Roberts, Edwin

Roberts, L. B.

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Journal of the Arkansas Academy of ScienceVolume 1 Article 221941Crystals of an Insoluble Carbonate of CopperGrown under a Soda SolutionL. B. RobertsUniversity of Arkansas at MonticelloEdwin RobertsUniversity of Arkansas at MonticelloFollow this and additional works at: http://scholarworks.uark.edu/jaasPart of the Organic Chemistry CommonsThis article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0). Users are able toread, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking priorpermission from the publisher or the author.This Article is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Journal of the Arkansas Academyof Science by an authorized editor of ScholarWorks@UARK. For more information, please contact scholar@uark.edu, ccmiddle@uark.edu.Recommended CitationRoberts, L. B. and Roberts, Edwin (1941) "Crystals of an Insoluble Carbonate of Copper Grown under a Soda Solution," Journal of theArkansas Academy of Science: Vol. 1 , Article 22.Available at: http://scholarworks.uark.edu/jaas/vol1/iss1/2271CRYSTALS OF AN INSOLUBLE CARBONATE OF COPPER GROWN UNDER A1SODA SOLUTIONL. B. Roberts and Edwin Roberts, Arkansas Agriculturaland Mechanical College, MonticelloWhen an old fire extinguisher of the soda-acid type wasopened and emptied preparatory to recharging, several grams ofblue crystals were found in the bottom of the container. Crystalsof the same kind were later found in several other extinguishers.Some of these crystals were fairly large, weighing as much ashalf a gram each. Since the body of the extinguisher was of acopper alloy and the solution in the extinguisher was a practicallysaturated solution of sodium bicarbonate, the logical conclusionseemed to be that the crystals might be a carbonate of copper.Since the color is blue, and not green like malachite, itwas atfirst assumed that the crystals were similar to azurlte, the othercommon basic copper carbonate. However, the crystal form provedto be different from that of azurite and the color a lighter blue,very much the same shade as copper sulfate crystals.When the crystals were analyzed qualitatively, they werefound to be practically insoluble in water but very readilysoluble with effervescence in dilute acids. Copper and sodiumwere the only metals found and carbonate the only anion (withthe possible exception of hydroxyl, for the crystals, althoughpractically insoluble, were found to give a faint basic reactionwith litmus). There was, of course, the possibility of waterbeing present as water of crystallization.This led to the idea that the crystals might be sodium coppercarbonate and quantitative determinations were run for copper,sodium, carbonate, and water. Copper was determined volumetrlcallyusing Park's modification of the short iodine method. Sodiumwas determined gravimetrically by precipitating the copper (theonly other metal present), converting the sodium to the chlorideby boiling to dryness repeatedly with concentrated HC1, heatingto remove ammonium salts, and weighing the residue as sodiumchloride. Carbonate was determined by loss of weight on libera-tion of CO2, and water of crystallization was determined by theloss in weight of a sample when heated to 110 °C for an hour.The results of these analyses show a total of 94.6%. Thedifference may represent water of crystallization too tightlybound to be driven out at 110°C as in the case of 1/5 of the waterIn copper sulfate. penta-hydrate . The retention In this case of1/5 of the water of crystallization would account for approximatelythe difference noted. No attempt was made to test these assumptionsof retained water by heating to a higher temperature because of thepossibility that some of the carbonate might be decomposed.On the basis of the assumption that the difference betweenthe sum of the copper, the sodium, and the carbonate found and100% represents the total water, a formula was calculated to fitthe data. The formula 3CuC0 s .NaHC0 5.8H20 agrees with the dataPresented at the 1940 meeting71Journal of the Arkansas Academy of Science, Vol. 1 [1941], Art. 22Published by Arkansas Academy of Science, 194172very satisfactorily as is shown by the tabulation following:Substance Pound Pound Theoretical(Actual) (Water by difference)Copper 29.0 29.0 31.8Sodium 3.7 3.7-3.8Carbonate 42.0 42.0 40.1Water 19.9 25.3 24.1Acid H.2Total 94. 6# 100. 0# 100.0%The difference between 100% and the total of Cu, Na, and C03found might be thought to be due to hydroxyl except for the factthat the ratio of carbonate to metal demands the assumption thatbicarbonate is present. The fact that the crystals were grownin bicarbonate solution lends support to this assumption.The accuracy of these analyses was limited by the smallamount of material available for study and it must be understoodthat these results are only tentative and may be modified byfurther studies.72Journal of the Arkansas Academy of Science, Vol. 1 [1941], Art. 22http://scholarworks.uark.edu/jaas/vol1/iss1/22

Crystals of an Insoluble Carbonate of Copper Grown under a Soda Solution

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Crystals of an Insoluble Carbonate of Copper Grown under a Soda Solution

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