low (Figure 1B), then violet (Figure 1C), and eventually grayish
(Figure 1D), after which the colloid breaks down and particles
settle out. Similar aggregation may also occur if the
reaction is interrupted before all of the silver salt has been
added.
It was also found that the initial concentration of sodium
borohydride must be twice that of silver nitrate:
[NaBH4][AgNO3] = 2.0. When [NaBH4] was varied from
2.0 mM while using 1.0 mM [AgNO3], breakdown of the
product took place in less than an hour (Table 1).