I do a lot of stain work and I would wait three to four weeks if possible to stain after purchase. Keep in a dry, weather proof area if possible-a garage, shed or workshop. If you have to keep the lumber outside, elevate it on some 4 x 4 runners and expose it on clear days.
Scientists say that solutions are homogenous systems. Everything in a solution is evenly spread out and thoroughly mixed. Heterogeneous mixtures have a little more of one thing (higher concentration) in one part of the system when compared to another. Let's compare sugar in water (H 2 O) to sand in water. Sugar dissolves and is spread throughout the glass of water. The sand sinks to the bottom. The sugar-water is a homogenous mixture while the sand-water is a heterogeneous mixture. Both are mixtures, but only the sugar-water can also be called a solution. Pretty much. Solutions can be solids dissolved in liquids.
Mixtures: Homogeneous: a homogeneous mixture is one that appears the same throughout. It is very well mixed. Sea water is a homogeneous mixture of water, table salt and a variety of other compounds, stainless steel is a homogeneous mixture of iron, carbon, nickel and other elements. Heterogeneous: mixtures that are poorly mixed. The substances that are mixed together are easily seen. Example: A banana split is a heterogeneous mixture of ice cream, bananas, whipped cream, nuts, chocolate syrup and other things. The chocolate syrup is a homogeneous mixture of water, cocoa powder, sugar and other compounds. If you look at the syrup it all looks the same.