VOL. XXII.l PHILOSOPHICAL TRANSACTIONS. 6l 1 



Observations on those Solutions and Fermentations, which may be called Cold. 

 And of a new Thermometer, from a Discourse made by M. Geoffroy, F. R. S. 

 to the Royal Academy of Sciences, April 1 1 , 1700. N° "ITA, p. QS 1 . 



The different researches I have made into the nature and properties of salts, 

 and the different experiments which I have tried, in examining their solutions 

 or mixtures in certain liquors, have given me occasion to observe, that the mix- 

 ture of the greatest part of the salts in several liquors is attended with a sensible 

 coldness, notwithstanding the prompt and violent fermentations which ensue on 

 many of these mixtures. I have distinguished these solutions or mixtures into 2 

 classes; the former comprehends all the simple cold solutions ; that is, such as 

 are not accompanied with any sensible fermentation ; the second takes in only 

 the cold ferments, or solutions of salts, which are attended both with a sensible 

 fermentation, and a coldness of the liquor. 



Class I. Of Simple Cold Solutions. — I put a pint of common water into a 

 phial, and an ordinary thermometer of 18 inches in the water, and so let it rest 

 for some time, to adapt itself to the temperature of the water. I afterwards put 

 into the water 4 ounces of sal ammoniac, and in less than a quarter of an hour 

 the liquor of the thermometer descended 1 inches and g lines. Observing the 

 same circumstances, I made the same experiment v/ith saltpetre, and the liquor 

 of the thermometer descended 1 inch 3 lines. The same experiment being made 

 with vitriol, the thermometer descended almost an inch. Sea-salt made the 

 liquor descend only 2 lines. All the alkali volatile salts cooled the common 

 water by their mixture, causing the thermometer to descend by some lines : but 

 I observed that they caused it to do so, more or less, according as they were 

 more or less purified ; and the salt of urine seemed to do so soonest of all. As 

 for the alkaline lixivious salts, they were so far from cooling the water, that 

 they heated it, more or less, according as they were more or less calcined. 



On the whole, we may observe, that the salts for heating the water, ought 

 to be purely alkaline ; for if they approach near the nature of nitre or sea-salt, 

 they heat the water but a little, or not at all, if they do not rather cool it. This 

 is also done very considerably by the salt of tamarisc, extracted from the lixivium 

 of the ashes of this vegetable. Sal ammoniac mingled with the acids of vegeta- 

 bles, as distilled vinegar, juice of lemons or verjuice, gave no signs of fer- 

 mentation, but cooled these liquors very much. An ounce of sal ammoniac, 

 cast into 4 or 5 ounces of distilled vinegar, causes the thermometer to descend 

 1 inches 3 lines. The same salt mixed with the juice of lemons, caused it to 

 descend 2 inches. And it does the same with verjuice. 



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