February 17, 1969
Editor, Merck, Sharpe and Dohtne
Research Laboratories
West Point, Penna. 19486
Dear Dr. Lyght:
During recent years I have had occasion to read the Merck Manual, 11th Edition, and I have made note of some points that may be worth mentioning to you.
I shall write now only about the section Special Baths, beginning on page 1690.
Item 6 is on Sulfur Baths, which are said to have a mild fungistatic and keroatolytic effect.
From the description it is clear that a sulfur bath contains the sulfide ion or hydrosulfide sion. One way of making a sulfur bath is said to be to add five or ten teaspoons of zinc sulfate to a tub two thirds filled with water.
This statement is, of course, not true. A solution of zinc sulfate does not contain any sulfide ion or hydrosulfide ion, and it would not undergo any reaction to produce these ions. This solution is, moreover, not fungistatic and keroatolytic; it is, instead, astringent. The other solutions mentioned, of sodium sulfide and calcium sulfide, are alkaline; a solution of zinc sulfate is acidic.
There is no compound of zinc that can give a sulfur bath. Zinc sulfide is insoluble, and any solution of zinc and sulfide would react to produce this insoluble sulfide.
I judge that reference to zinc sulfate in this section was made by error. Perhaps you intended to describe an astringent bath—an acidic bath made by adding sine sulfate to water.
I note also that the name Sulfurated Lime Solution is used for calcium sulfide solution. The Merck Index, 7th edition, page 198, mentions that calcium sulfide is erroneously called "Sulfurated Lime". Probably the correct name should be given in the Merck Manual.
Sincerely yours,
Linus Pauling
LP:jj
February
17, 1969
