Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall.

Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    46/970
    but to sewage or manure matter specially;' and they state, 'this seems to he an inference which can hardly be accepted. It would be perfectly correct if aU the nitrogenised matter supplied to the Thames or other waters was after conversion into nitrites and nitrates retained in the water, and if also all those salts could be referred to sewage and manure matter only. But such is not the case. 'All the analyses, they say,' show how variable the quantity of those salts is in diflerent parts of the river's com-se, and that the quantity present at any place is not so much dependent upon the sewage received as the removal which has been effected by vegetation and other causes, by the inter- ference of the tributaries, and by the addition from springs; so that, even supposing them to originate solely from ammal matter, the residue affords no comparative results as to the amount of the ongmal con- tamination. The interfering causes are too numerous to allow us to assign any value to the remainder.' These strictures of the Commissioners are to a certain extent correct- there is no doubt but that nitrous and nitnc acids m water are formed from the decomposition of almost .l^^^d of orgamc matter, though in sewage-polluted rivers they are doubtless krg% derived from sewage, and animal nitrogenous matter; also that th^ acids once formed disappear fi-om water fi'om the «a?«e«^!^«,°t Xt by the Commissioners. What then we have to bear m mmd is tiiat the ^idB in question take their origin m mtrogenous orffamc mcOt^ of some kind or other, not exclusively ^^wage ; and next that the iiterfering causes' are causes of decrease, so that the quantities ot nitrous a?d nitric acids actually found represent usually far less than Hhe previous organic contamination.' fo get at an approximation of the^ organic poUution of water, at least three things must deter- mined: the ft-ee ammonia, the nitrous and nitnc acids, and the ^n^fcomi^Sr^^^^^^ that the sources, such as springs and weUs, most fi-ee from possible contammation, show the iLef skeletons, that is to say, the largest amount of nitac acid, and, Say be remarked, the smallest amount of undecomposed -tirognous matter. This, of course, it is unportant to bear m m nd: but stiU the S remains, that the nitric acid of springs and wells, however deep, of cS iSlf, and of soils, owes its%xistence to oxidised organic mattS and that the quantity found does really represent a certam Tantity of that organic matt'er. The water of deep weUs makes ite laT nto those welb from the surface, c^^J'^^f/^^^ 3me matter, which, for the most pari, ere it reaches these wells, has become 'Tltit'cmf t?f to remark that in most analyses the oxidized or Jnic matter Ts put down as niti-ic acid, and no attempt is made to SrminTwhethe? the acid reaUy exists in that form or as niti-ous S Now this is really a distinction of great practical importance,