VOL. XXII.] PHILOSOPHICAL TRANSACTIONS. 6l7 



in this space is rarefied by the exterior air which touches the bottle, it presses at 

 the same time the liquor e, and obliges it to rise through b in the tunnel bc. 

 On the contrary, when it condenses by the exterior cold, by not pressing the 

 liquor E, it permits that which is in the tunnel to fall. The readiness with which 

 the air condenses or rarefies by cold and heat, makes the effects of this ther- 

 mometer much more sudden than those of any other sort. Besides, the effects 

 of this are much greater, the air being more capable of a great rarefaction, or of 

 a great condensation, than any other liquor. 



As for the sensible heat of the vapours which rise from the mixture of sal 

 ammoniac with oil of vitriol, it is not difficult to find the cause, if we consider 

 that these vapours are only the most subtile and active parts of this mixture, 

 which the subtile matter raises with itself in crossing it. The motion of these 

 particles is free in the air ; and it is only more repressed by the two gross coagu- 

 lated particles. It becomes by so much the more violent, by how much it has 

 been retained and hindered for some time ; and is perceived by heat, which is 

 the ordinary effect of rapid and violent motion. 



I will relate another considerable experiment of the cold fermentation caused 

 by the mixture of sal ammoniac and oil of vitriol. If after having made the 

 mixture of 4 ounces of oil of vitriol, and an ounce of sal ammoniac, you throw 

 upon it a spoonful of common water, at the time when the fermentation is 

 strongest, the cold is greatest, and the thermometer falls with the greatest 

 quickness, the ferment ceases, and the cold changes immediately into a great 

 heat, and makes the liquor of the thermometer to rise very high. The reason 

 of this experiment may be readily conceived, if we consider, that the water 

 heating quickly and strongly by the oil of vitriol, produces here the same effect. 

 And this heat is sufficiently great at that time to destroy the cold of the coagu- 

 lated particles, the water of itself being otherwise proper to dissolve this coagulum. 



It remains that I give an account why sea salt heats with different acid 

 liquors; but as to that, we ought to inquire into the nature of this salt, which 

 would carry us too far. 



I will only say before I make an end, that I do not here pretend to enumerate 

 exactly all the cold solutions and fermentations ; I have related only the ex- 

 periments which I have made upon the salts and liquors which we oftenest use, 

 and which I thought most considerable. As to the reasons which I have given 

 of these cold solutions and fermentations ; I advance them only as conjec- 

 tures, which I submit to the judgment of philosophers, who understand these 

 matters better than I do.* 



* The reasons or explanations here given of the chemical phenomena mentioned ia this paper, are 

 •f no sort of value ; but they could not well be separated from the experiments themselves. 

 VOL. IV. 4 K 



