20 ' § ^^- REAGENTS. 



I. Potassic sodic carbonate. — KXaCOg. (Carbonate 

 of potassa and soda. KO, NaO, 2 CO^.) — Recrystallize 

 some potassic sodic tartrate, ignite the salt in a silver 

 dish until completely charred, exhaust the black residue 

 with water, filter, evaporate the filtrate to dryness in the 

 silver dish, and keep the salt in a well stoppered bottle ; 

 when it is fused with a little pure sodic nitrate, and the 

 residue is dissolved in water and nitric acid, and then am- 

 monia added, each in slight excess, no flocculent precipi- 

 tate should appear after long standing in a warm place. 



m. Potassic sodic tartrate.— KNaC,H,0„. (Seign- 

 ette salt. Tartrate of potassa and soda. KO, NaO, 

 CgH^O,^.) — This should be recrystallized once or twice. 

 It should give a colorless solution with water. 



n. Potassic Sulpliocyanate.— KCyS. (Sulphocyanide 

 of potassium. KCy S^.) — Dissolve in 20 parts of water. 



26. Quartz, powdered, — SiO„. — Drench red-hot quartz 

 with cold water, and reduce the friable mass to a very 

 fine powder. 



27. a.— Soda lime.— Na.CaO,.— This should not effer- 

 vesce much with acid, and, Mhen mixed with pure sugar 

 and heated to redness, it should evolve no ammonia. 



In order to have the reagent perfectly free from nitro- 

 gen, Lawes and Gilbert found it necessary to mix it 

 intimately with 1-2 "1^ of sugar or some other non- 

 nitrogenous substance, and ignite the mixture in a muffle, 

 then to moisten it, and heat it again gently. 



h. Sodic acetate. — NaC„H302. (Acetate of soda. 

 NaO, CJI^O^.) — This should be colorless and have no 

 empyreumatic odor, and should give no reaction with 

 ammonic molybdate or baric chloride. Dissolve in 10 

 parts of water. 



c. Sodic ammonic phosphate.- NaNHJIPO, Phos- 

 phorus salt. (Phosphate of soda and ammonia. NaO, 



