12 PHILOSOPHICAL TRANSACTIONS. [aNNO 1683-4. 



As to the increase of weight, we know how bodies deprived of some consti- 

 tuent parts by fire, (as quicklime and all calxes) slacken and imbibe something 

 from the air;* and the like is observed in the caput mortuum of salt, nitre, 

 alum and vitriol. Thus also, all fixed salts run into a fluid per deliquium; it is 

 the air, that in 7 years fully reimpregnates the earth, heaped up in the shade, 

 whence nitre was before extracted; it is the air that causes the efflorescence of 

 marcasites and vitriol-stones ; it is the air that by its acid turns the lead of old 

 buildings into cerusse, which without doubt increases in weight, (as that made 

 by fire does), which is asserted to be at the rate of 6 or 7 pounds in 100. 



Thus the increase and attractive power of solids is already put beyond ques- 

 tion ; but that liquids, such as seem saturated with their own moisture should 

 imbibe more from the air, is not mentioned by any author that I know of, ex- 

 cept the aforesaid learned person, who in his tract on aerial magnets advises 

 trials on the liquid preparations of vitriol : I have heard indeed some druggists 

 have accidentally taken notice of this increase in oil of vitriol, but the observa- 

 tion never was prosecuted so as to ascertain how much the said increase was, and 

 what the substance gained. The industrious chemist Mr. White, our uni- 

 versity operator, having a phial of that liquor unstopped and constantly running 

 over, first gave occasion to the following notes : but since from thence no true 

 estimate of the just increase could be collected, I hope it may not prove alto- 

 gether ungrateful to the curious to state what has occurred more particularly on 

 this subject. 



On the gth of Nov. l683, 3 drams of oil of vitriol, so far dephlegmated as to 

 burn or corrode a strong packthread asunder, was exposed to the air in a mar- 

 malade glass of 3 inches diameter, and placed in a nice pair of scales, in a room 

 where no fire nor sun came; its increase for 7 natural days, divided by less por- 

 tions of time, was according to the following table. 



« By " calxes" the author means metallic oxyds, as, by way of illustration, he afterwards men- 

 tions cerusse, an oxyd of lead ; but between metallic oxyds and quicklime there is no proper ana- 

 logy. In the production of metallic oxyds by the action of fire, it is true, as the author remarks, 

 that something^(oxygen) is absorbed from the air, whence there is an augmentation of weight; but 

 in tlie burning of chalk or limestone (carbonate of lime) there is something (carbonic acid gas) driven 

 off, the consequence of which is a diminution of weight. Thus the condition of the two products 

 (a metallic oxyd and quicklime) immediately after being subjected to a due degree of heat, is directly 

 opposite. If, however, the quicklime be subsequently exposed to the open air, it re-absorbs the prin- 

 ciple (carbonic acid gas) which had been driven off by tlie fire ; and in consequence of this re-absorp- 

 tion, it recovers, along with its former properties, its loss of weight. 



