The 8:1 is from older work and also uses thiocyanate. These two differences make up for what I said which is based on gold choride and sodium thiosulfate pentahydrate. The ammonium ion also has a fairly substantial effect on the final outcome. This all assumes 100% oxidized gelatin. There are only two sources of this product. One is Kodak and the other is Roussellot. The Formulary sells the Kodak product.