I have a jug of apple cider in the fridge that has semi frozen ie.turned into a liquid/slush

but nothing other than it has frozen! is there some odd attribute about apple cider that would explain this phenomenon?

Sometimes, part of your fridge will reach below freezing. Nothing to do with the cider.

Sometimes, part of your fridge will reach below freezing. Nothing to do with the cider.

but wouldn't the other stuff freeze too?

I suspect the cider was touching the back wall of your fridge unlike the rest of the stuff which is typically colder.

Ethanol (alcohol) will lower the melting point. Instead of 0 degrees C, it will only freeze at -4 degrees C or something.

Here's a table of the freezing point of water/ethanol mixtures.

 

Another important question is:

What other items did you have in the fridge?

 

Try to put the jug of cidre in another spot in the fridge, and see if it turns to a liquid again.

Applejack (ie, concentrated hard cider) is made by fermenting the cider and then letting it partially freeze. Freezing separates the alcohol from water due to differences in their freezing points (–114°C versus 0°C), as compared to distilling, which separates the alcohol from water due to differences in their boiling points (78°C versus 100°C).

 

Water will freeze at a much higher temperature than alcohol (ie, it'll "freeze first" as the mixture cools), and it will do so from the outside in, so you'll see ice (mostly frozen water with a little alcohol) around the edges of the container with a mixture in the center of a higher alcoholic content. Interestingly, as the water freezes out of the mixture, the alcoholic content of the remaining mixture increases, and so, lowers its freezing point. The remaining mixture can be poured off (or the ice removed), and the process repeated.

 

Hard cider has an alcoholic concentration similar to beer or wine, but applejack can have a higher concentration similar to brandy (ie, distilled wine).

Refrigerators are imperfect devices, the less ideally they are designed the higher the tendancy for cold and warm spots. This tendancy is increased when the refrigerator is overfilled so that air cannot freely circulate, frequently opened, have large amounts of warm items put in it at once or if there is a leaking seal. Side by side refrigerators include a fan to circulate cold air from the freezer into the refrigerator and back. The controller and or fan may be malfunctioning as well.

Ethanol (alcohol) will lower the melting point. Instead of 0 degrees C, it will only freeze at -4 degrees C or something.

Here's a table of the freezing point of water/ethanol mixtures.

 

Another important question is:

What other items did you have in the fridge?

 

Try to put the jug of cidre in another spot in the fridge, and see if it turns to a liquid again.

everyday stuff milk, pop, watter etc. and it was in the middle and not near the back at all