Howard T. Graber
1916 Journal of Industrial & Engineering Chemistry  
I n a previous article' entitled "Some Observations upon t h e Assay of Digestive Ferments," I called attention t o t h e great variation in t h e apparent strength of a sample of pepsin due t o t h e age of t h e egg used in t h e test, and showed t h a t eggs between t h e ages of j t o 7 days leave t h e least residue when used in testing t h e strength of t h e pepsin. I therefore recommended, for uniformity in results, t h a t chemists adopt age limits for their eggs when testing pepsin,
more » ... n testing pepsin, and it is interesting t o note t h a t t h e Revision Committee of t h e Pharmacopoeia, having confirmed these findings, have adopted this egg limit in their revised test for pepsin. The revised wording, which I have every reason t o believe will appear in t h e LT. S. P. I X test for pepsin, will state: "Immerse a hen's egg, which should not be less t h a n 5 nor more t h a n 1 2 days old." After having determined t h e large factor which t h e age of t h e egg bears in t h e assay of pepsin, it was of interest t o me t o know how my results would vary when choosing m y eggs as t o age and when going into t h e open market and buying "strictly fresh eggs" from a reliable dealer. I have compiled t h e results from a series of many tests. P a r t of these tests were made with eggs of known age ( 5 t o 1 2 days), a n d t h e balance with socalled "strictly fresh eggs." The pepsin used in all these tests was a sample found t o leave a residue of about I cc. under ideal conditions a n d was chosen because of t h e fact t h a t it is easier t o note slight differences in strength with a residue of I cc. t h a n with a smaller residue.
doi:10.1021/i500010a013 fatcat:pgtgufzay5aovh5gck4yowol64