Syrup of Salt of Steel.
Take Succory-water 8 ounces; Salt of Steel powdered 2 drams; melt it thoroughly over the Fire in a glaz'd Vessel, then set it by two days, that its Crocus may be precipitated; which done, decant the pure clear Liquor, and adding fine Sugar8 ounces, Oil of Cinnamon and Nutmeg each 2 drops: Make a Syrup.
If you pout the solution of Salt of Steel into Milk, 'twill not coagulate it at all; therefore that Salt, tho'prepar'd out of Oil of Vitriol, (one of the most Acid of Acids) yet contains no Acid in it; which is remarkable enough.
Where I had this Note I cannot call to mind; but I believe its partly a mistake, and I wish I knew all mine, that I might retract 'em. Others Experiments are not always to be rely'd on. My own was as follows.
I put into three earthen Porrengers, cold, tepid, and boiling hot Milk, and poured in to each the Solution; and after having let them stand by 24 hours, found the cold scarce turned at all, the tepid a little, but the hot Milk was perfectly separated into a thin bluish Serum, and a coagulum swimming over it; which yet was rather a thick Cream than a true Curd.
Thomas Fuller
Pharmacopeia Extemporanea 1710