Why is sodium citrate mixture acidic and how to test non-aqueous pH?

[scientifico]

Hello, I've measured the pH of a med containing sodium citrate, potassium citrate and citric acid, why was is slightly acid if sodium citrate is basic ?
How can I measure the pH of a non acquous solution using litmus paper ?
Does some compund is, for example, basic when solid and became acid when put in water ?

thanks

 

[Borek]

Hello, I've measured the pH of a med containing sodium citrate, potassium citrate and citric acid, why was is slightly acid if sodium citrate is basic ?

If it contains citric acid, it can be acidic.

How can I measure the pH of a non acquous solution using litmus paper ?

Technically you can't - pH is a property of aqueous solution.

Does some compund is, for example, basic when solid and became acid when put in water?

Generally speaking solid is usually neither basic nor acidic - it becomes basic or acidic when it dissolves/reacts with water.