There's just one problem with participating in a whisky tasting, sampling some of Scotland's best whiskies as if they were fine wines – whisky is powerful stuff. It is magical, and it is lethal. If you drink neat vodka you know you are dicing with the drink devil, but to savour a single malt is to be lulled by honeyed, dulcet, earthy flavours that warm the cockles of your heart even as the alcohol does its work. This is one of the most aesthetically pleasing ways you can possibly get drunk, which makes it one of the demon's dirtiest tricks.

If you are going to be tempted by the 40% devil, the Gilbert Scott bar at London's St Pancras hotel is a fine gothic location, its pointy perpendicular windows, rich Venetian gilding and lofty Victorian vaults offering the kind of place where someone might fall prey to his inner dark side in a story by Robert Louis Stevenson. I am here for a master class in whisky connoisseurship, to prepare for Burns Night, on 25 January, when Scots and lovers of Scotland all over the world will be drinking the national drink and eating haggis in celebration of Robert Burns. But my favourite Scottish writer has always been Stevenson and as whisky expert Cory Soutar pours out different shades of translucent wood-coloured liquids, I can't help thinking of the potions of Dr Jekyll. Am I about to become Mr Hyde?

It is no coincidence whisky is the colour of wood because it is coloured, and flavoured, by the stuff. Preferably oak. Soutar has with him a bottle of pure white spirit, a sample of raw distilled whisky before it has been aged in oak. We sip the fruity, 64% proof chemical. It is far nicer that some commercially sold liquors I have tasted. It goes down easier than grappa, for instance.

Scottish whisky, Soutar explains, is made from barley that is roasted (malted), mashed, brewed and distilled to produce this white liquor. The best whiskies are single malts, made from one source of barley at a single distillery. Then the subtle part begins: the result is aged in oak, in the case of the best whiskies for 10, 18 or 30 years.

I sip (I say sip but, after the raw distillate, things are warming up at this table of drink science) my favourite single malt, a 10-year-old Ardbeg from the island of Islay. The terrain of Islay is sodden with peat and Ardbeg tastes of this richly decayed vegetable matter. It is at once pure – all the good single malts have this crisp watery purity that sets off their other flavours – and memorable, like drinking smoked salmon.

It is pure chance that I happen to know it so well. I once went to interview the artist Douglas Gordon in Glasgow and turned up just as he was absorbing some private bad news. To get through the interview he opened a bottle of this amazing stuff, which we polished off. If I purchase whisky, it is always Ardbeg.

Soutar tries to change that. We move on to Glenmorangie's Original. If Ardbeg is a cheese-ripe burgundy, then Original is a classy claret – it has a cleaner taste that many people might prefer (and it's half the price of Ardbeg). I love its crystalline golden simplicity – no wonder it is the bestselling whisky in Scotland. Incidentally, the shades of whisky colour are marks of age and therefore richness: the longer it spends in oak, the browner it gets. Glenmorangie re-uses American bourbon casks for shades of flavour, then finishes its speciality whiskies in sherry vats or Tuscan wine barrels. The latter variety, Artein, combines the tastes of chianti and scotch, which sounds disgusting, but is refined and delicious.

A tough job, but someone's got to do it: some of the whiskies Jonathan Jones sampled. Photograph: Sarah Lee for the Guardian

The truth is that all single malts are delicious, in different ways. I try another 10-year-old, this time Glenfiddich, whose deep, manly firmness immediately makes you feel you are playing golf at Gleneagles or fly fishing on the Tay. That might be too manly for me so I switch to Oban, again wondrously pure but very different in its mix of flavours: mellow, inward, one to muse over in your library, perchance.

My only disappointment is Monkey Shoulder, a top blended whisky. Blends of various malts are what most of us mean when we say whisky, but in comparison with a single malt, even the best blend seems rough. Two sips and I feel a bit nauseous. Back to the pure, peaty Ardbeg for me.

By this stage things are getting ridiculous. I have learned as much as I can with a semblance of dignity. I may not be turning into Mr Hyde but I have definitely entered into the realm of the intoxicated. The drink devil is grinning as he gets ready for Burns Night.