Melting range á741ñ: between 188and 189.

Water,Method Iá921ñ: not more than 0.5%.

Residue on ignition á281ñ: not more than 0.1%.

Specific rotation á781ñ: between +3.8and +4.8,determined in a solution of pyridine containing 10mg per mL,with the use of a mercury light at 546.1nm;between +21and +25,determined in a solution of equal parts of chloroform and methanol containing 5mg per mL,with the use of sodium light.

Suitability— Dissolve 10mg each of USP Digitoxin RS,previously dried,USP Digoxin RS,previously dried,and gitoxin,respectively,in separate 5-mLportions of a mixture of 2parts of chloroform and 1part of methanol,and dilute each with additional solvent mixture to 10mL.Then proceed as directed in the Identification testunder Digoxin.The chromatogram of gitoxin shows one fluorescent spot,located between the digoxin and digitoxin spots.

Acid-soluble substances— Boil 1g for 30minutes with 30mLof diluted hydrochloric acid,and filter.Evaporate the filtrate,and dry the residue at 105to constant weight:the residue weighs not more than 5mg (0.5%).

Heavy metals— Boil 2g with a mixture of 25mLeach of diluted nitric acid and water for 5minutes,and filter.Evaporate one-half of the filtrate to dryness,dissolve the residue in 10mLof water to which 3drops of hydrochloric acid have been added,filter if necessary,and add an equal volume of hydrogen sulfide TSto the filtrate:no darkening is produced.

Assay— Dilute about 200mg of the solution,accurately weighed,with 30mLof water.Titrate with 0.1Nsodium hydroxide VS,determining the endpoint potentiometrically.Perform a blank determination and make any necessary correction.Each mLof 0.1Nsodium hydroxide is equivalent to 19.62mg of C6H12O7.Not less than 49.0%is found.

Refractive index á831ñ: between 1.4160and 1.4180at 20.

Specific rotation á781ñ: between +9.9and +11.9,determined as is,at 20.

Add the following:

Assay— Inject an appropriate volume (silanized)into a gas chromatograph (see Chromatography á621ñ)equipped with a flame-ionization detector,helium being used as the carrier gas.The following conditions have been found suitable:a 0.25-mm ×30-m capillary column coated with a 1-µm layer of phase G2.The injection port temperature is maintained at 250;the detector temperature is maintained at 300;the column temperature is maintained at 100and programmed to rise 10per minute to 250.The area of the C2H4O3peak is not less than 98.5%of the total peak area.

Assay— When examined by gas-liquid chromatography,it shows a purity of not less than 98%.The following conditions have been found suitable for assaying it:A3-mm ×1.8-m stainless steel column containing liquid phase G16on 60-to 80-mesh support S1A.Helium is the carrier gas,the injection port temperature is maintained at 180,the column temperature is 200,and the flame-ionization detector is maintained at 280.The retention time is about 8minutes.

Refractive index á831ñ: between 1.5430and 1.5450,at 20.

Melting range á741ñ: between 178and 189.

Chloride content— Dissolve about 400mg,accurately weighed,in 5mLof water.Add 5mLof glacial acetic acid,50mLof methanol,and 1drop of eosin Y TS,and titrate with 0.1Nsilver nitrate VS.Each mLof 0.1Nsilver nitrate is equivalent to 3.545mg of Cl.Not less than 36.1%and not more than 37.1%,calculated on the anhydrous basis,is found.

Residue on ignition(Reagent test): negligible,from 100mg.

Loss on drying á731ñ— Dry it at 105to constant weight:it loses not more than 10.0%of its weight.