1 68 Mayow 



that the water in which quicklime has been slaked is 

 impregnated with contrary salts and these combined 

 with each other, is clearly evidenced by the fact that 

 the alkaline salt of that water unites with any acid 

 salt whatever, and its acid salt with volatile salt, 

 without any effervescence or heat. 



But further, that the precipitation may be seen in 

 any liquid and that the liquid may become turbid, it 

 is indispensably necessary that what is precipitated 

 should be opaque and not transparent, in order that 

 as it descends it may fill the pores of the liquid and so 

 hinder rays of light from being transmitted through 

 them, as happens in the precipitation of iron or of any 

 other metal. For when iron dissolved by an acid 

 liquid is driven from its embraces, it is no longer 

 transparent but resumes its previous state, namely, 

 that of a solid and opaque body, so that the iron, as 

 it goes down, obstructs the pores of the liquid and 

 renders it turbid. 



But if that which is precipitated be nowise opaque, 

 but transparent or soluble in the liquid, then the 

 liquid in which the precipitation takes place will be- 

 come in noway turbid. Hence when oil of tartar /^r 

 deliquium is mixed with a solution of sal armoniac, 

 although the fixed salt of tartar absorbs the acid of 

 the sal armoniac and the volatile armoniac salt is 

 precipitated from its union with its partner, still the 

 liquid does not become in the least turbid, because 

 that volatile salt, in the course of its descent, dissolves 

 in the liquid and does not at all obstruct its pores. 

 Similarly, when an acid salt is precipitated from its 

 union with a fixed salt by the addition of a more 

 appropriate acid (as happens when the alkali of which 

 nitre partly consists leaves the nitrous acid and com- 

 bines with oil of vitriol poured upon it, or also when 



