178 STATE BOARD OF AGRICULTURE. 



words, cleaning solution didn't affect the amount of alkali given off during 

 autoclaving. However, in some samples of glassware not treated with 

 cleaning solution before autoclaving, it was impossible to get a pH reading, 

 due to some unknown substance which destroyed the action of the indicator. 

 In these cases new samples of the same glassware were obtained and the 

 experiment repeated several times with the same results. Sets 4a and 4b, 

 table 4; sets 5a and 5b, table 5; set 6b, table 6; and set 4, table 7. In working 

 with buffered solutions as nutrient broth, nutrient gelatin, nutrient agar, etc., 

 the alkali given off from glassware during autoclaving has no appreciable 

 effect on the hydrogen-ion concentration but in less highly buffered solutions 

 it may be sufficient to change the reaction so as to confuse results. Levy 

 and Cullen (5) have found the increase in alkalinity from glass containers and 

 ampules sufficient to decompose aqueous solutions of crystalline strophanthin 

 in the concentration ordinarily emploj^ed in the clinic. 



SUMMARY. 



1. Glassware taken from stock, filled with a non-])uffered solution as 

 conductivity water and autoclaved for 30 minutes at 15 pounds pressure 

 yielded enough alkali to change the reaction of the conductivity water from 

 pH 7.0 to pH 9.8. 



2. The amount of alkali yielded by this same glassware was not sufficient 

 to change the reaction of a buffered solution as nutrient broth. In fact the 

 nutrient broth with a reaction of pH 7.0 before autoclaving had a reaction in 

 some cases of pH 6.8 after autoclaving in this glassware. 



3. Soft glassware yields more alkali upon autoclaving than does hard 

 glassware. 



4. Glassware treated with cleaning solution still gives off alkali after 

 being autoclaved. In some cases the cleaning solution destroyed or neutral- 

 ized substances that interfered with the action of the indicator. 



5. The practice of adding cleaning solution to new glassware before 

 using is recommended. 



6. Laboratory workers should also bear in mind that when working with 

 non-buffered solutions, the alkali yielded by the glassware may be sufficient 

 to change the results considerably. 



REFERENCES. 



(1) Clark, W. M., and Lubs, H. 1916. Hydrogen electrode potential of 



phthalate, phosphate and borate buffer mixtures. Jour. Biol. Chem., 

 Vol. 25, No. 3, pp. 479-510.- 



(2) Clark, W. M., and Lubs, H. 1917. The colorimetric determination 



of hydrogen-ion concentration of bacteriologic culture media. Jour, 

 of Bact., Vol. II, Nos. 1, 2 and 3, pp. 1-34, pp. 109-136, pp. 191-236. 



(3) Cooledge, L. H. 1920. An improved comparator. Jour, of Ind. and 



Eng. Chem., Vol. 12, No. 5, p. 499. 



(4) Foster, Lawrence F. and Randall, Samuel B. 1921. A study of the 



variations in hydrogen-ion concentration of broth media. Jour, of 

 Bact. Vol. VI, No. 2, p. 160. 



(5) Levy, Robert L. and Cullen, Glenn E. 1920. Deterioration of crystal- 



line strophanthin in aqueous solution. Jour, of Expt. Med., Vol. 

 XXXI, No. 3, pp. 267-273. 



[F. W. Fabian.] 



