270 On the Definite Proportions in luhlch the [Aprii,, 



sugar of milk 40 + 5 C + 10 H, or, according to the compo- 

 sition of saccolate of ammonia, 8 O + 10 C + 16 H, which con- 

 Btitute per cent. 



Hydrogen G*385 



Carbon 45-267 



Oxygen 48'348 



100-000 



Sugar of milk then contains more carbon and less oxygen than 

 common sugar. This explains why, when we burn the compound 

 of these two bodies with oxide of lead, the first reduces much more 

 lead than the other. We understand also why sugar of milk is 

 more easily carbonized than common sugar. 



12. Gz/OT ylrabic.—\ mixed caustic ammonia with a filtered and 

 boiling solution of gum arabic. I then mixed it with a solution 

 of subnitrate of lead, likewise boiling hot. I took care not to add 

 enough to precipitate the whole of the gum. I decanted off' the 

 liquid from the |)recipitate, which 1 washed repeatedly with boiling 

 water. I then subjected it to pressure, and dried it in a vacuum, 

 finally exposing it to the heat of 212°. 



When analyzed by combustion, the gummate of lead left for 

 residue 38-25 per cent, of oxide of lead. It was therefore com- 

 posed of 



Gum 61-75 100-000 



Oxide of lead 38-25 62-105 



. 100-00 



The oxygen of these 62-105 of oxide of lead is 4'44. To ob- 

 tain a subgummate of lead I digested a solution of gum with oxide 

 of lead. A sul)gummate was formed, very heavy and coherent; 

 but which could not be entirely separated from the gummy liquid. 

 Of course 1 was unable to analyze it. 



0-648 of gummate of lead, equivalent to 0-4 of gum, produced 

 bv combustion 0-2297 of water, and 0-617 of carbonic acid, equi- 

 valent to 6'75 per cent, of hydrogen, and 41-956 of carbon. 



0*4 of gum arabic, in the state of a fine powder and dried in a 

 vacuum at the tem))eiature of 212°, produced by combustion 0-231 

 water and 0-619f> of carbonic acid, equivalent to 6-788 per cent, 

 of hydrogen and 4 1*906 of carbon. Hence it apppears, that dried 

 fi;um' arabic contains no water; for it is probable that gummate of 

 lead cannot retain water with greater force than the other conilii na- 

 tions liaving oxide of lead for their base. Gum arabic is then 

 composed as follows : 



Hydrogen 6-788 



Carbon 41-90fi 



Oxygen 51 -30(> 



