s SS l ]

A

r '

Specific Gravity

Platinas

IRON

By fcxp.7,100

By Laic.

Difference

Gravity

resulting

Platina i, Iron 1,295

9'9I7

9>5 M

,406 +

20,403

Platina 1, Iron 3,333

8,700

8,202

,498-j-

Z4'963

Platina 1, Iron 5,150

8,202

7,842

,360+

40,95!

Platina 1, Iron 10 - -

7,862

7-496

,366 +

Platina 1, Iron 12 - -

7,800

7-4Z2

,368-j-

The compositions with silver have afforded a proof ofthe diminution of gravity from mixture, or of the m^fsbeing dilated, from the action of the ingredients upon oneanother, into a larger volume than they occupied separately.The above compositions with iron seem to be as strikinginstances of a contrary effect : the gravity of the two lastof them is such, as no substance, however ponderous, couldpossibly produce by the simple apposition of its own partsto those of the iron; for it appears in the calculation, thatthe platina and iron together occupy less volume than eventhe iron by itself.

Mr. Scheffer very ingeniousty accounts for this remark-able phenomenon from a singular property of iron. Whenmetals are deprived by calcination of their phlogiston or in-flammable principle, their absolute weight is increased:iron, by complete calcination, receives an augmentation ofone third of its weight. Cast iron has this particularity,that it can bear. a considerable dissipation of its phlogiston,without calcining, or without losing its metallic form; and.in proportion to this dissipation its absolute weight is in-creased. Now, as the above ponderous mixtures weremelted without any inflammable addition, he thinks a part'of the phlogiston of the iron must neceflarily have beenburnt out in the fusion, and the. metal of consequence ac-quired an additional weight; but that, as no increase was-

obfervecL.