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November, 1939 AIRCRAFT ENGINEERING Workshop and Production Section Further Information Regarding the Paints Described Last Month TAD N the article published under this heading in TABLE 1 LE II th e October issue of AIRCRAFT ENGINEERING Temperatur e Temperatur e I it was not possible to give the composition No. Substance . of change . Change in colour . No. Formula . of change. Change m colour. of the "Thermocolor" paints developed by Deg . Deg . I . G. Farbenindustrie. In response to inquiries wo I (NH ) U O 200 yellow to grey cobal t ortho-phosphate 20 140 rose to blue 4 2 2 7 now give the following abstracts of two British 2 ( )4H (Ni(MoO ) )·5H O 180—210 whit e to grey Co (PO ) .8H O NH4 6 4 6 2 3 4 2 2 Patent s taken out to cover the process. 3 (NH )3H (Fe(MoO4) )·7H O 80 whit e to yellow 21 cobal t potassium phosphate 140 rose to blue 4 6 6 2 200 yellow to black CoKPO .H O 4 2 4 (NH ) PO .12MoO yellow to black 140—160 22 coppe r hydroxide Cu(OH) 160 blue to black 4 3 4 3 5 CoNH PO H O 140 purple-re d to dee p blue lead hydroxide with 145 whit e to yellow 4 4 2 PATENT SPECIFICATION No. 478,140 4.5 per cent . of H O 500 dee p blue t o pal e blue- cadmiu m hydroxide 24 200 whit e to yellow gre y Coloured coatings, the colour of which clearly 6 NiNH PO 6H O Cd(OH ) 4 4 2 2 pale preen to grey- 25 iron hydroxide FeO—OH 280 yellow to red-brown changes at definite temperatures, so that the green 26 basic copper phosphate 650 gre y to green 7 NH MnP O 400 violet to white temperatur e of the surface concerned may be 4 2 7 8 (Co(NH )6)PO yellow to blue 200 Cu(OH)2·Cu (PO ) 3 4 3 4 2 deduced from its colour, are useful in th e investiga basic copper sulphate (Co)NH )6)2(C O )3 210—220 yellow to violet 27 200 green to black-brown 3 2 4 !) tion of many scientific and technical questions. 3Cu(OH)2·CuSO ·H O 250—270 violet to brown 4 2 brow n to black 28 secondar y cobalt phosphate 190 blue to pale grey-blue A number of dyestuff pigments are already known 10 yellow to blue-grey (Co(NH ) )HP O 280 CoHPO4 3 6 2 7 which change their colour reversibly when the blue-grey t o pal e violet 20 lead carbonate PbCO3 2(10 whit e to yellow abou t 400 temperatur e rises above or falls below a certain 11 purpl e to black-blu e 30 cadmiu m carbonate C(1C03 310 whit e to brown (Co(NH )5Cl)Cl 190 3 2 31 285 whit e to yellow 12 (Co(NH ) Cl)SiF 200 purpl e to grey whit e lead 2PbCO3·Pb(OH) limit, bu t only a few ar e know n where th e chang e in 3 5 6 2 13 <Cr(urea)6)(Cr(CN)6) 140 green to brown 32 basic cobalt carbonate 250 rose to black colour remains once it has occurred. Pigments (composition not determined) 14 [Ni pyr ] (CNS) 135 blue to pal e green 4 2 with the last-mentioned property of changing 210 pal e green to yellow 15 [Cu pyr2] (CNS) 135 green to yellow colour are, however, frequently very desirable TABLE III 220 yellow to black because they allow certain statements to be 16 140—150 yellow to violet [Cr(NH ) ] (P O ) 3 3 6 4 2 7 Temperatur e mad e as regards the temperatures which have 220—230 violet t o pale blue No . Formula . of change. Natur e of change . 280 pale blue to brown occurred even although the temperature conditions 17 fCr(NH )5Cl]C O 260 red to black brown 3 2 4 hav e changed considerably at the moment of Deg. 18 ICr(NH )5Cl]S F 250 re d to black brown 3 1 6 observation. 1 CoCl ·2C H N ·10H O 35 rose to blue 1!) NH4VO3 150 whit e to brownish 2 6 12 4 2 2 CoBr ·2C H N ·10H2 O 40 rose to blue 170 brownish to black 2 6 12 4 I t has been found that compounds of metals COI ·2C H N ·10H O 3 50 rose to green 2 6 12 4 2 capable of forming coloured oxides, which com 4 Co(CNS)2·2C H N ·10H O 60 rose to blue 6 12 4 2 pound s on being heated split off at least one Co(N03) ·2C H N ·10H O 75 rose to purple 2 6 12 4 12 ma y also be used provided injurious influences by 5 6 CoSO ·C H N4·9H O 60 rose to violet substanc e belonging to the group consisting of 4 6 12 2 varyin g moisture are excluded. 7 NiCl ·2C H N -10H O 60 pale green t o yellow 2 6 12 4 2 ammonia , ammonia derivatives, water and carbon 100 yellow to violet I t has further been found that the temperature 8 NiBr2·2C H N ·10H O pale green to blue dioxide, are suitable for th e said purpose. 6 12 4 2 60 a t which the change in colour of th e said substances take s place can bo varied within wide limits b y using th e substances in isomorphous mixture with one or Nature of Pigments salts, ammonium double salts or amine s of elements more suitable substances. In th e case of ammonium capable of forming coloured ions, and also such In particular ammonium salts, ammonium double double phosphates and arsenates, there may be compounds of metals yielding coloured oxides as salts and ammine compounds of metals capable of used as mixing components for example ammonium contai n water and/o r carbon dioxide in a combined forming coloured oxides may be mentioned. Both double salts of divalent metals having a similar ion form, in particular compounds containing water ammin e compounds containing ammonia and radiu s t o tha t of th e meta l of th e initia l double salt. of crystallization, hydroxides, hydrated oxides, acid ammin e compounds containing organic derivatives For example pale rose coloured mixed crystals of an d basic salts and normal acid and basic carbon of ammonia, such as amines, diamines, urea and CoNH PO ·6H O with MgNH PO ·6H O change 4 4 2 4 4 2 ates . Substances belonging to both of the said pyridine ma y b e used. Such compounds, a t certain in colour t o rose-blue a t a much lower temperature groups, as fo example amines containing water of temperature s which are characteristic for them, tha n the cobalt compound alone ; in the case of crystallization and double carbonates containing give up th e ammonia , amines or th e like contained othe r temperature-indicating coloured substances ammonium , are also suitable. therein wholly or partially, a marked change in suitable partners capable of forming mixed crystals I t has now been found that contrary to ex colour thus always taking place. Thus for example with the coloured substance concerned may readily pectatio n certain substances which in their com from the grou p of th e ammoniu m double phosphates b e found, which partners themselves give no change position belong to both of the said groups have an d arsenates of divalent metals, as for example in colour upon change in temperature or which special properties which give them an intermediate manganese, iron, cobalt, nickel, or copper, cobalt ma y also themselves belong to the group of tem position between reversible and non-reversible ammoniu m phosphate gives a colour change at perature-indicatin g coloured substances. temperature-indicatin g colours. Such substances 140 deg. Centigrade from purple-red to deep blue. ar e compounds of nickel and cobalt which contain At about 500 deg. Centigrade, a second change in Solution for Pigments wate r of crystallization and also hexamethylene colour takes place, the colour changing from deep tetramin e in a combined form. At definite tem Th e temperature-indicating substances, either blue to pale blue-grey. Two temperature limits, peratures , these substances split off water of alone or together with other substances, may be i.e., three temperature ranges, can be indicated by crystallization, sharp, contrasting changes in colour the said substances alone. Many other of the said applied with the aid of a suitable binding agent, as thu s taking place. They arc therefore very suitable substances also have two temperatures at which for example solution of artificial masses or an a s coloured compounds for indicating temperature. the y change either because the ammonia or its aqueous alumina sol. They may also be used in Contrasted with the coloured compounds hitherto derivatives arc given off in stages or because other admixtur e with each other ; such a mixture then proposed, however, the change in colour may be allows of the establishment of a correspondingly kinds of conversion occur later. rendered of no effect by moistening with water, so increased number of temperature indications. Th e accompanyin g table gives examples of suitable tha t the coloured coatings may b e used again. In Th e following serves to illustrate how the substances together with the changes which they contac t with ordinary air containing water vapour, temperature-indicatin g substances according to th e undergo, bu t th e inventio n is not restricted to the th e said return to th e original colour takes place by presen t invention may be applied in practice : examples given in Table I. itself after some time, whereas in a dry atmosphere One part of copper-pyridine thiocyanate Also such compounds of metals yielding coloured th e changed colour remains. CuPyr,(CNS) is intimatel y mixed with three parts oxides as contain water and/or carbon dioxide in a Table III gives the compositions of a number of a 35 per cent. solution of a urea-formaldehyde combined form are ver y suitable for th e said purpose. of suitable substances of the abovementioned condensation product in a mixture of equal parts Compounds having chemically combined water are kind, the temperature in degrees Centigrade at of ethanol and butanol. This mixture is applied for example compounds containing water of which they change colour and the nature of the a s a thi n layer on th e oute r surfaces of a n air-cooled crystallization, hydroxides or hydrate d oxides, basic change in colour. explosion motor. When the moto r is operate d after salts an d also acid salts with oxygen-containing acids th e coating has become dry, th e latter indicates which can be converted for example into salts of thre e ranges of temperature on th e war m as well as pyr o acids by the splitting off of water. As Possibility of Repeated Use on th e cold motor. The place s heate d up t o 135 deg. compounds having combined carbon dioxide Although the said substances have considerable Centigrade preserve the original green colour; there may be mentioned normal, basic or acid solubility in water, they may be coated together those heated up to from 135 deg. to 220 deg. carbonates . At certain temperatures, which arc with aqueous as well as with non-aqueous film- Centigrade are yellow and those heated above characteristic for the individual substances, they forming substances, especially when indifferent 220 deg. Centigrade assume a black colour. give off water and/or carbon dioxide, a marked pigments, as for example titanium white, are change in colour thus taking place. presen t at the same time. The properties of the A number of examples for suitable substances PATENT SPECIFICATION No. 506,201 single substances may be modified in many ways of the beforementioned kind is given in Table II . by mixed crystal formation with other substances Th e specification No. 478,140 describes coloured Generally speaking, it is preferable to select given in the abov e table or with other isomorphous coatings capable of indicating temperatures, the temperature-indicating substances which are diffi substances. said coatings containing metals capable of forming cultly soluble or insoluble in water, but in many Mixtures of th e above-mentione d substances with coloured oxides, which compounds on being heated cases water-soluble and even hygroscopic substances each other or with other coloured compounds, split off a t least one substance belonging to the capable of indicating temperatures may also be group consisting of ammonia, ammonia derivatives, *Copies of the ful l specifications quoted in this article can be used in order to be able to establish a number of wate r and carbon dioxide. There may b e mentioned obtained from H.M, Stationery Office, 25, Southampton Buildings, temperature s with a single coloured coating. ammoni a compounds, in particular ammonium London, W.C.2, price 1s. each. 43 1
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Nov 1, 1939
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