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A is the receiver of aji air-pump, 

 furnished at the top with a collar and } jj < oa 

 sliding rod. BC is a small graduated a {t -r 1 [ 

 tube filled with the substance, the vo- '^ 

 lume of which is to be determined; Jtf/ , 

 is closed with a stopper E, perforated • * 

 with a hole of dimensions so small as " i , 

 to prevent any oi the salt rrom lai ms -' -• 

 out. D 13 a cup or mercury placeici 

 immediately below the graduated tub^ 

 C. The sketch indicates the position 

 of the apparatus on an air-pump when 

 the experiment is about to be perform- 

 ed. The receiver is then exhausted as 

 thoroughly as possible, and the indir 

 cation of the siphon-gauge is accu- 

 rately noted. The graduated tube 

 is then lowered by means of the sli- 

 ding rod until it touches the bottom 

 of the cup containing the mercury, 

 which, after the admission of air, flows into the tube until it 

 is filled. The whole contents of the tube are then thrown 

 into water, and the salt is washed away by decantation. The 

 mercury is dried by bibulous paper, and restored to the tube. 

 If the temperature be different from that which it possessed 

 in the first part of the experiment, it is restored to the origi- 

 nal temperature, or a correction is made for the difference. 

 It is now obvious that the space in the tube unoccupied byi 

 the mercury is that which was formerly filled with the salt;« 

 To this, however, must be added a slight correction for the 

 imperfect nature of the vacuum, which is not Torricellian, — 

 a correction which need not exceed g^o^^^ ^^ ^^^ volume 

 observed. With these preliminary descriptions and observa- 

 tions, we now proceed to describe the details of our experi- 

 ments, throwing them into various classified groups of salts, 

 for the purpose of easy reference. 



The first group described is remarkable for containing a 

 large amount of water of hydration. 



Sulphate of Copper, CuO, SO3 -f 5HO = 1 24-88.— The 

 third part of an equivalent of this salt, 41 '62 grains, dissolved 

 in 3140 grains of water at 32°, with an increase of 13*15, but 

 dissolved in water at 90°, with an increase of 15'0. a Ji ttioii 

 CuO, SO3 + 5HO, vol. in solution 45-0. >> rriv&b 

 ^jrHalf an equivalent of this salt, 62*44 grains, being immersed 

 hi a saturated solution, occupied the volume of ^^7' 7' water- 

 grain measures. ■MnUvr ■:. ;s)-iad /u»n> -■,<- 



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