True amber is sometimes coloured artificially.
Feed the plants artificially as soon as good crops are set; do not wait for signs of distress.
The formula is Fe n, Sn+, where n may vary from 5 to 16; usually it is Fe, S8 or Fe l s S12, the latter being also the composition of the artificially prepared compound.
The ears are usually artificially clipped so as to present a rounded lower margin.
It may therefore be said that caoutchouc has been already artificially or synthetically prepared, and the possibility of producing synthetic rubber cheaply on a commercial scale remains the only problem.