Keep the solution in small, dark amber-colored, glass-stoppered bottles, carefully protected from dust. Note. When this solution is to be used, fill a burette with it, place the liquid to be tested either for the free iodine it already contains, or for that which it liberates from an excess of potassium iodide added to it, into a flask, and gradually add small portions of the solution from the burette, shaking after each addition, and regulating the flow to drops towards the end of the operation, until the brown color of the iodine has nearly disappeared. Now add a few drops of starch T.S., which will produce a blue color, and then continue to add the hyposulphite solution in drops until the blue tint is exactly discharged. One Cubic Centimeter of Decinormal Sodium Hyposulphite V.S. is the equivalent of : Sodium Hyposulphite (Thiosulphate), Na,S,O,+ 5H20. Iodine, I Chlorine, Cl Iron, Fe, in ferric salts Carefully mix 30 C.c. of pure, concentrated sulphuric acid (of specific gravity 1835) with enough water to make about 1050 C.c., and allow the liquid to cool to about 15° C. (59° F.). Place 10 C.c. of this liquid (which is yet too concentrated) into a flask, add a few drops of phenolphtalein T.S., and afterwards, from a burette, normal potassium hydrate V.S., shaking after each addition, and regulating the flow to drops towards the end of the operation, until the red color produced by its influx no longer disappears on shaking, but is not deeper than pale pink. Note the number of C.c. of potassium hydrate consumed. Then dilute the sulphuric acid solution so that equal volumes of this and of normal potassium hydrate V.S. exactly neutralize each other. EXAMPLE.-Assuming that 10 C.c. of the acid solution first prepared had required exactly 11.2 C.c of normal potassium hydrate V.S., each 10 C.c. of the former must be diluted to 11.2 C.c., or each 1000 C.c. to 1120 C.c. After the liquid is thus diluted, a new trial should be made in the manner above described, in which 50 C.c. of the acid solution should require for neutralization exactly 50 C.c. of potassium hydrate V.S. If necessary, a new adjustment should be made to render the correspondence perfect. Note. It is recommended that, in alkalimetric determinations, when an acid of normal strength is required, normal sulphuric acid be employed, in place of normal oxalic acid V.S. (see note under No. 122). One Cubic Centimeter of Normal Sulphuric Acid is the equivalent of: Sulphuric Acid, absolute, H2SO̟ Ammonia Gas, NH,. Ammonium Carbonate, (NH),CO, Ammonium Carbonate [U. S. P.], NH,HCO NH,NH,CO, Lead Acetate, crystallized, Pb(CHO)2+3H,0 Lead Subacetate, assumed as Pb,(CH3O2)2 Lithium Benzoate, LiC,H,O, (to be ignited) Lithium Carbonate, Li,CO, Lithium Citrate, Li,CH,O, (to be ignited) Potassium Bitartrate, KHC,H,Ö (to be ignited) 6 Potassium Carbonate, anhydrous, K,CO, Potassium Citrate, crystallized, K,CH ̧Ö,+ H2O (to be ignited) Potassium Hydrate, KOH . Potassium and Sodium Tartrate, KNACHO+4H,O (to be ignited) Sodium Acetate, NaC,H,O,+3H,O (to be ignited) Sodium Benzoate, NaC,H,O, (to be ignited) Sodium Bicarbonate, NaHCO, Sodium Borate, crystallized, Ña,B ̧0, +10H,O Sodium Carbonate, anhydrous, Na,CO, Sodium Carbonate, crystallized, Na,CO,+10H,O. Sodium Hydrate, NaŎH Strontium Lactate, Sr(C,H,O,), (to be ignited) The following articles are tested with this solution: 135. Decinormal Sulphuric Acid. H2SO1 = 97.82. 4.891 Gm. in 1 Liter. Dilute 10 C.c. of normal sulphuric acid with enough water to make 100 C.c. One Cubic Centimeter of Decinormal Sulphuric Acid is the equivalent of : Sulphuric Acid, absolute, H2SO.. Combined Alkaloids of Nux Vomica, assumed to consist of equal parts of Gramme. 0.004891 0.0364 0.005599 V. ALKALOIDAL ASSAY BY IMMISCIBLE SOLVENTS. It is a property of many alkaloids that they are soluble in certain liquids in which their salts are insoluble, while in other liquids the case is reversed. When such liquids are not miscible, the conditions are favorable to what has been called the "shakingout" process of separation. In many cases the extraction or separation may be effected by shaking together the concentrated aqueous extract, to which a suitable alkaline precipitant has been added, and some solvent, such as chloroform, ether, benzin, benzol, amyl alcohol, etc. The precipitated alkaloid is thus washed out of the aque ous solution, and is dissolved by the chloroform or other immiscible liquid employed. From the solution of the alkaloid thus obtained, the latter may again be abstracted by a dilute acid. In this Pharmacopoeia the only liquid which is directed as solvent for alkaloids in such assays is chloroform. The extraction is directed to be performed in a glass separator or separatory funnel, which consists of an elongated (globular, cylindrical, or conical) glass vessel, provided with a well-fitting stopper and an outlettube containing a well-ground glass stop-cock. When the solution of an alkaloid, suitably prepared, is introduced into this vessel, and chloroform subsequently added, the latter, owing to its higher specific gravity, will form the lower layer. If the two layers are violently shaken together, there will often result an emulsion, which will separate only slowly, and often imperfectly. This is particularly liable to happen when the aqueous liquid containing the alkaloid either in suspension or in solution is strongly alkaline, and when it has a high specific gravity. To avoid the formation of an emulsion, the extraction should be accomplished rather by rapid rotation and frequent inversion of the separator than by violent shaking. When an emulsion has formed, its separation may be promoted by the addition of more of the solvent, preferably somewhat heated, aided, if necessary, by the external application of a gentle heat (the stopper being removed for the time being), or by the introduction of a small quantity of alcohol or of hot water. The separation of the two layers may also be promoted by stirring the lower, chloroformic layer with a glass rod and detaching from the walls of the separator the adhering drops of emulsion. On withdrawing the chloroform solution of an alkaloid from the separator, a small amount of the solution will generally be retained in the outlet-tube by capillary attraction. If this were lost, the results of the assay would be seriously vitiated. To avoid this loss, several successive, small portions of chloroform should be poured into the separator without agitation, and drawn off through the stop-cock to wash out the outlet-tube. Another source of loss is the pressure sometimes generated in the separator by the rise of temperature caused when an alkaline and an acid liquid are shaken together. On loosening the stopper, the liquid which adheres to the juncture of the latter with the neck is liable to be ejected. This is best avoided by mixing the liquids at first by rotation (avoiding contact of the contents with the stopper), and allowing them to become cold before stoppering the separator. 1 To be determined to at least two decimals by titrating the uncombined acid with centinormal potassium hydrate V.S., The same precautions should be observed when an alkali carbonate has been used, in place of a caustic alkali, for setting free the alkaloid. In this case the liquids should be cautiously and gradually mixed by rotation, and the separator should be left unstoppered until gas is no longer given off. If a regular glass separator is not available, an ordinary burette, stoppered with a sound cork, may be employed in its place. In this case the quantities of the alkaloidal solution and of the volatile solvent must be adjusted to the size of the burette. QUESTIONS ON CHAPTER LXII. PHARMACEUTICAL TESTING. What is meant by synthesis? What is meant by analysis? Upon what are the principles of analysis based? What are meant by reagents and test-solutions? What two kinds of analysis are in use? What is meant by qualitative analysis? What is meant by quantitative analysis? What two kinds of quantitative analysis are in use, and what is the difference between them? What is the legitimate and proper meaning of a normal solution? What are decinormal and centinormal solutions? In what other ways has the term normal solution been applied? What is meant by proximate analysis? What is meant by ultimate analysis? What system is used by the U. S. Pharmacopoeia in analytical operations requiring definite weights or measures? What is the use of graduated flasks? What is the use of graduated jars? What is a burette, and how is it used? For test-solutions that are decomposed by organic substances, can a rubber tube be used? What can be used in its place? What is Erdmann's float? What is its use? How may pipettes sometimes be used instead of burettes? PART V. MAGISTRAL PHARMACY.' UNDER the head of Magistral or Extemporaneous Pharmacy will be considered the preparation and dispensing of medicines intended to meet the occasion and which are to be compounded at once. The subject of official or galenical pharmacy has been considered in the previous pages, the distinction being that in the latter the preparations are intended to be permanent, and are generally made in advance and kept on hand ready for use, whilst those which are magistral are mostly intended to last during the occasion which calls them into existence. There are several classes of official medicines in which permanent and extemporaneous preparations are both embraced: it has been deemed most practical to consider such under the above head. Examples are found in plasters, powders, ointments, etc. Some of these are generally kept on hand ready for use. If they are not called for soon, they become stale or deteriorated, and experience soon demonstrates that the best plan is rapidly to improve the apparatus and facilities of the store to the highest point, so that all extemporaneous preparations may be quickly and skilfully compounded on call, and thus a reputation is soon acquired for always dispensing those which are fresh. For this reason, most ointments should not be made in larger quantities than are necessary to supply the demand of the moment. Magistral Pharmacy is unquestionably the most important division of the whole subject. It embraces the principal amount of the labor in the store, and calls for the exercise of more tact, knowledge, and ability than any other branch. Owing to the fact that the ability to practise extemporaneous pharmacy successfully depends largely upon the personal qualities of the pharmacist, very little can be written upon the subject which would be generally useful. Good training under the watchful eye of a skilled preceptor and practical experience will alone give the confidence and knowledge of details that assure success. All that will be attempted under this head will be to collect and arrange such points as the author has found useful in his own experience, in the hope that at least some of them may be of service to others. A chapter on the arrangement of the store, with a description of the facilities for practising extemporaneous pharmacy, will properly introduce the subject. 1 The word magistral is derived from magister, a master, and is defined as "a term applied to medicines prescribed for the occasion, by a competent person, in distinction from such as are official, or kept prepared in the shops. As the latter are prepared according to a certain formula, an intelligent apprentice is generally equal to the task; but the knowledge of a master is needed to give directions for an original preparation."-Thomas. |