140 toem-ent o*- an akcient mosaic. ; 



iias always been Been alloyed with silver dr Copper, and friost 

 commonly with both, and with other metals al«6. The 

 gold that was the subject of the preceding ^xpei-jmeifits ap- 

 pears to have been alloyed with palladium ^lone. If it hid 

 been alloyed with any other metal, except silver or pldtin^, 

 the €X(>eriment No. 11 would have shown it; and silver 

 would have been discovered by the first experiment, and 

 platins by the fourth. 



Xill. 



Analysis of the Cement of an antique Mosaic^ found at Rome : 

 by Mr, D' ARciiTf *. 



EiSd!"* -**- ^^^ cement is of a yellowish white, very compact, with* 

 out grains, and pretty hard. It blackens a little in the fire. 

 Before calcination it effervesces briskly : but aft6f it has 

 been calcined, nitrous acid dissolves it without ev6lving any 

 carbonic acid. In the former case a few yellowish floCks 

 remain, and sojrve fragments of a reddish broWh coVoni", 

 but little corapdct, and resembling the porous lavas, or puz- 

 zolana. The yellowish flocks are destructible in the fire. 



Sulphuric acid precipitates nothirtg from these s6lution6^ 

 therefore they contain no lead. 



Ammoniac throws down only a little alumina and oxide 

 of iron. 

 Analysis of it. 5 gram. [77*29 gfs] of this cement, calcified under a rtttf- 

 fle for eight hours, no longer effervesced, and weighed Oiily 

 2*815 gr- [43*48 grs] ; which indicates in 100 parts 



56'3 of quicklime ; and 



43*7 of vegetable or animal matter and carbonic acid. 



10 grammes of this cement left 4*1 of carbonic acid, when 

 acted on by nitric acid. We have therefore in 100 parts 



59 of quicklime and animal of vegetable raattef, dtid 



4l of carbonic ncid. 



♦ Ann. de Chim. vol. LXXIV, p. 813. This cement was sent by Mr. 

 Belloni, Director of ttie Imperial School of Mosaic, who considered it 

 »3 one of the best cements the ancients had emi>loyed in the fabrication 

 ©f their mosaics, and of their pavements in compaitraent*. 



On 



