Ichthammol
Ichthammol.
Ichthammol [8029-68-3].
»Ichthammol is obtained by the destructive distillation of certain bituminous schists,sulfonation of the distillate,and neutralization of the product with ammonia.Ichthammol yields not less than 2.5percent of ammonia (NH3)and not less than 10.0percent of total sulfur (S).
Packaging and storage—
Preserve in well-closed containers.
Identification—
A:
Dilute 10mLwith 90mLof water,and stir for 5minutes with a magnetic stirrer.Add 25mLof hydrochloric acid,and mix:a heavy,resinous precipitate is formed.Remove the liquid by decantation,and wash the precipitate with 2Nhydrochloric acid until the last washing is nearly colorless.Transfer the precipitate to absorbent paper,allow it to stand for 10minutes,and then transfer 10mg of the precipitate to a 250-mLconical flask.To the flask add 100mLof ether,attach an air condenser to the flask,and stir for 30minutes with a magnetic stirrer:the precipitate does not dissolve completely.
B:
To a solution (1in 10)add 1Nsodium hydroxide,and heat to the boiling point:ammonia is evolved.
Loss on drying á731ñ—
Dry it at 80
for 8hours,and continue the drying at 100for constant weight:it loses not more than 50.0%of its weight.
for 8hours,and continue the drying at 100for constant weight:it loses not more than 50.0%of its weight.
Residue on ignition á281ñ:
not more than 0.5%.
Limit for ammonium sulfate—
Accurately weigh about 1g,transfer to a 100-mLbeaker,and add 25mLof alcohol.Stir,filter,and wash the filter with a mixture of equal volumes of ether and alcohol until the last washing is clear and colorless.Air-dry the filter and residue,and pass 200mLof warm water,slightly acidified with hydrochloric acid,through the residue on the filter.Heat the filtrate to boiling,add barium chloride TSin excess,and heat for 1hour on a steam bath.Collect the precipitate of barium sulfate on a filter,wash it well,dry,and ignite to constant weight.Each g of barium sulfate is equivalent to 566.1mg of (NH4)2SO4.Ichthammol contains not more than 8.0%of ammonium sulfate.
Assay for ammonia—
Dissolve about 5g of Ichthammol,accurately weighed,in 100mLof water,transfer the solution to a distillation flask,add 3g of paraffin,and add 20mLof sodium hydroxide solution (4in 10).Connect the flask to a condenser by means of a spray trap,and immerse the lower outlet tube of the condenser in 30.0mLof 0.5Nsulfuric acid VS.Distill slowly,collect about 50mLof distillate,and then titrate the excess acid with 0.5Nsodium hydroxide VS,using methyl red TSas the indicator.Perform a blank determination,and make any necessary correction.Each mLof 0.5Nsulfuric acid is equivalent to 8.515mg of NH3.
Assay for total sulfur—
Transfer from 500mg to 800mg of Ichthammol,accurately weighed,to a Kjeldahl flask with the aid of 20mLof water.Add 3g of potassium chlorate,then add slowly 30mLof nitric acid,and evaporate the mixture on a hot plate to about 5mL.Cool,repeat the oxidation with 3g of potassium chlorate and 30mLof nitric acid,and evaporate to about 5mL.Add 25mLof hydrochloric acid,and again evaporate to about 5mL.Add 100mLof water,heat to boiling,filter,and wash well.To the hot filtrate add 25mLof barium chloride TS,and heat on a steam bath for 1hour.Collect the barium sulfate on a previously ignited and tared filtering crucible,wash,dry,and ignite,then cool,and weigh.Each g of barium sulfate is equivalent to 137.4mg of S.
Auxiliary Information—
Staff Liaison:Behnam Davani,Ph.D.,MBA,Senior Scientist
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 995
Phone Number:1-301-816-8394