Jlegulus of Arfentt. 329 



ready been mentioned among the iron or$s s 

 Species 20. 



SPECIES II. 

 Mineralized by the aerial Acid. 



Calciform wfenical Ore, natiye Calx ofArfenif, 

 Jlos arfenici, 



$. It is found either indurated in the form 

 of white opake, tranfparenj:, or femi-tranC* 

 parent cryftals, or in a loofe powdery ftate, 

 frequently mixed with native arfenic ; it is 

 volatil when heated, though lefs fo than the 

 regulus ; it does not detonate with nitre f 

 thpvjgh ar> effervefcence arifes. 



Its fpecific gravity is from 3,706 to 5,0005 

 it is foluble in about 70 or 80 times its weight 

 of water in the temperature of 60, or in 15 

 or 20 times its weight of boiling water ; the 

 folution turns tincture of turnfole red, and 

 fyrup of violets green ; it is fcarcely foluble 

 in the vitriolic acid, fomething more in the 

 marine, and mod perfectly in the nitrous di- 

 luted ; when in a powdery form, it is called 

 Jlos arfenici, and has been often taken for a 

 calcareous earth. 



6. White pyrites, which confifts- of the calx 

 pf arfgnic, mixed with fulphurated irpn, has 



been 



