Sodium sulfate (it is sodium sulfate, the outdated name - "glauberova salt") has chemical formula Na2SO4. Appearance – colourless crystal substance. Sulfate of sodium is widespread in the nature in a look already mentioned the "glauberovy salt" representing compound of this salt with ten molecules of water: Na2SO4x10H2O. Also minerals of other structure meet. Let's say there is a number of hinge plates of the salts similar in appearance, and the task is set: to define what of them – sodium sulfate.
Instruction
1. First of all, remember that sulfate of sodium is the salt formed by the strong basis (NaOH) and strong acid (H2SO4). Therefore its solution has to have rn, close to a neutral indicator (7). Part a small amount of each salt in water and determine by indicators of litmus and phenolphthalein what environment in each test tube. Remember that litmus in acidic environment accepts a red shade, and phenolphthalein becomes crimson in alkaline.
2. Set aside those tests in which color of indicators changed – in them there is definitely no sodium sulfate. Substances, rn solutions of which it is close to neutral, you will subject to high-quality reaction to sulfate ion. In other words, flow a little solution of chloride barium to each test. That test where the dense white deposit was instantly formed, for certain contains this ion because there was such reaction: Ba2 + + SO42-= BaSO4.
3. It is necessary to find out whether contained this substance, besides sulfate ion, also a sodium ion. Can do it was sulfate potassium or sulfate lithium, for example. For this purpose a small amount of the solid relating to this test place in a torch flame. If you see bright yellow coloring - it is for certain a sodium ion. If color is bright red is a lithium, and dark purple – potassium.
4. Follows from everything that signs on which it is possible to distinguish sulfate of sodium are: - neutral reaction of the environment of water solution; - high-quality reaction to sulfate ion (white dense deposit); - yellow coloring of a flame in which solid is brought. When performing conditions it is possible to claim safely is a sulfate of sodium.