40 



■ ponere nentrale Carbonater maa blive at tilskrive gradvise 

 Omsætninger mellem tie i Søvandet existerende kulsure 

 Salte og Magnesiaforbindelserne, og de. af Dr. Jacobsen 

 hos Søvandet iagttagne Egenskaber maa derfor ogsaa i 

 niere eller mindre Grad tilligge alle andre magnesiaboldige 

 Mineralvande. eller naar man Legger Roses ovenciterede 

 TJdtalelser til Grund, alle Saltopløsninger, lorsaavidt de 

 foruden Alkalier og Jorda lkalier tillige indebolder opløse- 

 lige Salte af nogen af de svagere Baser, som meil Kulsyren 

 danner ubestandige Forbindelser. Denne Onistændighed 

 vil saaledes uden videre stemple saa godt som alle de til 

 Bestemmelse af Forholdet mellem den frie og bundne Kul- 

 s\ ic i Mineralvande anvendte talrige Methoder som mere 

 og mindre upaalidelige ljgeoverfor magnesiahqldigé Mine- 

 ralvande, idet man ved dem til Bestemmelse af. neutral- 

 bunden Kulsyre enten anvender Residuet fra Iriddampning 

 eller paa anden Maade benytter sig af Kogning, hvor den 

 eiter det forhen udviklede vil være utilladelig. 



Det vil sluttelig ikke være paa urette Sted kortelig 

 at berøre de Synsmaader, som fra aldre Tider har været 

 gjort gjældende, hvad angaar de i Sovandet indeholdte 

 Carbonater. 



Eiter .de Fremgangsmaader. hvorved disse af aldre 

 Forfattere ere bestemte, kunde de naturligvis kun erholdes 

 tidskilte i Form af kulsur Kalk eller, som af enkelte ogsaa 

 bindet, lidt kulsur Magnesia, men deraf følger ingenlunde, 

 at de med Nødvendighed oprindelig skulde forekommet i 

 Sovandet ■ under denne Form. ja dette er saa langt fra 

 sikkert, at jeg meget mere skulde være tilboielig til at tro, 

 at saa ikke er Tilfælde. Koger man nemlig Sovand i det 

 af Dr. Jacobsen beskrevne Luftadkogningsapparat, undviger ' 

 der. sum allerede for bemærket, meget sinaa Qvantiteter 

 Kulsyre. idet man kan fortsætte Kogningeii med vexlende 

 Afkjoling en hel Time uden at faa uddrevet mere end en 

 Brøkdel af Milligram pr. -Litre; Kogepunctet vil her i 

 Begyndelsen ligge meget lavt. men stiger, efterhaanden som 

 den iiudvigende Luft og den dannede Vanddamp forøger 

 Trykket, meget hurtigt, saaledes at jeg allerede under den 

 første Halvdel af Operationen bar observeret en. Tempera- 

 ratur ai' 89° ( '. Naar saaledes de i Søvandet indeholdte 

 sure Carbonater vise en saa haardnakket Modstand mod 

 Decomposition, at de i en hel Time skulde saa godt som 

 aldeles uden Virkning kunne udsættes for en Temperatur 

 al' omkring 90° (.'., da synes mig denne Egenskab -at passe 

 aoget bedre paa surt kulsurt Natron end paa sur kulsur 

 Kalk, og det vilde desuden falde vanskebgt at forklare 

 Søvandets tydelige alkaliske Reaction, medmindre man kunde 

 antage. at Carbonaterne i det Mindste for en ikke ringe 

 Mel bestod at Alkalisalte. 



Med Hensyn paa Qvantitetén af dr i Sovandet fore- 

 kommende kulsure Salte, da stemme de derover existerende 

 Opgaver meget daarligt overens, di' lyde i Regelen paa 

 Spor undertiden endog paa Intet, medens der ai' enkelte 

 igjen er opført forholdsvis store Mængder. Saaledes tinder 



decomposing when boiled "neutral carbonates. arises from 

 the slow reciprocal action of the carbonates and sålts of 

 magnesia it contains. and the properties observed by Dr. 

 Jacobsen in sea-water must therefore to a gr.eater or less 

 extent distinguish all mineral waters containing magnesia 

 compounds, or. according to Rose. in his statements quoted 

 above, all solutions of 'salts, prqvided they contain, exclusive 

 of sodium. potassium. lime. barium, and strontium, also 

 soluble salts of some one of the weaker hases, which 

 along with carbonic acid form inconstant combinations. 

 Hence, this circumstance clearly -shows, that of the nu- 

 merous methods devised for determining. in mineral waters, 

 the relative proportion of free carbonic acjd and that 

 present in carbonates nearly all are. when. magnesia is 

 present, unreliable, since for the ' determination oi' the 

 carbonic acid present in carbonates. eitlier the residue from 

 evaporation or some other result of boiling is bad recourse 

 to, whicb has been shown to be inadmissible. 



Finally. it will not be out of place to notice the views 

 originally entertaiued with regard to the carbonates pr.esent 

 in sea-water. 



By the process according to whicb the earlier cliem- 

 ists determined these compounds. they could of course ob- 

 tain them only in the form of carbonate of lime. or. as 

 found by some observers, along with a little carbonate of 

 magnesia ; but ironi this it does not by any means follow 

 that they necessarily occur in that form in sea-water : nav. 

 1 am myself inclined to believe that such is not the case. 

 ( hi boiling sea-water in the apparatas described by Dr. 

 Jacobsen, very small quantities only of carbonic acid are 

 found to escape; the fluid niay be alternately boiled and 

 cooled for an hour together without liberating more than 

 a fraction of a milligramme per litre. The boiling-point 

 with this method will at hrst be very low, ]mt. on the 

 pressure being increased by the escape of the air and the 

 formation of steam, • rapidly rise: even in the first half of 

 the operation I have observed a temperature of 89° C. 

 The vigorous resistance to decomposition thus exhibited by 

 the bicarbonates in sea-water. whicb admits of their being 

 exposed almost without effect for an hour together to a 

 temperature of nearly 90° C, would rather seem to indi- 

 cate bicarbonate of soda than bioarbonate of lime: and 

 besides. the decided alkaliné reaction of sea-water would bé 

 difficult to explain unless by assuming the carbonates — 

 or a, considerable portion of them at' leasl — to consist of 

 carbonate of- soda and potash. 



With regard to the proportion ol' carbonates present 

 in sea-water. the results as vet obtained agree but very 

 iiidjffereiitly : the majoritj of observers lia ve detected traces 

 only or none whatever. wliereas some allege to have found 

 comparatively large quantities, as will be seen from the 

 followiug Table. 



