 

 by the method alluded to, and after some time was exa- 

 mined, when the alcohol was found to have passed all the 

 marks, and was obviously sunk within the ball of the 

 thermometer. A slight degree of discoloration was ob- 

 servable. The thermometer was replaced, and examined 

 about five minutes afterwards, when the ball of the ther- 

 mometer was found broken, and crystals adhered to the 

 fragments. 



1 next took a glass tube, about 3-lOths of an inch in 

 diameter, and scaled at one ei:d ; into this I poured alco- 

 hol till it stood in the tube 1 lOths of an inch deep, and 

 then exposed it lo the cold, produced as before ; after 

 some time, it was so completely solid, that on inverting 

 the tube it did not drop, and only a very minute stream 

 was perceived to gliuV niowly du >vn the inside of the tube ; 

 'when this stream hid reached nearly the middle of the 

 tube, i!he whole suddenly fell out, and, pitching in a 

 glas-, was broken into several pieces, which quickly 

 melted. 



This experiment wag several times repeated, but by al- 

 lowing the alcohol to remain a little longer exposed to 



the cold, it became so completely solid, that, on inverting Cold. 

 the tube, not the least portion of fluid could be percei- "~ "v ' 



ved to separate from the mass. r , 



.. .. . , . . r ton - expc 



In order to be as certain as possible ot the strength ot r ; ments on 



the alcohol I employed, I again took its specific gravity, the free- 

 and the result corresponded with what I before obtained. 7,mp of al- 



These experiments, therefore, left m. j no room to doubt cohoU 

 that I had frozen alcohol, which, at the temperature of 

 C2, is of the specific gravity 798. 



Being appointed (by the Edinburgh Institute) to de- 

 liver the course of lectures on chemistry for the session 

 1810-11, I had nj leisure at that time to pursue 

 experiments. They were resumed, however, in tlu 1 au- 

 tumn of 1811. The second experiment was repeated and 

 varied, and tolid masses of alcohol of some magnitude ob- 

 tained. Some of these I soldered together, using as a 

 hot bolt a rod of frozen mercury, and sometimes a straw 

 cooled down to a very L>w temper .iture. 



It now appeared to me to be an object of some impor- 

 tance, to ascertain the form of the crystals which this 

 substance assumes. This I found attended with some 

 difficulties which I did not anticipate, and attempts to 

 overcome them, have led to the discovery of some facts 

 which I did not at all expect 



The common masses exhibited crystals of different 

 forms ; two kinds appeared to predominate, and each was 

 tolerably distinct in its kiud, but it was not very eaay to 

 perceive by what increments or decrements the one could 

 be supposed to pass into the oth^r ; a rather casual cir- 

 cumstance, however, explained the source of this variety. 

 Attempting to freeze alcohol by a modification of the ge- 

 neral process, which I conjectured w.uld yield more re- 

 gular crystals than the common method, 1 observed, that 

 before crystallizing, the alchohol separated into three 

 very distinct strata, the uppermost was of a pale yellow- 

 ish green, while the second was of a very pale yellow 

 colour. Both these strata were very thin, the la^t men- 

 tioned was rather the thickest ; the lowermost stra uin 

 was nearly transparent and colourless, and very greatly 

 exceeded the other two in quantity. After allowing a 

 part of the lower stratum, which I conceived to be the 

 pure -alcohol, to freeze, I attempted to pour out the ie- 

 mainder, but was prevented by the upper strata, wnich 

 proved to be solidified. The lowermost of these two 

 strata bore some marks of crystallization, the upper had 

 none, and proved so firm as to resist a straw, with which 

 I attempted to perforate it, to open a passage for the 

 sublatent liquid. On removing part of these superior 

 strata, and decanting the remaining fluid, the crystals of 

 the lower stratum appeared very distinctly to be rect- 

 angular prisms of equal plants, a few of them on one 

 side of the glass surmounted by quadrangular pyra- 

 mids, but most of them by dihedral summits. This ex- 

 periment I repeated several times, and the results coin- 

 cided. 



In order to ascertain whether these phenomena arose 

 from a decomposition of the alcohol, or from the separa- 

 tion of foreign substances previously held by it in solu- 

 tion, the products of several of thete experiments, were 

 mingled together in a stoppered matrast ; the whoie was 

 then raised to the temperature of about 120, by a wa- 

 ter bath of that temperature. The substance-storming 

 the different strata united together, and formed a colour- 

 less liquor, which had the specific gravity and all the 

 other properties of the alcohol from which it was obtain- 

 ed. This experiment was repeated several times, and the 

 results were uniform, affording sufficient evidence that the 

 alcoh.il had not been decomposed by thia process, but 

 that the superior strata consisted of foreign substances 



