312 MURIATIC ACID GAS. [BOOK ir. 



edges, dry and discoloured ; and, though it was then removed 

 into the air, they gradually shrivelled and died. Like the 

 sulphurous acid, the hydrochloric acid gas acts thus inju- 

 riously in a proportion which is not perceptible to the smell. 

 Even a thousandth part of hydrochloric acid gas is not dis- 

 tinctly perceptible ; a ten-thousandth made no impression on 

 the nostrils whatever, although great care was taken to dry 

 thoroughly the vessels used in making the mixtures. 



This, however, by no means agrees with the observations of 

 others, which go to show that although muriatic acid in excess 

 is, like all other acrid fluids, destructive of vegetation, yet in 

 minute doses it may be beneficial. This was shown some 

 years since by experiments tried in the Garden of the Horti- 

 cultural Society. Mr. Fortune found that when plants were 

 placed in a confined situation, and exposed to the fumes of 

 weak muriatic acid, so far were they from suffering in conse- 

 quence, that they grew with augmented vigour ; and when half 

 killed by exposure to deleterious influences, they rapidly 

 recovered by being brought in contact with this vapour. 



Mr. Solly has found that not only is the vapour of muriatic 

 acid inoffensive in moderate quantity, but that no action of 

 an unfavourable kind is produced upon plants even by large 

 quantities applied to the roots. Upon this singular fact we 

 must quote his words : 



" Two perfectly similar plants of the Hydrangea were taken 

 and placed under the same general conditions with respect to 

 light, air, &c., and watered with dilute solutions, the one of 

 carbonate of soda, the other of muriatic acid, commencing 

 with very small quantities and gradually increasing the doses. 

 At the beginning of the experiment it was difficult to distin- 

 guish the one from the other; they had both the same 

 number of leaves, were nearly of the same size, and alike in 

 colour and general vigour, being both remarkably healthy 

 plants. The solutions taken consisted of one drachm of con- 

 centrated muriatic acid, and one drachm of carbonate of soda, 

 each dissolved in fifty drachms of water ; of these at first one 

 drachm diluted with two ounces of water was given to each 

 plant daily, but the dose was gradually increased to twelve 

 drachms of each solution, so that in a month the one had 



