CHEMICAL EXPERIMENTS. 3Q1 



tifal lemon-yellow cryftals, which could not be obtained co- 

 lourlels, by repeated folutions and re-cryftallizations. But 

 after boiling them with charcoal powder, the fluid palled co- 

 lourlefs through the filter, and yielded pure benzoic acid in 

 the form of filky needles, weighing 23 grains. 



18« Camphor does not move upon Water at low Temperatures — 

 Phqfphorus moves upon Mercury, 



If a bafon of water, upon which fmall fragments oi camphor Camphor mo- 

 are in rapid motion, be fuddenly transferred into a freezing . tlon,efs on * ater 



1 J ° in a very cold 



mixture, the rotatory motion of the atoms of camphor inftantly atmofphere. 

 ceafes. 



If a cylinder of dry phofphorus be fcraped with a knife over Phofphorus 

 a i'aucer containing mercury free from duft, &c. the fmall ™* e . s on ■*• 

 particles of phofphorus which are detached, and fall upon the 

 quickfilver, fpin in a fimilar manner like thofe of camphor 

 placed upon clean water. 



Camphor, benzoic acid, mulk, caftor, civet, aflafoetida, but camphor, 

 vanilloe, and various other odoriferous iubitanees, remain mo- &c ' do not * 

 tionlefs when placed upon this fluid. 



19. Frogs change their Colour, and decreafe in Size, zvhen fecluded 

 from Light, and die zvhen fuddenly expofed to vivid Light. 



A number of male frogs of the largeft fize, and of a beau- Frogs become 

 tiful yellowifh brown colour, which had been kept for upwards "■£ and ,maller 



c r . . r rr by keeping m 



of fix months in a refervoir, fituated in a dark place, loft their the dark. 

 colour during that time, became perfectly black, and had de- 

 •creafed in fize to lefs than one half. A number of thefe ani- Light kill* them 

 mals, which were very brilk, and apparently in a good ftate 

 of health, were expofed to the rays of the fun, in order to fee 

 if they would regain their colour. They all died, during the 

 •experiment, in about three hours. The galvanic influence and deftroys ail 

 could not ftimulate their dead mufcles into aftion. irritability. 



A frog, which had eicaped, was found in a veflel contain- A frog converted 

 ing a concentrated folution of potafli, freed from carbonic acid, ^^^3^. 

 in which, from the time of difcovery, he could not have re- 

 mained longer than three hours. The animal was much dif- 

 torted, and converted into a flefh-coloured gelatinous mafs. 

 It was beautifully tranfparent, and twice its natural fize. 

 On pouring boiling water upon it, the whole was diflblved 

 into a jelly. 



Frogs 



