"No, I ain't" said the seedy one, sniffing again. "But I don't like your talk. You and me have been friends, off and on, for fifteen year; and I never yet knew or heard of you giving anybody up to the law--not no one. And here was a man whose saleratus you had et and at whose table you had played games of cards--if casino can be so called. And yet you inform him to the law and take money for it. It never was like you, I say."

An old name for baking powder.

Source: Webster's Revised Unabridged Dictionary (1913)

Saleratus \Sal`e*ra"tus\, n. [NL. sal a["e]ratus; -- so called
because it is a source of fixed air (carbon dioxide). See
Sal, and and A["e]rated.] (Old Chem.)
A["e]rated salt; a white crystalline substance having an
alkaline taste and reaction, consisting of sodium bicarbonate
(see under Sodium.) It is largely used in cooking, with
sour milk (lactic acid) or cream of tartar as a substitute
for yeast. It is also an ingredient of most baking powders,
and is used in the preparation of effervescing drinks.

baking powder was a 'new invention'-- corn (maize) has no gluten, so you can't use Yeast effectively to make it rise (no matter the colonalist tried and tried to do so!) american indians had long use 'wood ashes' mixed with the corn, to make a leavening.. this did work--and out of this technology grew baking powder.. (today most baking powders are combo of consisting of sodium bicarbonate and cream of tartar.)