472 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1788. 



Spirit of wine. 



The specific gravity of the spirit of wine em- 

 ployed was .829 at 62°. It depressed the freez- 

 ing point according to the following table : The 

 total difference between the calculation and ex- 

 periment, on a reduction of the freezing point 

 from 244- to 4°, is f of a degree ; but the inter- 

 mediate points are very irregular, and is an op- 

 posite sense, as if the ratio were decreasing. It 

 seems more probable, that some inaccuracy in 

 the experiments, perhaps owing in part to the evaporation of the spirits, should 

 be the occasion of this, than that there should be such an irregularity in the law. 

 If any person should allege, that the difference between the observed and com- 

 puted freezing points in the foregoing tables is not sufficient to establish the in- 

 crease of ratio. Dr. B. can only reply, that it appears to him greater than can 

 reasonably be ascribed to error in the experiment ; especially as similar experi- 

 ments with neutral salts, not conducted more attentively, agreed so well together 

 in pointing out a different law. It must be allowed however, that the experi- 

 ments do not show any increase of ratio, except in the vitriolic and nitrous acids, 

 salt of tartar, and, with more ambiguity, in spirit of wine ; from analogy only he 

 suspects it to take place in the other acids, and in the mineral and volatile alkalis 

 provided they are caustic. That a different law from what prevails in the neutral 

 salts should take place with these substances, seems not surprizing, when it is 

 considered how much stronger attraction they show for water, and how much less 

 limited the proportion is in which they will unite to it : for the same reasons, he 

 should not think it extraordinary, if deliquescent salts, combined with water, 

 should be found to observe the same increasing ratio in depressing the freezing 

 point. 



Dr. B. concludes this paper with the account of an experiment to determine 

 the effect of salt on the expansion of water by cold. Pure water begins to show 

 this expansion about the temperature of 40°, that is, 8° above its freezing point. 

 He put a solution of common salt, in the proportion of 4.8 parts of water to one 

 of the salt, and consequently whose freezing point was 8f°, into an apparatus he 

 had used for other experiments of the same kind ; and found that the solution 

 continued to contract till it was cooled to 17°, but had sensibly expanded by the 

 time it was cooled to 1 5. Suppose the expansion to have begun at l6-§-°, it would 

 iae just 8° above its new freezing point. Hence we have reason to conclude, as 

 far as one experiment goes, that the combination of a salt with water has no other 

 effect on its quality of expanding by cold, than to depress the point at which 

 that quality begins to be sensible, just as much as it depresses the point' of 

 congelation. 



