0-31 Oxalic Acid. 103 



II. yilhaline and Earthy Oxalates. 

 1. The preceding experiment gives us likewise the com- 

 position of oxalate of lime, This salt, when merely dri^d iq, 

 the open air, still retains a portion of water which may be 

 driven off by artificial heat. It is necessary to know thai it 

 parts with this water witii considerable difficulty, so that a 

 long exposure on the sand or steam bath is necessary to get 

 it thoroughly dry. It afterwards imbibes a little water if it 

 be left in a moist place. Well dried oxalate, we have seen, 

 is H compound of 



Acid 4 5 or per cent, 62"5 acid. 



Base 27 - - 37*5 base, 



72 100 



Though the oxalate of lime dried spontaneously can 

 scarcely be considered as always in the same state, yet as the 

 difference in the portion of water which it retains is not 

 great, provided it be dried slowly in the temperature of 60'', 

 and in a dry place, it may be worth while to state its com- 

 position. It is as follows : 



Acid 43 or per cent, 59-2 acid. 



Base 2 7 - - 3o-5 base. 



Water -1 - - 5-3 water. 



76 100-0 



When rapidly dried, as by pressing it between the folds 

 of filtering paper, it is apt to concrete into hard lumps, 

 •which retain more n)oisture. In tliis state I have sometimes 

 seen it retain 10 per cent, of water after it appeared dry. 



mentioned incidentally, that the crystals of oxalic acid contain about half 

 their weiglit of water. He dissolved 100 parts of ciiichonate of lime in v/ater, 

 and precipitated hy means of oxalic ac:d ; '■Z'-I parts of crvstallized oxalic acid 

 were necessary; aiid the oxalate of iinie formed weighed 27 grains. From this 

 experiment he draws the coiiclusion which I have staied, (sec A'ni. dt: Chim'.c, 

 lix. 164 ■) But this ingenious chemist does not seem to have been aware of 

 the real composition of oxalaie of lime. 27 grains of that salt are compo.sed 

 very nearly of 10 grains of lime and 17 gr.iins of acid. But the weight of 

 the crystals used by Vauquelin was 22; ihe difference, five, is obviously the 

 water of crystallization in 22 grains ol ihe crystals. Bui iv 22 grains con- 

 tain live of water, it is obvious, that 100 contain very nearly 23. So that 

 his experiment in reality cclncides with mine. 



Bcrgmann 



