Assertion: nitrous acid | /r/HasProperty | necessary to start the reaction
Facets:
value: in all cases
type: TEMPORAL
Source sentences:
text: While Veley agrees that the metals copper, silver, mercury, and bismuth differ in their action from the rest of the metals, yet he maintains that in all cases nitrous acid is necessary to start the reaction, and that nitrous acid is the primary product in all cases.