The affix sāti may be used optionally in the sense of cvi when something is changed in all its parts into something else.,
The whole phrase \when the agent has attained to a state it previously had not and the verbs kri, bhu and asti are in conjunction\, is understood here. The affix साति is employed when the original is changed in its totality (कृत्स्न). Thus अग्निसाद् भवति शस्त्रम् \the whole weapon is in a blaze-- has become fire\. We may also say अग्नी भवति शस्त्रम् ॥ So also उदकसाद् भवति लवणम् or उदकी भवति लवणम् \The salt becomes all water\.
Why do we say \in its totality\? Observe एकदेशेन पटः शुक्ली भवति \the cloth whitens in part\.
The word \optionally\ shows that the affix chvi also comes in the same sense. While the optional affixing of these terminations chvi, sati &c is governed by the Maha-vibhasha of sutra 4.1.82 (see 5.3.1.,