S48 • Examination of the Red coloured JVatcr 



they at length are converted into a sort of sHme. The 

 colouring matter combined with the albumen undergoes 

 also essential changes, till, being gradually overloaded with" 

 oxygen, it is entirely decomposed. When left to itself ni 

 stagnant water this disappearance of the colouring matter, 

 takes place only very slowly. The coloration of the water 

 by it may therefore, especially in winter, continue several 

 weeks. On the other hand, when c^ speedier saturation 

 with oxygen is eflccted the colour is immediately decom- 

 posed, as is the case m hea the coloured water is decom- 

 posed by nitrous acid or oxygenated muriatic acid. 



Nothing further, therefore, seems necessary to explain 

 this phtenomeaon than a botanical determination of those 

 plants which after their death transmit these component 

 parts to water. This task, however, I must leave to 

 botanists who may have an opportunity of making such 

 researches on the spot. ■ But I must here observe, that a 

 season of the year in which one can hope to find these 

 plants in their living state ought to be chosen for this^ 

 purpose. 



From various grounds, however, it appears to me pro- 

 bable that these plants belong to the order of the crypto- 

 g;amia aquatic plants, and are peihaps of the species of the 

 Conferva tremdla, Lira, &c. Albumen seems to form a 

 principal component part in these plants, because on their 

 decomposition in the dry way, besides the usual products, 

 Ihey give also ammonia. It might therefore be of import- 

 ance to examitie whether this colouring matter, which ma- 

 nifests itself by the natural decomposition of the plant, 

 could be extracted from it imuicdiately by artificial means. 

 I am inclined to t^iink that this matter will be found in the 

 Ulva priwiformis, Linn., because this singidar plant, at 

 the end of its vegetable life, is converted into a s:elatinou3 

 substance, and in that state, before its total solutron, floats 

 for some time on the surface of the water. The phasno- 

 mena I observed in ray experiments on this coloured water 

 exhibited a chemical analogy to those of the colouring 

 matter obtained from the indigo plant, Indigofera iiiwto- 

 riu; LhL argent io:; Lid. dispcrma'; and from woad, Isati^ 

 twetoriu. For though the water appeared of a dark red 

 crnnson colour, this colour was merely an optical illusion, 

 occasioned by the refraction of the ravs of light. The real 

 <'olour was a pur: blue. This propcriv of in'Sioo matter to 

 assume an apparent red colour I have obsei-ved in the 

 solid colouring matter itself, as the best sort of the West 

 indian ia::ig;o, as w-eil as that extracted from woad, ex- 



• ^J^ibits 



