1821.] ' Atomic Weight of various Metals and Acids. 139 



water, and saturated with ammonia : 20-75 grs. of dry nitrate of 

 lead were dissolved in another portion of water, and the two 

 solutions mixed. Tartrate of lead precipitated abundantly, and 

 the supernatant liquor being tested with sulphate of soda and 

 nitrate of lead exhibited no traces of containing either oxide of 

 lead or tartaric acid. The tartrate of lead thus formed being 

 washed and dried in a temperature not exceeding 100° weighed 

 22*4 grs. It was obviously a compound of one atom acid + one 

 atom oxide of lead. Now 



1 atom acid weighs 8*375 



1 atom oxide of lead 14-0 



22-375 



So that the weight exceeded the truth only by 0025 gr. or not 

 more than 1000th part. It is clear from this, that tartrate of 

 lead, if we dry it at the temperature of 212°, will contain no 

 water. This gives us the following formula for determining the 

 quantity of tartaric acid in any soluble tartrate. Dissolve the 

 salt in water, and precipitate the acid by nitrate of lead. Wash 

 the precipitate, and dry it in the temperature of 2 12°. Weigh it, 



8*375 



and multiply the weight by ; - , or by 0-374, the product is the 

 quantity of tartaric acid contained in the tartrate. 



IX. Citric Acid. 



From the experiments made en this acid by Berzelius, there 

 is reason to conclude, that the atomic weight of it is 7*25, and 

 that the crystals are composed of 1 atom acid -f 2 atoms water^ 

 or of 



Acid 7-25 



Water 2-25 



9-5 



If this supposition be true, the equivalent number for th e 

 crystals of tartaric acid and citric acid is the same, or 9-5. 



My attempts to verify this opinion by decomposing citrate of 

 ammonia by means of muriate of lime did not lead to satisfac- 

 tory results; I shall not, therefore, give an account of them. 

 The following experiment I consider as decisive : 



9'5 grs. of the crystals of citric acid were dissolved in water 

 neutralised with ammonia, and then mixed with a solution of 

 20-75 grs. of nitrate of lead. It is worthy of attention that no 

 precipitate appears, neither when citrate of ammonia is mixed 

 with muriate of lime, nor with nitrate of lead. But when the 

 mixture is slowly evaporated to dryness, the citrate of lead gra- 

 dually separates, and is not again dissolved, though the dry 

 residue be digested in distilled water. A portion of this clea* 



