IDENTIFYING A MALT FORM A BLENDED WHISKY
First of all, it is important to know that there are two kinds of whisky.
Blended Whisky. A blended whisky is a mix of malts from several different distilleries and grain whisky. The proportion of grain whisky is important to determine the quality of the final product. The advantage of blended whisky is that it's quality is constant over the years guaranteed by the blenders. Lovers of blended whisky use to say that the result is superior to the sum of the composants.
Single Malt Whisky is the direct result of distillation of malted barley. A single malt is produced by one distillery, athough it is possible the bottle contains whisky from different barrels, even from different distillation years. This is done to maintain a certain constance in the taste over the years. Sometimes whisky is sold as "Single Cask", which means that the whisky has matured in the same cask, without mixing casks.
The two kinds of Scotch Whisky - Malt Whisky and Grain Whisky. The Malt Whiskies are divided into four groups according to the geographical location of the distilleries in which they are made, as follows:

(1) Lowland Malt Whiskies, made south of an imaginary line drawn from Dundee in the east to Greenock in the west.

(2) Highland Malt Whiskies, made north of that line.

(3) Speyside Malt Whiskies, from the valley of the River Spey. Although these whiskies come from within the area designated as Highland Malt Whiskies, the concentration of distilleries and the specific climatic conditions produce a whisky of an identifiable character and require a separate classification.

(4) Islay Malt Whiskies, from the island of Islay.

Each group has its own clearly defined characteristics, ranging from the lighter Lowland Malt Whiskies to those distilled on Islay which are generally regarded as the heaviest Malt Whiskies.

Malt Whiskies, which differ considerably in flavour according to the distillery from which they come, have a more pronounced bouquet and flavour than the Grain Whiskies. The production of Grain Whisky is not so influenced by geographical factors and it may be distilled anywhere in Scotland.

WHAT GIVES WHISKY THEIR DISTINCTIVE FLAVOURS

This is one of the mysteries of the industry and a secret which many imitators of Scotch Whisky have tried in vain to discover. Many theories and explanations have been put forward, but there is no universally accepted solution.
Unlike today whisky didn´t get old in centuries past. It was drunk immediately or soon after the production so the spirit must have been rather harsh. Tradition has it that someone found a barrel of whisky that had been left accidentally for a long period, and noticed that the flavour had mellowed, and the whisky attained a pale golden colour thus creating the basis for today´s stringent requirements for an excellent "aquavitae".
The distilling process itself is one factor. Scotch Whisky, after it has been distilled, contains not only ethyl alcohol and water but certain secondary constituents. The exact nature of these is not fully understood, but it is believed they include some of the essential oils from the malted barley and other cereals and substances that derive from the peat. The amount of these secondary constituents retained in the spirit depends upon the shape of the still and the way it is operated and also on the strength at which the spirit is drawn off. Grain Whisky, because of the process by which it is made, contains fewer secondary constituents than Malt Whisky and is accordingly milder in flavour and aroma.

The natural elements of water, peat and the Scottish climate all certainly have a profound effect on the flavour of Scotch Whisky. Water is probably the most important single factor and a source of good, soft water is essential to a distillery. Peat, which is used in the kiln or oven in which the malt is dried, also has an influence that can be detected in the ‘peaty’ or smoky flavour of many Scotch Whiskies.

The Scottish climate is extremely important, particularly when the whisky is maturing. At this stage the soft air permeates the casks and works on the whisky, eliminating harsher constituents to produce a mellow whisky.

Different distilleries produce different flavours of Whisky, the reason for this has always been a very difficult question to answer with certainty on how this should be the case. Most people would agree that the water used is the decisive factor. Adjoining distilleries which draw their water from different sources are known to produce whiskies that are quite dissimilar in flavour. The size and shape of the stills are also important as are the skill and experience of the men who manage them. It is the objective of the distiller to produce a whisky whose flavour and character remain consistent at all times and in all circumstances. This is the true art of distilling, acquired only after many years and often handed down from one generation to the next.