§ 141. WATER. 271 



substance obtained in 5, and digest the mixture in a flask, 

 15 minutes at a boiling heat, filter, and repeat the same 

 operation twice with the residue. Evaporate this aque- 

 ous extract to dryness on the water-bath, with the addi- 

 tion of a few drops of acetic acid, extract the residue 

 with strong alcohol, filter the liquid, evaporate the filtrate 

 until the alcohol is expelled, and dissolve the residue in 

 distilled water; by this treatment pectose is removed 

 from the aqueous extract. Determine tannic acid in the 

 solution finally obtained (§ 77). 



CHAPTER X. 

 BEVERAGES. 



I. 



WATER. 



141. For a complete analysis of water, we must refer 

 to Fresenius's Quantitative Analysis for directions, while 

 we confine ourselves here to such special determinations 

 as possess a more direct domestic or agricultural interest. 



a. Total Dry Substance in Solution.— Evaporate 500 

 grms. of the water to dryness, in a platinum dish, at a 

 temperature at all times below boiling ; dry the residue 

 at 130° C, and weigh it; ignite it, moisten the residue two 

 or three times with a concentrated solution of ammonic 

 carbonate, drying it each time cautiously ; finally ignite 

 the residue gently, and weigh the total non-volatile dry 

 substance. 



Or, instead of treatment with ammonic carbonate, dis- 

 solve the ignited residue in water in the crucible, pass a 



