WITH THE MARINE ACID. 335 



as to carry off all the fuperfiaous water ; the a- 

 cid is carefully to be preserved and retained. 



S ix. The external AWmrancc of corrojtve mer- 

 curial Sublimate. 



Co!\Rosiv: mcrcvrkl fublimte is collected 

 cither in the form of claftic fmall needles, or a 

 (Bryftalline mats. On being difTwlved again, and 

 the water afrcr.vanls evaporated, it accretes in- 

 to various lvinI-i of cryllal*?, according to the 

 difference of nrticu!iu circuinflances. If boil- 

 ing water is taturatui \vit.h it, and the folutiou 

 cxpofcd immediately to ihecold air, nccdlc-likc 

 cryflals are produced. It' the evaporation is con- 

 dmlcd gradually, \ve perceive cryiials in the 

 fhape of cubes or oblique parallelepipeds *. Mo- 

 net dcfcribc? cryflals uii('er yet other appear- 

 ances. JUit fuch is the nature of falts that each 

 affects a certain form peculiar to itfclf, a r > an 

 architypc, unlefs its courfe is interrupted by the 

 accidental iinpulfe of external things*. Cor- 

 rofivc mercurial iubliniate is governed by the 

 the fame law. In general, if fallicient fpacc is 

 allowed it, it aflumcs the form of quadrangular 

 prifms, with alternate narrower tides, and with 

 uniform terminations of two inclined planes. 



ix. 



* Mem. dc 1'acod. dti fcienccs, 1753. 

 A See Di He nation eo the furmi of cry Hals, F. flays, r ii. 



