282 Dr. Piii&sTr,EY*s Uxperlmenh and Ohfervatiom 



meaflire, of which one-fifth was fixed air, the refiduum wag 

 quite as pure as tiie air with which I began the experiment, the 

 teft with nitrous air, in the proportions above-mentioned,, 

 giving .4 in both cafes.. To what circumftance the. difterence; 

 mipht be owina: I c.annot tell. 



In thefe experiments the fixed.air mufi, I prefume, have been- 

 formed by the union of the phlogiflion from the iron and the, 

 dephlcgiilicated air in which it was ignited ; but the quantity) 

 of it was very fmall in proportion to the air which had difap^- 

 peared, and at. that time I, had no fufpicion that the iron, which. 

 liad been melted, and gathered into round balls, could have, 

 imbibed it; a melting heat having been fufficient, as I had. 

 imagined, to expel, every thing that was capable of afluming 

 the form of air from any fubflance whatever. I was therefore; 

 Intirely at a iofs about what muil: have become of the. air. 



Senfible, however,, that fuch a quantity of air muft have, 

 been imbibed hy fo met hing to w^^iich it mu ft have given a, very 

 perceivable addition of weight, and feeing . nothing elfe that 

 could have imbibed it,, it occurred to ma to weigh the calx, into, 

 which the iron had been reduced ; and I prefently, found, that 

 the dephlpgifticated air had adually been' imbibed by the melted 

 iron, in the fcjme manner as inflammable air, ia my former, 

 experiments, had been imbibed by the melted calces of metals, 

 however impoffible fuch an abforption might have appeared to 

 vat a priori. In the firfl: inftance, about twelve ounce mea-- 

 fures af dephlogiliicated air had difappeared, and the iron had 

 gained fix grains in weight. Repeating the experiment very, 

 frequently, I always found, that other quantities of iron, 

 treated in the fame manner, gained fimilar additions of weight,, 

 which was always very nearly that of the air which haddif-^ 

 appeared, . 



This 



