506 Dr. E, J. Mills on Elective Attraction, 



my former paper^ 1820 is a misprint for 1620. With reference 

 to the remark of Norwood about Vlacq's work, quoted in the 

 note on p. 301, I may add that I have since seen the first edi- 

 tion, 1631, and the third, 1656, in both of which the passage 

 in question occurs in the '^ advertisement to the Reader.^' It has 

 occurred to me that Norwood^s remark was intended to apply 

 rather to the prefixed Trigonometry &c. than to the Tables ; and 

 if this is the case, there is some justification for it. 



Trinity College, Cambridge. 

 October 17, 1872. 



LXI. Researches on Elective Attraction. 

 By Edmund J. Mills, D.Sc.^ 



" Jamne vides igitur tnagm primordia rerum 

 Referre, in quali sint ordine quseque loeata, 

 Et commista quibus dent motus accipiantque." 



Lucretius. 



THE following experiments had their origin in an attempt to 

 prepare nitrylic chloride by the action of phosphoric oxy- 

 chloride on plumbic nitrate. The reaction between these two 

 bodies takes place, according to the common statement f, in ac- 

 cordance with the following symbolic expression : — 



3Pb(NO^)2 + 2POCF = Pb3(PO^)2 + 6NO^Cl. 



Among other modes of verifying this equation, the examina- 

 tion of the residue left behind when excess of the oxychloride is 

 heated with the nitrate and then distilled off in a current of dry 

 air was resorted to as the most simple and obvious. The results 

 were found not to agree with the equation ; and after three 

 nitrates had been tried, a law of chemical attraction became evi- 

 dent, rendering the reaction worthy of pursuit for its own sake, 

 although as a practical source of nitrylic chloride it had failed 

 entirely. The nature and mode of establishment of this law 

 constitute the subject of the present memoir. 



When a nitrate is treated with phosphoric oxychloride as 

 already described, the residue contains a chloride and a phos- 

 phate, — the latter being probably always phosphorylic phosphate 

 (PO . PO^] or phosphoric pentoxide. The ratio between these 

 products is sensibly constant, and will be designated by a special 

 symbol, in accordance with the following understanding : — 



weight of chlorine 



Q\ w^eight of chlorine 



« = weight of phosphoric oxide " weight of phosphoric oxide 



p2 05 



* Communicated by the Author. 



t Compare Watts's ' Dictionary of Chemistry,' vol. iv. p. 17. 



