28 VETERINARY HYGIENE 



colour indicates the presence of organic matter. Peat imparts a 

 red-brown colour, iron a reddish tint. Absence of any colour does 

 not imply that the water is necessarily pure. If there is much 

 turbidity the water should be filtered prior to the test being 

 made, and this should be done in every case where the tintometer 

 is used. 



Turbidity. The water should be examined in a white glass 

 flask and compared with distilled water as described for colour 

 detection. The following descriptions are applicable : " brilliant," 

 "bright," "clear," "dull," "slightly opalescent," "markedly 

 opalescent," and " turbid " (Thresh). Estimation of the amount of 

 suspended matter is sometimes a matter of importance, and for this 

 any of the standard works on Water Analysis should be consulted. 



Turbidity in water supplied for potable purposes is always to 

 be regarded with suspicion, as it indicates contamination by surface 

 water. Turbidity following soon after rain is especially objec- 

 tionable. 



Odour. Warm a sample of the water in a flask, cork and shake 

 well. Remove the cork and immediately smell. Note the character 

 of the odour, if any. Descriptive terms are not easy of application 

 as a number of individuals rarely have the same perception of smell. 

 The following have been suggested : Vegetable, aromatic, grassy; 

 fishy, earthy, mouldy, musty, disagreeable, peaty, and sweetish 

 (Thresh). 



Pure water should have no smell. There are, however, two 

 exceptions, peaty water nearly always has a slight odour, and 

 certain waters contain sulphuretted hydrogen. Decomposing water- 

 fauna and flora in service mains are not infrequently the cause 

 of " smelly " water. 



Taste. It is not. often that water to be analysed and examined 

 as to its suitability for drinking purposes is tasted. This may, how- 

 ever, be necessary if complaints as to the water having a peculiar 

 taste are put forward. The senses of taste and smell are often 

 confused. Rain water has a flat insipid taste. Soft waters taste 

 " soft." Ferruginous waters taste of ink. Waters containing 

 much sodium chloride have a brackish taste. Peaty water has a 

 peculiar taste of its own. The water from newly laid mains, 

 especially if these have been laid with pipes the coating of which 

 has not been properly dried, have a tarry flavour. Water treated 

 with bleaching powder tastes of chlorine if the available chlorine 

 used in the water exceeds three or four parts per million. If well 

 aerated after treatment the taste is removed. Hard waters and 

 those containing nitrates and carbonic acid, possibly dangerous 



