Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/891

 p H T P H T 855 PHTHALIC ACID. This name was given by Laurent to a di-basic acid, C 8 H 6 O 4, which he obtained by the oxida tion of naphthalin or its tetra-chloride with nitric acid. Schunck subsequently obtained the same acid by boiling alizarin with nitric acid, but failed to recognize its iden tity with Laurent s. One part of naphthalin is mixed with two parts of chlorate of potash, and the mixture added cautiously to ten parts of crude muriatic acid. The product, C 10 H 8. C1 4, is washed with water and then with &quot; ligroin &quot; (the more volatile fraction of petroleum). The chloride thus purified is oxidized by boiling it with ten parts of (gradually added) nitric acid of 1 45 specific gravity, evaporated to dryness, and the residue distilled to obtain the anhydride C 8 H 4 3, or PO rationally C 6 H 4 pQ&amp;gt;0, long colourless needles fusing at 128 0., the boiling point being 276. When boiled with water it becomes (~ OOTT phthalic acid, rat. formula C 6 H 4 QQQjj, rhombic crystals, fusing at 184 C. with transformation into anhydride, very slightly soluble in water (100 parts at 11 dissolve 077 parts), more soluble in alcohol (100 of absolute dissolve 10 1 parts at 15). Phthalic acid, when heated to redness with lime, breaks up into C0 2 and benzol ; the lime salt when mixed with one equivalent caOH of lime, and kept at 330 to 350 C., yields carbonate and benzoate CeH^oOct + cdOH = CaC 3 + C 6 H 5 COOca (Ca = 2ca - 40). Hence phthalic acid should be obtainable by the oxidation of di-derivatives, C 6 H 4 R R&quot;, of benzol (R = CH 3, C 2 H 5 , &c. ), and indeed two acids, C 6 H 4 (COOH) 2, can be thus produced, but neither is identical with phthalic. Tercphthalic acid is obtained by the oxidation of ordinary cymol, O TT pC 6 H 4 pTT 7 , or other similar &quot;para&quot; bodies with bichromate of potash and sulphuric acid. It is a white powder, quite insoluble in water, sublimable without fusion or dehydration. Isophthalic acid is obtained similarly from &quot; meta &quot; derivatives, C 6 H 4 R 2 , of benzol, hair -fine needles fusing above 300, almost insoluble in water, but pretty easily soluble in alcohol. Ortho-bi-derivatives of benzol ought to give &quot; ortho,&quot; i.e., Laurent s phthalic acid ; but this acid itself is oxidized by the bichrome mixture into C0 2 and H 2 0. Plithaleins are a most interesting family of coloured derivatives of phthalic anhydride, which were discovered by Baeyer, and soon found their way into the colour industry. As an example we quote phenol-phthalein, obtained by the union of the anhydride with phenol, C 6 H 5 OH = H + C 6 H 4. OH = H + &quot; Phen. &quot; The phthalein is P TI CO p. U U4 C(Phen) a &amp;gt;U Phthalic rest. and, as will easily be understood, something widely different from the di-phenyl-phthalic ether. Phthalic anhydride and resorcin one of the three di-hydroxyl derivatives, C 6 H 4 (OH) 2, of benzol unite into &quot;fluorescin,&quot; distinguished by the strong fluorescence of its solutions. Tetra-brom-fluorescin, a beautiful red colour, is used industrially as eosin (from Greek i^j, the morning-red). PHTHISIS (&amp;lt;0m) or CONSUMPTION. This term, al though applicable to several forms of wasting disease, is commonly used to designate a malady having for its chief manifestations progressive emaciation of the body and loss of strength, occurring in connexion with morbid changes in the lungs and in other organs. Few diseases possess such sad interest for humanity as consumption, both on account of its widespread prevalence and its destructive effects, particularly among the young ; and in every age of medicine the subject has formed a fertile field for inquiry as to its nature, its cause, and its treatment. On all these points medical opinion has under gone numerous changes with the advance of science and the application of more accurate methods of investigation; yet, notwithstanding the many important facts which within recent years have been brought to light, it must be admitted that our knowledge of this disease is still far from complete. As regards the nature or pathology of consumption it is unnecessary in a notice like the present to refer at length to the doctrines which have from time to time been held upon the subject, further than merely to indicate in a general way the views which have been more or less widely accepted in recent times. In the early part of the present century the study of the diseases of the chest received a great impetus from the labours of Laennec, whose discovery of the stethoscope led to greater minute ness and accuracy in investigation (see AUSCULTATION). This physician held that phthisis depended on the develop ment of tubercles in the lungs, which, undergoing various retrograde changes, led to the breaking down and excava tion of these organs, in short, produced the whole pheno mena of consumption ; and, further, that this tuberculous formation affected various other parts and organs, and was the result of a morbid constitutional condition or diathesis. This doctrine, which was generally taught during the first half of the century, and even longer, was to some extent superseded by that to which the greatest prominence was given by Niemeyer and others, namely, that the majority of cases of phthisis had their origin in an inflammation of the lung (catarrhal pneumonia), but that tubercle the existence of which was freely admitted might occasionally be evolved out of this condition. This view has had wide acceptance, but has been modified in a variety of ways, especially by its extension to inflammation in other parts besides the lungs, the unabsorbed products of which are held to be capable of producing tubercle by infection from within the system. Still more recently there has arisen another doctrine in connexion with the discovery by Koch of the micro-organism or bacillus of tubercle, which can be cultivated and which, when inoculated, appears capable of producing tubercular disease, namely, the doctrine of the infectiveness of phthisis by means of this &quot; microbe &quot; received into the system from without. This view, which is supported by many striking facts and arguments, has been extensively adopted as furnishing in all probability a rational basis of the pathology of tubercular consumption. Yet it has not been universally accepted, being held by many to be insufficient to account for the origin and course of the disease in numerous instances and in certain of its forms. It is impossible to deny an important place in the course of the disease to inflammatory processes. Even in those cases where the lungs are infiltrated with tuber cular deposit evidence of inflammation is abundantly pre sent, while, on the other hand, it would seem that in not a few instances the process is inflammatory throughout. That phthisis, therefore, is not the same process in all cases, but that there are distinct varieties of the disease, is made clear by the morbid anatomy of the lungs no less than by other considerations. Whatever be the form, the common result of the presence of these disease-products is to produce consolidations in the affected portions of the lungs, which, undergoing retrograde changes (caseation), break down and form cavities, the result being the destruction in greater or less amount of lung-substance. These changes most commonly take place at the apex of one lung, but with the advance of the disease they tend to spread throughout its whole extent and to involve the other lung as well. When the disease is confined to a limited area of a lung it may undergo arrest even although it has advanced so far as to destroy a portion of the pulmonary tissue, and a healing process may set in and the affected part cicatrize. This is, how ever, exceptional, the far more common course being the progress of the destructive change either by the spread of the inflammatory process or by infection through the lymphatics, &c., from the existing foci of diseased lung- tissue. Various morbid changes affecting the lungs them selves or other organs frequently arise in the course of phthisis, complicating its progress and reducing the chance of recovery. Of these the more common are affections of the pleura, stomach, liver, kidneys, and especially the in testines, which in the later stage of the disease become ulcerated, giving rise to the diarrhoea which is so frequent and fatal a symptom at this period.