174 



A TREATISE ON METAMORPHISM. 



Chemical relations of silicon and carbon — Continued. 



KAl(Si0 3 ) 2 leucite 



AlA)-Si=0 



O. ^Natural metasilicates. 



^Si=0 



BegAl^SiOa^ beryl, 

 etc. 



(normal salts) 

 ,0-Na 

 0=C( 



x O-Na 



0=C( x Ca 



(acid salts) 

 ,/ 0H 



0=Cs 



o=c 



ONa 

 OH 



:ca 



0=C 



OH 



H 2 Si 2 5 disilicic or dimetasilicic acid. 

 .OH 

 0=Si< 



0=Si( 



x OH 

 Si : : : 2 : 7 for basic salts. 

 Si : O : : 2 : 5 for acid salts. 



Not known in free state. 

 LiAl (Si 2 5 ) 2 petalite. 



H 6 Si,0, diorthosilicic acid 



/(OH), 

 SiC 



<° 



X (OH) 3 



H 4 Mg 3 Si 2 9 serpentine (normal salt). 

 ,0— Mg— OH 



.H 2 C 2 5 dicarbonic or pyrocarbonic acid. 

 /OH 

 0=C( 



o=c( 



N 0H 

 Known only in salts, as C 2 3 (NaO) 2 , produced by 

 heating the acid salt. 



.The corresponding carbon acid does not exist. 



Si^O-H 



»Mg 

 Si-O/ 

 •^0-H 

 x 0-Mg- 



OH 



H,CaSi 2 O e +H 2 okenite (acid salt). 



H 4 Si 3 8 polysilicic acid or trisilicic acid 



(May be considered as metasilicic acid plus 



disilicic acid. ) 



/OH 



Si=0 



>° 

 Si=0 



Si4(0H) 3 



(neutral salts of trisilicic acid) 

 KAlSi 3 8 orthoclase. 

 NaAlSi,0„ albite. 



The corresponding carbon acid does not exist. 



