Establishing secure connection
It happens in chemistry too.  In his book <i>The Green Flame</i>, Dequasie told the following story:<p>"The salesman had been selling hydrochloric acid, sometimes known as muriatic acid. The industrial grade usually had a green tint caused by contamination with iron.  The company that the salesman worked for improved its equipment at considerable expense and proudly began putting out water-white muriatic acid.  The salesman immediately began getting complaints from customers who did not want that weak white stuff.  They insisted that they wanted that strong green stuff that they used to get.  So, for those customers, the salesman arranged to have a small nail dissolved in each jug shipped to them.  Result: happiness."