GLASSFOR many years pharmacists have been "glass conscious" and aware of the necessity of controlling its quality and characteristics when glass containers are used for pharmaceutical preparations. Thus the B.P. 1898 specifies lead-free bottles for solutions of ammonium acetate and citrate and green glass for solution of potassium hydroxide, and in our records are such cases as the extraction of arsenic by potassium carbonate from its glass container and the blackening of suspended bismuth salts by specks of sulphide on the surface of the glass. In recent years, however, we have found it necessary to take an even greater interest in glass because of the gradual introduction of drugs of very high potency, and consequently of small dosage, where regard must be paid to stability, because a small change in structure during a sterilisation process or during storage may mean a considerable drop in potency. Many of these new drugs are sensitive to change of pH and glass can so easily supply the means for this. This more critical attitude was reflected in the B.P. 1932 which, having introduced the modern types of parenteral injections, included control tests for the limit of soluble alkali in the glass containers used and specified those medicaments and preparations which should be packed in provedglass containers. The official tests for the alkalinity of glass were interesting and have led to considerable controversy for there were two schools of thought. Two tests were devised: (a) the crushed glass (or interior) test and (b) the surface test. The crushed glass test was final, for any glass passing that test must also pass the surface test, but not necessarily vice versa. On the other hand it was urged that the surface test was a "practical" test because only the surface came into contact with the medicament. The tests were restricted to containers with capacities of 0-5 ml. to 25 ml. It did not appear logical to apply both tests for only the relatively expensive borosilicate glass would pass both tests whilst the cheaper soft soda-lime glass would rarely pass even the surface test. It is inevitable, of course, that economics should be important and the problem of control of the quality of glass will probably vary in different countries according to the availability of the raw materials. Thus, in Britain borosilicate glass is not in good supply. The problem, however, began to resolve itself by the introduction of the so-called "surfacetreated" soda-lime glass whereby it is possible to produce on its surface a resistant skin of silica which will pass a surface test but not necessarily the "crushed glass'' test. The glass tech'nologists urged the adoption of this surface treated glass for containers, other than ampoules, when an alkali limit was essential. The B.P. 1953 has, in effect, done so; the "crushed" test has been deleted and a surface test retained, but without limitation to the capacity of vessels. 1 feel, however, that this surfacetreated glass has been officially taken on trust for there are no published 1008
Summary A new method for the determination of extinction time data is described. The method has been employed for the disinfection of Bact. coli by aqueous solutions of phenol over a range of concentrations and death times ranging from 2 to over 100 minutes. The use of extensive replication, short sampling intervals, and constant sample volumes withdrawn immediately after inoculation of the bactericide are among the chief features of the technique. Estimates of the mean extinction time obtained from the data are of reproducibility within limits sufficiently close to invalidate other extinction time methods, and are of comparable value with those obtained by the use of any other techniques. The method has been satisfactorily applied to systems containing water‐insoluble phenols solubilised in solutions of soaps (Berry and Bean9) where clumping of the test organisms might completely invalidate other methods of estimation of bactericidal activity.
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