Does lactose monohydrate convert to lactose after drying?

[chemist23]

If I dry lactose monohydrate at 60°C for 12 hours, will it become just lactose?

I am trying to determine if I should use the molecular weight of lactose monohydrate or lactose when performing calculations when using the dried standard.

Also does this apply to all monohydrates after drying?

[DR]

My educated guess is "no" but I suggest using a balance to be sure.

PS - don't be too surprised if your lactose is a darker shade of off-white after drying.

[Don_Hilton]

I would suggest a little research on drying lactose. A quick look at google brought me to this interesting link: https://www.google.com/url?sa=t&rct=j&q ... CDEY6Pqwo1. (Long story short - after 12 hours at 60 degrees, you should still have the monohydrate. Also the water content depends on the ratio of alpha to beta lactose present - and you have not indicated the source of the lactose. Depending, on your lactose source and the precision and accuracy you need, lactose may be a tricky compound to use as a primary standard.